In this industry populated by people, who have learned their craft by the seat of their pants, or from others who did the same, it is nice to know there is a place where quality workmanship and industry standards are actually taught. Dave Boyd, my business partner, and I recently attended such a school, so that when were are asked why, we would not respond, “that’s just the way we always have done it”.
David Tisherman and Skip Phillips with student
The school was taught by the renowned Genesis 3 Design Group. It is a joint effort by three of the finest pool designers in the world, David Tisherman, Skip Phillips and Brian Van Bower. It is the only pool and spa construction school in the United States that is accredited by IACET, the International Association for Continuing Education and Training. Genesis efforts, in offering this course as well as a number of other courses, that range from the technical aspects of the pool industry to designing the most artistic pools in existance, should be lauded. As a by product of their work, they have also created a network of designers and builders who are continually pushing the bar, setting the standards higher and higher!
In class with civil engineer, Terry Brannon
Having been in the industry for almost 20 years, first as a service professional, then as a pool renovator, designer and builder, I have seen first hand the poor standards most pool companies hold for themselves. It is a said fact these companies are not even aware of the standards set by fine organizations such as the American Concrete Institue or the Ceramic Tile Institue of America, let alone make their project specification adhere to their basic guidelines. Furthermore, I have previously attended certain trade association’s classes, and have been far less than impressed. With some associations, it seems they are more concerned with giving out ludicrous awards and patting themselves on the back, than in the delivery a quality product. It’s no wonder the pool industry has such a bad reputation.
Celebrating Success
Wanting to establish our company as above the average, we decided to complete the requirements of this course, which was followed by a thorough examination, given according to IACET standards. Both Dave and I learned a significant amount of information and were able network with a number of like-minded professions. More importantly, we both passed the examination. In the category of “tooting my own horn”, I was able to bring home the all time best examination score, and be quite proud of it!
In our previous articles we discussed the design and layout of the pool, its excavation and steel reinforcements as well as the initial plumbing and electrical work. All of this work has been leading up to the single most important construction component, the shell of the pool, which surrounds the body of the pool. It is made of pneumatically applied concrete, shot at high speeds, encapsulating the reinforcing steel, to give remarkable strength. It’s quick to install, versatile, in that it can conform to almost any shape and compared to poured in place concrete is very economical. Yet without proper technique being applied at the time of the shot, the entire future of your pool will be problematic.
With all the preparatory work out of the way, the day has arrived when your new pool will be shot. The process is referred to as “shooting” because the materials are literally blasted into place at high velocity, over 100 mph, which is good! This “blasting” is part of the reason that the shell can develop such great strength. Other contributing factors will depend upon the type of shooting that will take place. There are two types. Although the names have been used interchangeable by some in the industry, which causes much needless confusion, both types are technically known as Shot-Crete or pneumatically applied concrete. With either type, the crews use air as the primary driving force which places, then compacts and consolidates the concrete mixture. The differences are that some crews use a dry-mix, commonly referred to as “gunite”, which is delivered from the trucks, forced through large hoses by air pressure, then combined with water as it leaves the hose nozzle. The other type of crew use a “wet-mix”, commonly referred to as “shot-crete”, which is combined with water prior to being pumped by a concrete pump through the hose, then is forced by air from the hose nozzle. For more information on the differences, read my article “Shot-Crete, Gunite what’s the Difference?”
Shotcrete Truck Setup
As the crews arrive, you will notice they are accompanied by several large trucks. The number of vehicles depends on which type of crew has been chosen. A wet-mix crew will arrive with at least a concrete pump and a large air compressor. They may mix the concrete on-site, which will require a vehicle to hold the raw concrete, another the aggregate, usually sand and pea sized gravel, and a mixing unit to combine these items with water. This is commonly done in area that experience high temperatures and are too far from a local concrete batch plant. As you may know, concrete, once mixed, must be placed within 90 minutes. So on-site mixing is sometimes their only option. A dry-mix crew will have a vehicle to hold their dry mixture and of course a very large air compressor. The larger compressor is required because the air is not only used to force the mixture into place, but to also move it through the hose. By contrast the wet-mix is moved through the hose by a pump, not air.
Below is a video of a wet-mix truck in place:
With the truck ready, the crews prepare the pool, confirming several key factors. First the pool must be level. Hopefully the previous crews properly leveled the work, the wood panels which outline the pool shape. If not, last minute adjustments must be made.
Second, the elevation must be correct. This measurement establishes a necessary reference point so that after all the work is complete, coping, tile, deck, etc, the finished product is at the appropriate level in relation to the house, or other buildings. Once the concrete has been set, “out-of-level” and “elevation” adjustments are much harder, if not impossible to make.
Third, the forms and steel are checked for sturdiness or rigidity, neither must be allowed to shake or otherwise move as the concrete is being shot. Vibrations and movements prevent the concrete from properly attaching to the steel and possibly create hidden voids, or pockets of air, which will weaken the structure. Insist that your builder provide adequate form work. A weak form will only hurt the process. If a spa is part of the plan, make sure the builder installs a form board between the pool and spa. Do not let them simply hold a “peg” board, or have it wired in place by bailing wire to the reinforcing steel. A solid form should be built. Once the wall which separates the pool and spa is shot and partially set, the form can be removed before the rest of the spa is shot. Failure to do so might mean a weakened mixture and voids behind the steel.
