A pool base refers to the concrete floor of a swimming pool. In Perth, many in-ground swimming pools are constructed from concrete (as opposed to fibreglass or vinyl-liner pools). For a concrete pool, the shell is comprised of the base (floor) and the walls, all of which are typically made of reinforced concrete, either cast in place or shotcreted (sprayed concrete). The pool base is crucial because it not only must support the weight of the water above it but also tie into the walls to form a watertight vessel. Constructing a concrete pool base involves creating a smoothly contoured slab that often slopes (deeper at the deep end), with substantial reinforcement and precise attention to waterproofing.
Key points about concrete pool bases:
Pool floors are generally quite thick relative to normal slabs, often on the order of 150 mm (6 inches) or more, depending on pool size and engineering requirements. In some designs, the floor can thicken towards the deep end or where it meets the walls for added strength. The entire pool shell is reinforced with a network of steel bars (rebar) in both directions on the base and similarly up the walls. For example, one might see Y12 rebar at 200 mm spacing each way in the floor, with extra steel around penetrations (like the main drain). The reinforcement ensures the pool can handle the bending stresses between the span of the floor and helps control any cracking. Engineering is critical: the pool base is designed to handle the pressure of the water inside and also any external pressures (like groundwater or earth loads when the pool is empty).
Often, the base and walls of a concrete pool are formed as a single monolithic structure (especially in shotcrete construction) to eliminate cold joints and enhance water-tightness. If the base is poured first and walls later (cast separately), the construction joint is carefully treated with waterstops or epoxy to prevent leaks. A monolithic approach with shotcrete will have the floor shotcreted and then immediately the walls, or a continuous pour for formed concrete, which creates a stronger shell. Either way, the base-to-wall junction usually has extra reinforcement (like bent bars or a curb) because that corner endures high stress and is a common place for leaks if not well constructed.
The pool base is usually contoured (a shallow end floor slope transitioning to a hopper in the deep end). It needs to be accurately shaped as per the design depth profile. After the structural concrete is in place and cured, the interior of a concrete pool typically receives a finishing layer such as plaster (marble sheen), tiles, or a render with waterproof additives. The structural concrete itself is dense and can be made waterproof (with admixtures), but the final waterproofing often relies on the finish layer. Nonetheless, the concrete base must have no honeycombing or major cracks to ensure durability under the finish. Many concrete pools also include a waterproof membrane or crystalline waterproofing applied to the shell to seal any micro-cracks. Additionally, all plumbing penetrations (main drains in the floor) are securely embedded and sealed in the concrete to avoid leaks.
From a construction standpoint, building a concrete pool shell in Perth involves excavation of the hole, placement of formwork or shotcrete guides, fixing a cage of reinforcement covering the floor and walls, and then spraying or pouring concrete. The base is typically poured first in a conventional method, while in shotcrete, everything is done in one process. After curing, the shell is cleaned, any minor imperfections are patched, and then the interior finish is applied.
A properly built concrete pool base and shell is extremely robust; it is essentially a thick, tank-like structure. It can easily last for many decades, holding water without issues, provided the concrete mix is correct (often a high-strength mix, e.g., 32 MPa, with low permeability) and it’s been cured well. The pool base also resists hydrostatic uplift (if groundwater is present, the weight of the concrete and water usually counteracts it; sometimes hydrostatic relief valves are installed in the base for safety if the pool is emptied).
In summary, the pool base is the foundation of a concrete swimming pool, and in Perth’s climate (with no freezing temperatures but plenty of ground movement potential in clay zones), it’s vital that it’s built with care. When done right, a concrete pool base provides a solid, leak-free bottom for a beautiful in-ground pool, allowing Perth homeowners to enjoy their pools year after year with confidence in the structure beneath them.
