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.
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.
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.
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.
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.
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.
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.
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.