Fourth, they will confirm the thickness of the completed beam. Here the crews will confer with the builders plans to make sure the top of the pool wall, the beam, will be as thick as designed. Typically this is about 12″ wide. The importance of this cannot be overstated for two reasons. First, the beam must be sized as designed to allow for the later installation of finish stone work, and the allow the appropriate integration with any new decks, etc. Second, and no less important, the beam, and not just the beam on this point, must be wide enough in all places to properly “encapsulate” the steel. As we have all observed steel will rust, an normal process of oxidation when air, steel and water meet. Rust, although rarely good, is very bad in pool steel reinforcement. Particularly if the rust finds its way into the pool and shows itself as a dark red stain on the pool wall. In order to reduce and hopefully eliminate this process, the American Concrete Institute specifics where concrete is exposed to earth or water the steel should be encapsulated by at least 3″ of concrete. Unfortunately I have seen problem pools where the steel has only 1/2″ of concrete between the steel and the water. This problem can not be corrected later, only managed. It is a costly and avoidable problem, if the pool is shot correctly.
Setting the Guide Wires
To aid the crews as they are shooting, they typically install fine guide wires. The attached photo shows just such a wire, although the wire, being about the thickness of a piano wire is hard to see. Unlike poured in place concrete, which has forms forms on both sides, to contain the fluid concrete, shot pools have forms on only one side. Newly shot concrete is just shot is stiff enough to maintain its basic shape, so two sides are not needed. However, the guide wire helps the crew see where the “other” side of the concrete needs to be.
Partitions to Reduce Overspray
Other preparatory work includes placing screens to help prevent concrete over-spray from reaching the home or other structures. Concrete over-spray on a home would not be a good thing! There should also be a decision on what to do with the rebound and trimmings. Rebound is the term for the concrete mixture that bounces off during the shooting process. It is important to note that the “bounced” mixture is concrete poor, meaning it is usually the aggregate, sand, that bounces, most of the concrete that was part of the mixture will stick, making the rebound mostly aggregate. So rebound must not be reused. It should be collected and discarded. As a point of interest the dry-mix process always generates more rebound than the wet-mix process. A small amount of rebound is usually not a problem, but a large amount will have to be removed from the site. The mixture, though concrete poor, will still harden, and have to be discarded.
Troweling the Wall
The term trimmings refers to excess concrete, more being shot than is actually needed the crew will trim the concrete to the required shape, letting the trimmings fall. Trimmed concrete can be reused, as it is not concrete poor, however, it must be properly compacted and consolidated into place. Most crews find places in the floor for the trimmings. It is not recommended that trimmings be used in the cove, where the wall meets the floor as this is a structural stress point. This however is where trimmings typically fall. This requires the trimmings to be moved to a less stressful place on the floor.
Below is a video of a pool wall being trimmed:
With all the prep work complete the shooting begins. The long hoses, running from the truck to the pool, terminate at a nozzle, which the crew member, called the nozzle-man, aims the hose, directing the concrete flow. He begins at the cove, base of the wall and floor. The extremely important area, must be solid and well shot. The concrete is built up from this point making the walls, benches and other components. The floor is usually the last place to shoot. Sometimes the process will be stopped as the crews moves between the main pool and the spa, fountain or other structure. Always the nozzle-man maintains a flow at downward angle, moving back and forth building up the concrete toward the final shape.
Finished Shell
As mentioned earlier regarding trimmings, the concrete is built up to a level greater than needed, then trimmed back to the desired shape. The process requires patience and an ability to see shape of the final product. All the internal components have to be shaped, the steps, benches, love seats and shallow lounge area. In addition the pool fittings, where the plumbing penetrates the wall has to have special attention. At each location an indention is shaped around the protruding pipe to provide room for the “fitting” which will be installed later. The lights, skimmers and main drains will have similar attention. Finally you may notice one or more “weep” holes, voids in the concrete where ground water can move if excessive rain occurs before the pool is completed.
The entire process for a small pool should only take a few hours, obviously more for larger one. Large commercial projects can take several days. Prior to the shell, the shape of the pool can only be imagined, based only on the design drawings and the designers descriptions. Now, the shell having been shot, the pools shape becomes clear. One step closer to a completed pool!
In our previous articles on pool construction we have discussed design, required city permits, excavation and steel reinforcement. We are almost ready for shooting the pool shell. However we most consider that some tasks required in the construction of must be at least partially performed before the pool shell is built, namely the plumbing and electrical work. Both of these tasks will not be fully complete until much later in construction process. Yet where either of these tasks will penetrate through the pool wall, the must be laid before the shell is installed.
Skimmer Plumbing
The easiest explanation of the plumbing is built on the understanding that the water in the pool completes a circuit, which is known as the hydraulic system. It must first be pulled from the pool, filtered, heated if desired, perhaps even treated chemically, then returned to the pool. This process begins with the water being extracted through the skimmers and the main drains. The skimmers which mounted at the water level are designed to catch leaves and other floating debris which is collected in a basket. It is advisable to have more than one skimmer installed in your pool, particularly in environments with lots of foliage or on larger pools. Better pool designers and builders will insist on at least two skimmers on every pool and increase their number as the situation warrants. The exception to this is on pool designed with either a “vanishing edge” or a “raised perimeter overflow”. The vanishing edge pools have at least a portion, usually an entire side, where the water spills over the wall of a pool and into a trough or catch basin. Raised perimeter overflows are pools partially lifted out of the ground. Here the water spills over the entire perimeter of the pool, usually into a hidden trough which surrounds the pool. Both of these types of pools offer dramatic visual effects and usually have no skimmer. This is because the trough or catch basin often acts like a huge skimmer. These pools stay remarkably clean!
