Concrete Slab Requirements for Pools

Concrete Slabs

• A concrete slab that slab must be able to withstand the pool's weight. Standard concrete slabs run from 4 inches up to 8 inches thick, which is more than enough to withstand a pool's weight in most cases.Concrete has to have enough compressive strength to support a swimming pool but even slabs made of low strength concrete have enough compressive strength for the task.

Compressive Strength

• Compressive strength is a measure of how much weight the concrete can withstand if the weight's placed directly on top of it. Conventional concrete can withstand compressive stresses of 7,000 lbs. per square inch (psi). Even low strength, or "3,000-lb. concrete," can withstand 3,000 psi. A standard 18-foot round, 4-foot deep swimming pool's water weight is about 63,700 lbs.(7,650 gallons x 8.33 lbs.), which even 3,000-lb. concrete's compressive strength can easily handle.

Slab Issues

• Before you place a swimming pool on a concrete slab always make sure it's level. A concrete slab that's not level will create a swimming pool that's not level. Water in a pool on a surface that isn't level will press against pool walls that aren't level, causing pool wall collapse. Additionally, don't place a pool on an above ground pool that's cracked or buckled because it won't be strong enough to support the pool's weight.

Considerations

• Concrete slabs can be somewhat abrasive and wear away a swimming pool's vinyl liner floor if slab surfaces aren't cushioned. Plus, a concrete slab's surface is just too hard for swimmer comfort, so cushioning the slab before a pool is placed on it is wise. Several good pool floor cushioning materials exist, including solid foam insulation and thick smooth carpet padding. Also, there are commercially available pool floor pads available, with an 18-foot round model costing, at the time of publication, about $120.