This will vary due to local by-law requirements, but typically will us 3/8″ to 3/4″ (10mm to 20mm) deformed steel bars at 8″ to 10″ centers (200mm to 250mm) in a square grid pattern. This is suspended away from the “boxing” (wood formers) by “stand-offs” a device 2″ to 3″ (50mm 60mm) long which keeps the reinforcing steel centered in the completed wall and way from the bottom of the (drainage material layered) excavation. After allowing for the pool recirculation system devices to be allowed for in the finished wall and floor, the entire interior is pneumatically sprayed with a slurry of cement, pool gravel mix, and water. What distinguishes the name “Gunite” is that the mix is delivered pneumatically down a 4″ (100mm) hose as a dry mix under pressure, terminating at the “spray head” or nozzle where water is added by the operator. This is a vital part of the procedure, as the ingredients must be mixed in a critical percentage, or the resulting concrete will lack strength. For this reason, Gunite pool walls are usually thicker than other methods which will be addressed in this article. The consistency of the mix is measured in “slump” i.e. an upturned “witches hat” of the mix is allowed to “slump” as a measure of how it will “stick” to the vertical Re bars. 4″ (100mm) slump is common in these pools. Once the concrete has been placed into the pool, the interior is “straightened” by a team of operatives who use steel formers and trowels (“Floats”) to straighten the interior walls. (The exterior walls are held in shape by the “boxing”). Particular attention is taken to the top 12″ (300mm)of the pool as this is typically where a row of Mosaic Tiles will be fitted in the final phases of the pool construction, but the majority of the interior is left in a relatively rough state as it assists the adherence of the final interior plaster finish.