Main Drain Plumbing
The main drain, which is a misnomer, is currently the source of much saftey discussion. It really should not be called a drain since it does not allow you to drain your pool. Neither should it be considered the main source of water for your pool equipment, in that the equipment should only rarely receive all its water from these drains. Technically these devices are referred to as “suction outlets”. It is vitally important that the hydraulic system of any pool be designed with care. Recently congress passed the Virginia Graeme Baker Pool and Spa Safety Act. This law purpose is to reduce the danger of these outlets by requiring outlet covers pass strengant testing requirements and that outlet placement meet certain standards to reduce the likely hood of someone becoming entraped by these outlets. However there is no requirement that a pool actually have these suction outlets. Constructing a pool without them altogether will more than just lower the possiblility of a suction entrapment, but will compeletly eliminate it! The photo pictures placement of these suction outlets as currently required. If you look carefully you will notice that the installation has altered the steel layout which will have to be corrected before the shell is shot.
Wall Plumbing
After the water has been filtered and otherwise treated, it is returned to the pool via the returns fittings attached to plumbin which extends through the pool shell wall. Prior to the shell construction, the plumbing for these returns must be placed and secured into position so that they can not be moved as the shell is placed.
Electrical Bonding
A similar process must be completed for the electrical work. Codes require that the steel be tied electrically to the electrical system through a bond, which is a wire that runs from the pool equipment and to the pool structure and is tied in several places directly to the stell reinforcement of the pool. Since most pools are constructed with an underwater light the conduit for the light must also be installed at this time.
Later the more plumbing and electrical work will have to be completed. But with the inital work complete, specfically where there work extends through the pool wall, the pool is now ready for the next step, the shooting of the pool shell!
To review a FAQ (frequently asked questions) Report prepared by the Health Department of the State of Texas regarding the Virginia Graema Baker Pool and Spa Safety Act - Click Here!
It should be noted that not everything must be the same. Sometimes even simplest changes, such as the direction of the tile can make all the difference in the world. Doing so may add visual interest by emphasizing a new direction for the eye to follow. On a recent project we used a diagonal placement of tile to achieve a stunning look over what was a dated and overwhelming feel of the brick!
Brick can be a wonderful construction material, but in this case, the builder used too much brick. In dealing with an natural elevation change present in the yard. The builder created a wall, raised bond beam, to retain the soil of the yard, which sloped toward the rear entrance of the home. This raised area was now home to a spa, itself raised slightly, and a small entertaining area. This area space is accessed by a series of steps to the left of the spa. The wall began with the steps, ran underneath the spa and extended to the far side of the pool where it similarly descended back to the elevation of the home. For all of this the builder used a red brick, both as coping on the pool wall and as a face to the wall itself. The only exception being a vertical band of tile below the spillway of the spa. The effect of this much dark brick was to overwhelm, putting the entire backyard out of balance.
In approaching this project, our client asked us to update the pool’s overall appearance, especially the brick wall. To do so required numerous visits to various material suppliers until we found a coping treatment and tile selection that matched the clients taste while lightening the pools appearance.
After much searching and deliberation, we finally settled on a 6″ x 6″ light tan and gold tile, which came with wide variation in color for the pool water line and a matching 12″ x 12″ for the wall. The tile was complemented with 24″ bull-nosed travertine coping. Travertine was also used to create a new extended spillway.
Surface Preparation
The existing brick face was left in place, but was coated in mortar. In doing so we were creating a new tile beam, which is usually necessary in renovation work, but particularly in this case. Over this rough brick we needed a smooth and level surface for installation of the tile.
Centering the Tile
Our 12″ tile was centered on the wall between the water line and the spa spillway. The initial tiles set are the most important, as they establish the pattern for the entire wall. We chose to lay the wall tile on diagonals. This would create a simple but interesting pattern, which would contrast nicely with the lines of the pool.
Pattern Continued around Pool
The actual setting of these wall tiles was time consuming, requiring a number of cuts in the tile, particularly where the wall angled in and out from the pool. After the tile was set a topaz colored grout was applied. This color matched perfectly with the tile making the grout lines all but invisible.
Wall Tile and Spillway
Eventually the wall was completed along with the coping and water line tile. The effect new tile, particularly against the against the color of the water was visually stunning!
In a recent renovation project, we had the opportunity to completely change the appearance of a pool by both the choice of our material, and by the attention to detail in its application. Originally the pool was surrounded by red brick. There was red brick everywhere, as coping to the pool beam and as a face to the wall of the pool. While I like brick as well as the anyone, in this application, it was not only dated, but very over-powering. It also created maintenance issues as the brick absorbed water from the spa spill-over, which left white calcium deposits and algae. Finally, the installation was less than stellar, in that they created a “reveal” on the face of the riser next to steps which had no such reveal. The placement of the reveal, which is the shadow line created by materials cantilevered, overhanging other materials, is important. It is often used to “reveal” elevation changes, or simple for the architectural value it visually creates. In this case the builder’s choice resulted in leaving an ”unfinished” face of the brick exposed, making me wonder, what were they thinking?
