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Planning the Swimming Pool Paving for a UK Pool

This article is about installing paving flags around an in-ground swimming pool. From an aesthetic point of view the pool itself is a small area of water that reflects the colours of the overhead sky and the pool walls and floor. It is the paving and landscaping that makes or mars the appearance of a swimming pool and so it is worthwhile taking lots of care and trouble to get it right.

Pool Paving Design

So what is the most important thing about the design of paving around a new swimming pool? The obvious answer is that it needs to look good but that is the wrong answer! The right answer is that it needs to be structurally stable. If it is not it may look good for a few weeks but when it starts to settle – as so many do – the whole pool will look dilapidated and neglected. The old truism in all the building trades that the preparation is the most important part of the process is never truer then when applied to paving around a pool.

Pool Paving Support Structure

Not only is the support structure the most important part it is also normally the most costly. In practice most in-ground pools will have a gap up to 500 mm wide between the outside of the pool walls and the edge of the original excavation for the pool installation. The backfilling to this gap can crucially affect the stability of the pool walls but I will deal with this in another article.

The main issue from the pool paving viewpoint is that this gap is never backfilled with properly compacted soil for all kinds of reasons. So when it rains and this backfill settles there should be a structure in place that supports the paving – otherwise it will subside.

Kit Pools cannot support Pool Paving

With many kit pools, the pool walls are not strong enough to support the weight of the structure needed to span across this gap and so subsidence is inevitable. Because of this many pool builders do not recommend the installation of paving around their pools until at least two winters have passed after backfilling around the pool has been completed. But who wants to wait two years to get their pool looking good?

Heavy structures can support the Pool Paving

Heavy pool walls, like concrete block walls , can easily be designed to support reinforced concrete slabs that bridge across this gap. So the best bet is to build a pool with walls that can support reinforced concrete slabs that in turn support the paving slabs. These concrete slabs should be installed with a slope of about 1 in 50 away from the pool edge to ensure that rainwater drains away from the pool.

The Support Structure

If the original ground around the pool is high enough and hard enough 150mm thick concrete slabs reinforced by a high tensile mesh reinforcement should be installed. They should be supported at one end by the pool wall and at the other end by the ground around the pool that was not dug out so at they span across the gap between the back of the pool walls. Then subsidence is reduced to virtually zero.

Surround Levels

If the surrounding ground is to low or too soft the levels need to be built up to support the outer ends of the concrete slabs. This can be done with the pool excavation arisings in thin layers not exceeding 150mm in thickness. Ideally these layers should be leveled and tracked in with a digger weighing at least 2.75 tonnes and the upper levels immediately below the slabs should be compacted with a roller or compactor.

If the excavation arisings are unsuitable because of a high silt or clay content gravel or crushed rock fill may need to be brought in.

Concrete Block Piers

When the pool walls are not strong enough to support these reinforced concrete slabs they can be supported by concrete block piers that are installed at right angles to the pool wall and 2 metres apart. This adds a lot to the cost of the pool and is one of the reasons why kit pools are really a waste of money.

Paving Levels and Trip Hazards

Most pools will have concrete or re-constituted coping stones (margelles in France). The best practice is to ensure that the top surface of the surrounding paving flags are installed flush with the top of the coping stones so there is no step that can be a trip hazard.

Laying the Paving Flags

Most paving flag layers prefer to lay the paving flags on a bed of wet mortar that is about 50 mm thick. The paving flags should be at least 35 mm thick because thinner ones will break up under low temperature freezing conditions in Europe and the northern US. The top of the paving flags and the coping stones will be flush if the top of the reinforced concrete slabs is set 85mm below the top of the coping stone level.

Just remember that the paving around the pool will make or mar the appearance of the pool.

The cost of doing it properly should be less than 10% of the pool cost so there is no excuse if it is not done properly.

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