New Commercial Construction
What is Gunite?
National Pools of Roanoke, Inc. builds Gunite pools. Gunite is pneumatically applied concrete, which can achieve strengths of 5000 to 7000 PSI (cast in place concrete is usually 3000 to 4000 PSI). Gunite’s strength is the result of the dense packing of the material as it is sprayed, as well as the fact that a relatively small amount of water is required to hydrate the cement. Gunite has been used in the construction of swimming pools for well over 40 years. This includes Olympic competition pools and the swimming pool at the White House in Washington, DC. Gunite is uniquely desirable for pool construction because of its inherent strength as well as its adaptability to unusual shapes. Gunite is particularly useful on vertical surfaces such as pool walls where extra strength is important.
The Design Process
National Pools of Pools of Roanoke, Inc. designs swimming pools and spas using Computer Aided Design (CAD). Plans for all pools are drawn in-house, including a plan view dimension layout, plan view plumbing layout, side section view, typical wall section, and filter room layout. Our pools are designed to meet the International Pool and Spa Code.
The dimension layout includes the overall dimensions of the pool/spa, as well as, the dimensions and locations of plumbing fittings within the pool. This layout will also include the placement of steps, seats, lights and any other features of the pool. The plumbing layout shows the routes of all piping to be installed in the pool and the size of each line. This view is also shown with the filter layout as a site plan to determine the location of the plumbing ditch. This layout is very important in case a pipe needs future repair and needs to be located.
Section view shows the pool depths and cross section of the pool shell. In this view you can see the slope of the floor and height of the walls at the center-line of the pool. The typical wall section displays the materials included in the pool construction. This section shows the sub-base, thickness of the pool wall & pool floor, strength of the concrete & gunite, size of the steel rebar, thickness & color of the plaster, size & color of the waterline tile, size & color of the coping, expansion joint and decking material.
The filter layout shows all the equipment used for water circulation and filtration. This layout displays the dimensions of the equipment room or slab, as well as, the size & type of pool/spa pump and filter, electrical panel, floor drain(s), and backwash line. Other items that may be seen in this layout (if desired) include the size & type of pool heater, chlorinator, automation controllers, and etc. The Area, Perimeter, Volume, Turnover Rate, and Flow Rate of the Pool are given on the plans. Also, the electrical/mechanical requirements, as well as, any work to be done by others are shown.
Codes are increasingly being updated and requiring additional engineering. If required, our plans can and have been engineered stamped to meet requirements set by the building departments. All our drawings are kept on file for ease of reference, as well as, to obtain information requested by the owner if any construction related specifications were needed in the future.
The Construction Process
The first step in constructing your new pool is the pool layout. Using CAD drawings built in-house and a transit, the pool location is laid out by setting batter boards and radius points. Strings and paint are used to outline the perimeter of the pool to match the design you’ve chosen.
Excavation can then begin. Using a trachoe and bobcat the pool depths are carved into the soil. The pool is over dug to allow for the pool shell to be constructed. The excavated soil can be used as backfill onsite or hauled off.
The pool can now be formed. Wooden forms make up the perimeter of the pool, as well as, any sections of the pool built out of the ground. The dirt and perimeter forming serve as the forms for concrete placement.
The crushed stone sub-base is then prepared, and the pool piping is ready to be installed. The sub-base includes 6” of #57 stone to keep the pool shell from settlement. As the stone is being leveled, the piping is installed simultaneously.
The pool is plumbed with high-grade NSF (National Sanitation Foundation) approved “Schedule 40” PVC pipe, fittings and equipment. These make up the circulation system to your skimmers, main drains, returns, spa jets, waterfalls, and/or to any other special items that you’ve chosen to customize your pool. All pipe connections are solidly and permanently bonded with PVC cement. Then, the entire plumbing system is pressure tested to 10 psi to make sure there are no leaks. All plumbing work is performed by our in-house team of experts who have been plumbing our pools for more than 30 years.
Next, a steel-reinforcing grid is installed to give your pool superior strength. A No.4 Bar 12” O.C.E.W is used to reinforce the concrete/Gunite. Also, walls where water depths are greater than 5′ receive additional vertical reinforcement. Cinder bricks are used to jack up the steel grid from the sub-base for adequate concrete cover. This makes for the strongest possible shell for your pool. It’s amazing to watch our crews in action as they bend and shape this steel with skill and experience that reflects many years of performing this job.
The 6” pool floor is placed using 3500 psi ready mixed concrete. The concrete is pumped or brought in off the truck depending on access. The concrete is then placed and hand troweled or floated to the desired elevation. The walls, as well as any steps or bench seats, are then constructed using Gunite.
Now comes the unique process of “shooting the Gunite” to form the hard concrete shell of your pool. Gunite is a mixture of sand and cement that is applied by an experienced team of craftsmen using specialized tools and a Gunite Rig. The sand and cement are mixed dry on-site using a Gunite rig and pumped pneumatically by hose where it is met with water at the nozzle. Our certified nozzlemen will skillfully shoot 6”+ of Gunite around your pool’s steel reinforcement grid to form your pool wall. This combination of Gunite/Concrete and steel reinforcement produces an extremely strong and durable pool shell. The Gunite walls can test up to 4000+ psi. The ability to customize your pool or build your pool to any shape, size, or depth desired is the advantage of a Gunite pool.
Tile & Coping
The next step in the construction process is the installation of a six-inch wide band of waterline pool tile at the perimeter. This tile is hand-laid and carefully grouted by our skilled craftsmen. It’s critically important that highly experienced craftsmen handle the tile work. Since water is naturally level, any errors in the straightness or elevation of the tile will be instantly visible. Coping is then installed if chosen. Coping is the stone laid on the pool beam and can be of pre-cast concrete, brick, stone, or cantilever decking. National Pools offers a variety of colors in pre-cast concrete coping and brick. Other materials may be installed by the decking contractor.
While the work surrounding the pool is being done, the filter system will be installed. The pump, filter, and heater (if desired) will be sized and installed according to the filtration/flow requirements.
Deck, Fencing & Utilities (Done by Others)
The decking around your pool is done after the coping is placed. The pool shell will have a sidewalk support for the decking to set on. An expansion joint will be installed between the coping and deck, however it must be caulked by others. The fencing around your pool is done at this time. The pool equipment (pump, heater, controllers, etc.) must be wired by a certified electrician. Also, if your pool or spa package includes a gas heater, then a mechanical contractor must be used for gas connection. National Pools can assist in recommending a qualified contractor for these steps, but due to legal requirements, a certified contractor must handle the natural gas/propane plumbing and electrical connections. The electrical and mechanical work can happen concurrently with other construction phases, so it need not hold up the construction process.
Now – the final step. After all the surrounding work is complete, the pool walls and floor are finished with a ¼” to ½” thick layer of either Marblite or Exposed aggregate plaster in typically white, grey or black finishes. This surface must be cared for very closely in the beginning stages after pool completion as the plaster cures. Water chemistry must be maintained and the surface must be brushed frequently to prevent discoloration and reduce mottling. A properly cared for plaster finish does not require painting and can last for many years. When the plaster crew finishes this process, your pool is complete! Just add water. It’s time to swim!