Surface Preparation
Our choice of material was travertine, which is one of the best materials to use around pools. Not only does travertine typically have a high compression strength, but it is one of the few materials whose traction coefficient increases as it gets wet. This means you are less likely to slip on the travertine when you exit the pool dripping wet, then when you entered dry. Rather than install the travertine in the same way the brick was installed, we decided to install the coping on both the horizontal and vertical surface of the risers. The stone was cut on miters for a simple clean, continuous look of the beautiful stone.
New Coping without Reveal
The resulting finish eliminated the reveal, making the surface flush with the face of the seeded aggregate deck work. Now the deck and coping are consistent with no unfinished sides exposed. Most materials are finished with sides that intended to be exposed and sides that are “unfinished” meaning they are intended to be hidden because they will be masked by the bonding agent or where they but against joining materials. This was not true before in our original pool and was corrected in the new coping work.
New Reveal on Coping
The reveal is now on the pool side and is consistent with the rest of the pool coping. Travertine is a material that is usually cut and polished creating a smooth and clean appearance. Our installation emphasized that detail, played off it and the overall result was impressive!
It is amazing, if not mind boggling, that something as big and as heavy as a concrete deck can move. One would think that something of this sort, when constructed would stay put. However, decks can and do move. Sometimes just slightly, with only slightly noticeable effects, and other times by several inches or more, where they are at the least a visual annoyance and perhaps a hazard.
Wide Expansion Joints
The reasons decks move are varied. All the reasons are built on the understanding that the deck is not moving alone. If a deck moves, it is likely that the soil underneath the deck has moved as well. The soil, must be thought of not as a solid material, but as a slow moving fluid. We have all noticed soil can appear to grow over concrete that is both adjacent and slightly lower in elevation than the body of the soil. Generally the soil, which is loose combinations of particles in varied size, is bound and held together by only gravity and the root systems of it’s plant life. If the soil is located on a level plane, the movement will be generally downward, thus the soil, overtime will become more compacted. If the soil is on a slope, the soil will move with the force of gravity down the slope. To complicate things, much of the soil in north Texas is made up of expansive clay. The volume of this soil is constantly being changed as it takes on and gives off moisture. Basically the soil is going through constant cycles of growth and reduction. Some soil is considered unusable for structural purposes, without special engineering, as it will not support the weight of heavy objects. Normally the weight of objects is transmitted down and outward from its base, but some soil, those with a high plasticity index, acts like small ball bearings, and moves out from under the object causing it to shift and sink.
These factors can generally be overcome, if they are known in advance of the construction process. This is why I recommend that before any building be considered, particularly where it represents a substantial investment, that the soil be tested professionally to determine its makeup and weight bearing capacity. If the condition of the soil is known and problems exist, they usually can be remedied. Possible solutions include compacting loose soil, removing bad soil, and replacing with compactible soil, proper foundation/footing sizing and placement, and to reach down to stable soil, piers and pilings.
Deck Falling Away
Where the deck has fallen away from the pool, the cause is likely the supporting soil was not compacted correctly. The picture shows a deck on reasonable level soil that over time settled away from the pool. The edge furthest from the pool had the most freedom and fell by several inches. The edge along the pool was likely tied structurally to the pool. The result created a hinging effect where the deck now leans. Note that on the accompanying raised deck section the deck movement is such that the brick and tile fascia have broken loose and and are no longer level with the pool structure.
Wire Mesh Reinforcement
In a recent renovation project we found the deck was moving away from the pool, sometimes just horizontally. In some sections, the deck sections had separated from each other where one section was 2″ higher than the adjacent section. In this particular case there had been little or no attempt to tie the sections together structurally. In fact, the only reinforcement existing in the deck was a wire mesh, insufficient in this case.
Structural Cracks
In some cases, where the soil has moved, the deck is unable to move, it responds differently, by cracking. A structural deck crack is one that exist all the way through the concrete structure and indicates a complete break. This type of crack is a failure of the concrete to resist external forces to bend. In some cases there was insufficient or incorrectly laid steel reinforcement within the concrete to withstand normal, expected forces. Other times, however, the deck was engineered with the assumption the ground would be stable and sufficiently compacted . If this was not actually the case and the supporting ground settled beneath the concrete, then the concrete would then have to span across the gap created by the settled earth, a condition it was not designed to withstand.
Lastly, I should point out there is a movement of decks and other concrete work which is not related to the soil. It is expansion and contraction. In this case the deck is not so much moving, as in away from or towards something else, as much as it is getting ever so slightly larger when it warms and then smaller when it cools. This type of movement is anticipated by the integration of isolation joints or expansion joints in the concrete. These joints are actually separations in the concrete works, usually filled with a flexible material. The concrete sections should not be structurally tied together unless designed by an engineer. Keeping them from from moving apart will be accomplished by properly addressing any soil concerns. Failure to install these isolation joints at appropriate locations can often cause their own problems, such as cracking where two sections, both expanding moved against each other.
Have you every wondered why concrete is such a great and versatile building material? Probably not! Neither have most people. Nevertheless, if you’re considering a pool or spa, you should understand a few things about this wonderful material. Why? Because the concrete, specifically reinforced concrete, will be the frame work on which your pool is built. Properly installed it will last for decades. Improperly installed, problems will likely appear in short order, sometimes requiring repair or complete re-installation of the entire project. The elements which make concrete so strong lie inside the concrete and are virtually undetectable once the concrete is installed. It will pay you great dividends to know a little about concrete, before the construction process begins so you know if your project is being built correctly.
