Concrete pavers around pools

Pools require much excavation and soil backfill against them. This soil is almost impossible to compact adequately because there is a high risk of compaction equipment damaging the pool wall, the metal “knee” wall/wing wall supports used in fiberglass pools, and/or pipes.

Pools made with gunite concrete or poured concrete can have walls of sufficient thickness and support where backfill soil against them can be compacted. However, the soil directly against the wall will be difficult to compact, again because of the risk of damage to a plate compactor or to the pool wall.

Therefore, settlement can occur at the wall as well. Some paver installation contractors claim that installing and compacting the soil backfill and aggregate base can reduce the risk of settlement. That may be true assuming that maximum density is achieved for both materials during compaction. However, the places compaction equipment cannot reach will be at risk of settlement and a customer call back. To avoid this, use a 4 in. (100 mm) thick concrete pad as a base. Placing a 2 in. (50 mm) thick layer of free-draining compacted aggregate such as ASTM No. 57 stone under the concrete base enables water to drain from below. The concrete base surface should slope at least 1.5 percent to allow water to drain.

A key aspect of all pool surfaces is no settlement or undulations that present walking or tripping hazards, or slipping hazards from birdbaths. By providing a rigid, sloped foundation, a concrete deck under the concrete pavers helps maintain safety. This should be the first priority and result of all paver pool projects.

An apron or the full dress? When a concrete base is used, it shouldn’t be an apron covering only areas of settlement-prone compacted soil and aggregate base around the pool perimeter. It needs to extend as a full dress under the entire area of the concrete. The problem with apron construction is differential settlement of the soil and base next to the concrete base under the concrete pavers. Settlement will almost always occur regardless of diligent soil and base compaction.

Sealing the surface and joints is key to holding jointing sand in place. Pavers should be sealed with a liquid sealer that also stabilizes the jointing sand. The sealer keeps the sand in place while preventing stains from chlorine, bromine or salt, depending on the type of pool water. Also, the sealer helps prevent food stains and keeps the surface looking fresh with vibrant colors. For more technical resources, please see technical resources at www.icpi.org.

The author is technical director for the Interlock Concrete Paving Institute.