Posts Tagged ‘Pool Decks’

Shooting the Pool

Thursday, October 8th, 2009

By Tim Long

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

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

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

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

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

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!

To view a video of a pool shoot:

To read the previous article in this series, click here: “Initial Pool Plumbing & Electrical Work”

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Where Materials Meet

Saturday, June 6th, 2009

By Tim Long

Brick Coping with Reveal

Brick Coping with Reveal

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

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

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

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!

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Traveling Decks

Tuesday, May 12th, 2009

By Tim Long

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

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

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

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. 

Stress Cracks

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.

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Steel Reinforcement, It’s the Pool’s Skeleton!

Sunday, March 29th, 2009

By Tim Long

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

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.

Pnuematic Concrete

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

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:

  1. 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.
    2. Bending Steel to the Pool's Shape

    Bending Steel to the Pool's Shape

  2. 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.
    3. A Double Curtain of Steel for the Spa

    A Double Curtain of Steel for the Spa

  3. 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.
  4. 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.

Read the previous article in the series “City Permits & Utilities”.

To read the next article in this series, click here: Initial Pool Plumbing & Electrial Work!

To see a short video of steel being laid and tied, click here:

 

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Disguising Details

Thursday, March 26th, 2009

By Tim Long

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

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

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:

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Access for All!

Thursday, March 26th, 2009
Original "Raised" Wooden Deck

Original "Raised" Wooden Deck

By Tim Long

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

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

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

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

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

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

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

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.

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