The Pantheon in Rome
For background purposes, you should know concrete has been used as far back as Roman times. In fact the dome of the Parthenon in ancient Rome, which is still standing, is one of the best examples of early concrete construction. Early builders utilized concrete because it developed the strength of stone, but could conform to almost any shape they needed. They did recognize its limitation however, in that it could not support great spans without extra support. The early great buildings were limited in height and interior spacing. Walls were supported by great buttresses to withstand the forces of the building domes and roofs.
It was understood very early that reinforcement was needed to properly support walls and other structures. As far back as in the construction of Greek Temples, lead, a very soft but malleable metal, was used to help hold the stones together. Later, cast iron was used. It wasn’t until the 19th century that concrete construction possibilites began to explode. In 1892 Francois Hennebique using steel devloped a system of reinforced concrete. The combination of the inherent compression strength of concrete and the outstanding tensile strength of steel allowed for buildings to take on great heights and expanses.
Pneumatic Concrete - Shot Against the Ground
In pool construction things further changed with the advent of pneumatically applied concrete. Sometimes this is called gunite or shotcrete. But make no mistake, they both are concrete. What makes them great for pools is the way the concrete is applied. Essentially the concrete is forced out of a gun at high velocity. This allows for two things, first that the concrete can be immediately consolidated and compacted when properly applied, two very important elements of strong concrete, in that the concrete becomes a solid body, without voids or hollow spaces which can greatly weaken any concrete. The second thing pneumatically applied concrete allowed is for the shape of the pool to be constructed virtually “formless”. Prior to this time all concrete was poured into forms, constructed wooden boards on two sides. The wet, fluid mixture was poured between the two forms where it remained until it hardened. This required that the pools take on basic, fairly easy shapes to construct in the forming process. Pneumatically applied concrete can be shot directly against the ground or a one-sided form. This greatly simplified the forming process and allowed the shapes to be limited only by the designer’s imagination and the excavator’s skill with the digging equipment.
Along with this new found freedom in shaping pools, also came cost savings. Since pool walls need not be formed so completely, the cost of constructing a pool decreased, creating an explosion of swimming pool ownership across the world. And as pools became more common place, the desire for creativity and expression has lead us to incredible possibilities in shaping your pool.
Steel Reinforcement - Notice the Deforming Marks
It’s the steel properly sized and distributed inside the concrete that gives the concrete it’s incredible strength. Reinforcing steel bars, commonly shortened to “re-bar”, are produced in long “deformed” bars of various sizes. The deformation on the bars refers to the raised markings on the steel, which creates extra surface area and texture to increase the mechanical bond between the steel and the concrete. The steel is laid out in a grid pattern and supported so that when the concrete is applied, the steel will be ”encapsulated” inside the harden mixture. Encapsulation is important since it provides a measure of protection between the elements and the steel, preserving the strength of the steel. In pools, according to the American Concrete Institute, there should be a minimum of 3″ of concrete between the steel and the water. Failure to maintain adequate encapsulation will not only weaken the steel, but the water, will penetrate to the steel, and likely bring particles of steel back to the pool surface leaving a horrible rust colored stain. This reinforced concrete is now able to withstand forces greater than either the steel or the concrete could withstand on its own. The concrete, brittle without the steel, now resists great forces. The steel, easily subject to corrosion from water, is protected by being encapsulated inside the concrete.
When considering the construction requirements for you pool, you should be aware of several vital things:
The steel must be adequately sized. On a typical residential pool, the basic grid pattern is created out of #3 (3/8″ diameter) steel bars. At various points around the pool the size will increase to a #4 (1/2″) steel bar. The beam of the pool, which is probably easier to think of as the top rim, requires the most strength. This makes logical sense, when you consider that the rim of a cup or bowl is usually thicker than most other parts. It is at this point, called the beam, that the pool must be at its strongest. Typically, in north Texas, four #4 bars will be spaced together in concrete thicker than in most other places of the pool. Larger pools or sections subject to great stress may require even larger steel.
Bending Steel to the Pool's Shape
The steel must be properly spaced. On a typical residential pool, at least in the north Texas area, most builders are using a 10″ spacing in both directions, meaning the pattern of steel creates squares throughout the body of the pool, where no square is larger than 10″. At various points in the pool, where additional strength is required, this spacing between the steel will decrease. For instance the beam, being one such stress point, will commonly made up of at least three #4 bars running parallel around the rim with a spacing of approximately 2″ to 6″ apart. This is known as a 30 pound beam, meaning it should be able to withstand earth forces of at least 30 pounds per cubic foot. Four #4 bars in a beam will make up a 45 pound beam, the most common type of beam in North Texas due to our expansive soils, and six #4 bars make a 62 pound beam. Where the pool wall meets the floor, another point of stress, it is common, and usually very necessary, to see an additional steel bar added to the spacing, creating a 10″ x 5″ pattern of steel. The grid, what ever the spacing, will conform to the shape of the pool, moving around corners and over benches and tanning ledges.
A Double Curtain of Steel for the Spa
Freestanding walls require more steel. A pool wall must endure both the force of the water inside the pool pushing outward and the force of the ground pushing inward. Where a wall abuts native, undisturbed soil, due to the ground absorbing part of the load, the strength of the wall need not be as strong as a wall which has no support and must support the entire weight of the water. These walls, known as “freestanding” walls are sometimes required in places such as the wall between the pool and spa, or on a hillside where the ground slopes away from the pool. Internally these walls will require more steel than other walls and may sometimes even require a double curtain of steel.
The steel must be secured. Where the steel crosses other pieces of steel the intersections are secured with tie wire. This keeps the steel from moving out of its required position and more importantly keeps the steel from vibrating when the pneumatic concrete is shot into place. If the steel vibrated this would likely create voids in the concrete, weakening the structure. Steel rods are usually manufactured in 20′ sections. For this reason it is likely that more than one strand of steel is used to make a pass from one side of the pool to the other. Where two sections of steel meet, there must be appropriate overlap. Usually with #3 bars the overlap is at least 18″ and 24″ with #4 bar. Also make sure where the various piece of steel come together that there will be sufficient room for the pneumatic concrete to be applied around and behind the steel. Failure in this area will create shadows, or voids which will weaken the resulting concrete.
At this point you may be wondering who determines if the steel has been adequately sized? Or who determines the appropriate steel spacing? In some cases the builder may feel sufficiently experienced to make such determinations. However, it is my policy to have every pool plan reviewed by a qualified structural engineer. An engineer will use the information revealed on a soil’s report together with the structural requirements of the pool plans and layout the requirements for the steel. It is his job to determine that pool footings are sufficiently sized and placed and that an appropriate steel schedule has been written for the pool.
In summary, it is reinforced concrete that will make possible the pool and spa of your dreams. But make sure that you trust your builder, that he knows and understands the requirements necessary for your pool to last, giving you years of trouble free existance. If in doubt require that his plans be reviewed by a qualified engineer.
If you have just spent a large amount of money creating that perfect backyard experience, that last thing you should want is to notice the Details that should remain HIDDEN. You should see the beauty of the water, the color and feel of the stone, the brilliance of the fire reflecting off the water, or perhaps the combination of all these things. But you should NOT notice the necessary, but more mundane aspects of the project, such as the deck drains! Things such as this are required, necessary for quality functioning of the space. But why call attention to them. I have seen numerous installations, where builders have gone to the trouble and expense to add “brass” drain covers to their installations. Brass! I love brass, but the inherent beauty of this metal does not disguise the fact that it covers a drain. Instead it more importantly calls your attention to the drain. Granted a brass cover is better than a plastic drain cover, which are horrible obvious. However, there is altogether a better idea, HIDE the drains!
Hidden Drain Cover
Proper drainage is very important in most installations. It allows for excess water from splashing in the pool or from rain storms to be diverted to more appropriate areas. If no drainage is provided, the excess water is likely to find its way into the pool, carrying dirt from the deck. This can cause extra and unnecessary pool maintenance. The drainage is usually provided by buried drainage lines which are installed with an adequate amount of slope allowing gravity to pull the water and small debris down to areas away from the deck and pool. The drain covers carry the important function of restricting larger debris, which may clog the drain lines, from entering the system.
Drain covers are typically round covers with small, perhaps 1/4″ size, slots cut into the covers. As mentioned before the plastic and even the brass covers rarely blend into the surrounding deck material. However in a recent deck project, I found and installed a new drain cover which virtually hides this detail. The covers are indeed round, but are recessed into the deck and have a center section that can be filled with the same material as the rest of the deck, concrete or even stone, creating a virtually seamless appearance across the entire deck. The only thing that is visible is the small 1/4″ slot that surrounds the center piece. It is as hidden as possible and still be allowed to function as a drain cover.
Filling Drain Cover with Decorative Concrete
The installation of these covers should be considered from the start of any deck project since they must be installed prior to the deck installation. The underground system must be installed first. If concrete is to be poured, the drain covers, installed over the drain pipes must be at the required elevation of the finished deck. Next the concrete or decking material is installed. At this point the same material should be installed into the center section of the drain cover. The photo shows decorative concrete being poured into these sections. In this case the decorative pattern and color must also be applied. This makes the center sections blend into the rest of the deck.
With the installation complete, the drainage covers no longer call attention to themselves or distract from the beauty of the deck! More importantly, you can relax, enjoy your new creation, and pay attention to the details you will really want to see.
For a look another look at this detail, check out my video:
Any good design, must serve its function however that may be defined. Otherwise it is not fulfilling its purpose. I was recently retained by a client, to make a non-functioning space usable again. They had a social area by their pool, but the area, as currently designed was non-accessible to a family member. In its current form the social area was raised above the current pool decking by one step, and was created out of wood. It had been built by the previous owners, so all original design thinking was lost. For the current owners, it was virtually unusable to a family member who needed wheel chair access. Each time a function was held in this area, he had to be lifted, chair and all, above the normal deck grade an onto the wooden area, time consuming and a bit precarious.
The clients wanted the wooden deck area removed to make room for a new area, level with the existing pool deck, and slightly larger in size. They had toyed with the idea of using pavers to accomplish this task, but finally settled on decorative concrete, for its stability and ease of maintenance. They were not sure how large it should be or what new shape it would take. With the layout in mind and ideas from the clients, I went to work.
Deck Perspective Drawing
The design I came up with for the new area would be approximately 1/3 larger than its previous version and for visual continuity would take on some of the same angles used in the pool. The pool was essentially a figure eight in shape, but all the pool angles measured 45 degrees. So the new deck area would have 45 degree angles in several places to blend in better with this original design. It was important that the new deck look as if it belonged, and not as if it were a haphazard addition to the pool areal. The change of material, from an exposed aggregate, of the existing pool deck, to a decorative concrete in a stone pattern was not unusual, since the differing materials would indicate a change in function, from pool circulation to relaxed social area. The stones pattern would be an “ashlar” slate, which is made up of random pattern of squares and rectangles, lined in courses, running parallel to the predominant pool edge of the section. The color choices would be largly tan with some brown and red highlights. In order for the client to see what I had envisioned, I rendered a perspective of design.
Cutting Off the Raised Bond Beam
The first task in creating this new area would be removing all elements that extended above the desired grade, the wood deck and what was known as a “raised bond beam”. This beam was essentially a second row of tile in the area of the wood deck. This second row had been virtually hidden under the wood, yet once the decking was removed, the concrete and tile projected up, higher than was desired. This raised beam which was built on and attached to the beam, or wall of the pool, had to be removed. For this a concrete cutting specialist was brought into the project. The area was stripped of the wood decking and tile work. The cutting crew brought a large saw which was mounted to the pool structure. The saw made rather short work of this 15′ section. It was also necessary to remove several small sections of the pool decking. This was to create a bit of symmetry from one side of the pool to the other, particularly where the new deck was to meet the existing deck. Once the cutting was complete the concrete debris was removed.
New Deck Forming and Reinforcement
Next the ground had to be raised with fill dirt and properly compacted. It is very important to properly compact the new “fill” soil before the new deck is poured. Otherwise the soil will compact on its own over time leaving the new deck work unsupported. This can cause the deck to shift or move with the compacting soil or crack under stress it was never designed to endure. The new deck area was “formed” and reinforced. By forming I’m referring to wood borders which will define the shape of the new concrete deck. Concrete when freshly mixed is in a “plastic” state, thick yet quite pourable. It has to be held in the desired place by these forming boards until it has harden sufficiently to retain its shape. The reinforcement is required to give concrete its enduring strength. Inherent in concrete is a high compression strength, meaning it has great ability to resist compacting forces, such as the force of weight applied downward upon the deck and the force of the supporting ground pushing up on the deck. However if the two forces are unbalanced and produce a twisting motion, for example, non-reinforced concrete can easily break apart. This is why, since the process was invented back in 1892, concrete should be reinforced with a grid pattern of steel rods. The steel gives the concrete the added strength it needs. You will notice the steel is laid out with consistent spacing and is tied together where the the steel sections overlap and intersect. The thickness of the concrete, the thickness and spacing of the steel are determined by the intended use of the concrete and the forces it is expected to endure. In our case steel the concrete was at least 4″ thick with 3/8″ steel laid on 12″ centers in both directions. Additional reinforcing was “doweled” into the existing deck and pool beam, meaning we drilled into this existing concrete and installed steel which is tied to our new deck sections. This doweling will keep the decks from drifting apart over time. But it is important to note that where two sections of concrete meet, an isolation joint will be created. An isolation joint creates a small, but necessary space, usually filled with a flexible mastic material. It separates the two sections allowing for small minute movements in the concrete, caused by the expansion and contraction of concrete. If isolation joints are non-existent or incorrectly installed the concrete will not be allowed to expand properly and can crack or cause neighboring sections to crack.
Adding Decorative Pattern to Deck
You may have noticed from the photographs that the existing deck is cantilevered over the edge of the pool. Many pools have brick or stone that sits directly upon the beam, or walls of the pool, and is commonly referred to as “coping”. The decking is laid up against this coping. However in a cantilevered style deck there is no coping, instead the deck is laid up to and across the top of the pool beam. The look is very clean in appearance as there is no additional visual transition between the deck and the water. However, experience has taught us that in the north Texas area this type of deck, combined with the expansive nature of our soil is problematic. The movement of the decks is so extreme it commonly causes tile around the pool’s edge to become displaced. Many builders will no longer install cantilever decks for this very reason. In our case, we wanted the clean look of the cantilever, but decided to construct the deck in two sections to alleviate the problems with traditional cantilever decks. We poured the “coping” section first. It was patterned the same as the rest of the deck, which disguises our isolation joint. The rest of the deck was poured the next day. Extra effort was takent to make sure the patterns in our decorative concrete aligned across these two sections.
Applying Color and Pattern to the Coping Section
Adding a decorative pattern to concrete involves applying both a pattern to the concrete as well as a color. The pattern is applied to the concrete after it has been poured and begun to harden, but before the concrete is no longer malleable. The timing is critical and requires experience to get it right. In our case, since we poured the deck in two section, at two different times, the pattern had to be applied twice, once to each section. The most detail was applied to the front face of the coping section, since this area presented itself first to someone walking into the are. This section required additional forming, made out of styrofoam in order to achieve the consistent rounded edges we desired. In the photo you can see that once the styrofoam form was removed, a top coat was applied to the concrete that had been hidden by the form, in order to apply the pattern and coloring to this section. It is detailed work, but the finished product is worth the effort.
Applying Pattern to the Concrete
The second section, being much larger than the coping section, required more effort to apply the pattern. One of the secrets to good decorative concrete, is to have a number of patterns. If too few of these “stamps” are available, the eye begins to pick out the repetitions in the pattern and the project risks calling too much attention to itself. Another secret is the artistic experience of those who apply the pattern. In our case since we were using an ashlar pattern, which is made up of different combinations in size and shape, smaller and larger, rectangles and squares. It takes skill to combine these shapes, covering the area required, but using visually pleasing combinations. Although color has been added to the concrete mix an additional “release” color is added, after the patterns have been applied. This release color will give added visual depth to our project.
Finished Deck with Color Highlights and Sealant
After a curing period, approximately 2 weeks, the final color highlights are applied to the deck. These highlights are what allows the deck to take on a more natural appearance. No decorative concrete will look “exactly” like natural stone, but with a skilled applicator it can take on an amazing appearance, which will rival natural stone, given concretes easy of installation and maintenance. You may have noticed that as we neared completion some darker blue stone colors were added to match the few blue bricks of the house. A mastic joint was added between the coping and deck sections. This rubberized mastic was topped with a “decorative” or colored sand to allow it to blend into the deck. Finally a concrete sealant was applied to protect the concrete. This sealant will have to be re-applied every 2 to 3 years.
With the work complete, the clients can now enjoy a more usable social space, with a quality material, which is both visually pleasing and integrated into the setting. More importantly, access to this area is now easier. With no elevation changes, it will be hassle free, for all the family members to enjoy dinning and relaxing in their new pool area.
After the building permits have been issued, the utilities located and re-routed if necessary, the next step is the excavation process. This is one of the most important stages of your pool’s construction. You must realize that once a hole has been dug, any changes to the location , its shape or its size will likely cause an increase in the cost of the project. That is why most designers and builders go to extra measures to insure that the location, shape and size are clearly confirmed before the ground is broken. Even though I present plans and perspective drawings, which give good ideas of the pool’s future appearance, most people can not visualize completely what the pool will eventually look like. I find it helpful to “paint” the pools outline in the grass, before the excavator has even arrived. This paint, far from permanent, helps most people see the pool in its proper context, before any digging begins, which is far more permanent. With the paint marks, most people will get a better feel for the pool’s size and orientation. It is here you should be asking questions, such as but not limited too the following:
Will you be able to see the pool from inside as you want?
How will I move from the house to the pool?
Where is the pathway to be located?
Is there enough room to move around the pool?
Is there enough room to lounge on the deck or in the pool’s lounging area?
Will the sun light strick the lounging area as you want?
Is there enough shade where you want?
Will the children be able to play as you intend?
Is there enough room to entertain as you envision?
At this point changes can be addressed rather easily. The skill of the designer will also pay off here, as he should have been able to anticipate most of your question.
Heavy Equipment
Once everyone is pleased with the layout, the digging can begin. Where possible a full size excavator can be used to remove any unwanted objects and dig the pool to its proper depth. You should be aware that the equipment needed to build your new pool, particularly the excavator, can be quite large and make quite a bit of noise. The equipment and personnel need to run it will take up space, inconvenience your neighbors and destroy landscaping between the staging area and the location of your new pool, including fences and other objects in the path of the equipment, which, in the case of the excavator, needs at least an 11 pathway for clearance. Trees and shrubs in the area which are to remain should be protected. This protections should extend to the “drip line” of tree. Many think if the tree trunk is protected the tree will survive. This is not necessarily the case. As large equipment moves acrossthe roots of trees, the soil can become compacted making it difficult or impossible for the tree to survive the stress. Talk with your designer and builder, or even to an arborist, as to what measures are necessary. It should also be part of the planning process to also repair the grasses, landscape, pathways, irrigation lines and fences that will be unavoidably damaged.
Debris Removal is Quick with an Excavator
Care must be taken to reduce traffic problems and inconveniencing of those who live around you. Many cities have limitation on working hours, mandating most work to begin after 7 am. Fortunately most of the better pool contractors understand the inconvenience the experience can cause and do their best to limit the disruptions where possible. The largest piece of equipment used on the average pool is known as the full size excavator. It is an impressive piece of equipment and can remove the dirt for most pools in the space of a few hours. Hard or rocky soil can lengthen the process, particularly if access is limited and the builder is required to use smaller digging equipment. Rocky soil can also increase the cost of the excavation. Many pool builders build into their project cost certain allowances for the excavation portion of the pool. “Overages” beyond the anticipated cost will likely be charged to the owner. This is why, among other things, my recommendation, as written in “It Begins with Design”, is that a soil’s analysis be performed to determine the type of soil and the suitbility of the soil where the pool is located, prior to the excavation process. These reports should indicate not only the presence of rocky soil, but also if extra measures are required to support your pool If a soils report was not undertaken, as a minimum, having a soil engineer observe the soil conditions once the pool is excavated, should at least be accomplished. This is rather cheap insurance to make sure the proper structural requirements necessary to preserve the pool, in its present location.
Digging the Pool
Once the pool excavators are finished, you should be able to see the most prominent features of your pool. The actual pool will be slightly smaller and shallower because you must allow for the thickness of pool structure. Walls separating the spa from the pool and steps, in most cases, will be formed completely out of reinforced concrete, and may not be visible at the point. However you should be able to notice benches and lounging areas and the general location of the spa. In some areas of the country, particularly in coastal areas, where the water table is high, the pool has to be completely “over excavated” because the hole will not retain its shape, collapsing in upon itself. Where the soil holds its shape, forming boards will be placed above grade and in special areas to allow the concrete to be “shot” against it. (More on this subject later.) But in the areas where the walls collapse, the over excavation allows for the walls to be formed out of wood, where the concrete will be eventually attached.
Once the excavation equipment leaves the yard, the hole is typically exposed, since fencing material has usually been set aside to allow access. Generally laws dictate some form of temporary fencing surrounding the newly formed hole to prevent accidents. However the first major step, and typically the most dramatic, has been completed.
