Lagoon pool or conventional pool: what really changes

The shape is obvious at once. What is less obvious is that the works, the way you enter the water, the budget and the way the pool ages are not the same. On those four points, the lagoon pool clearly loses one: price.

1. The building technique is not the same

A rectangular pool can be poured between formwork panels or built from hollow blocks: straight lines, corners, standard formwork. A free form cannot. It is dug to the shape wanted and made watertight with an EPDM geomembrane, a flexible membrane that follows every curve, with a stone carpet finish (we set out how a lagoon pool stays watertight).

As with any pool, the points to watch are the connections around the parts that pass through the waterproofing: skimmers, inlets, lights, and the waterline.

2. You get into the water differently

The ladder or corner steps give way to a gently sloping submerged shallow area. It is not just a matter of looks: it changes who can use the pool. A child who can stand for three metres, an older person getting in with no rung to step over, someone who simply wants to sit in twenty centimetres of water in the shade.

The proportions are set case by case: water depth at the start of the shallow area, depth of the main pool, and an even slope between the two. See how the depths and slope of a submerged shallow area are designed.

3. Integration into the garden

A rectangle imposes itself on the site: you often have to level, create a platform, frame it with straight coping. A free form follows what is there — a slope, an established tree, an old wall. After two or three seasons, with planting along the edge, the boundary between garden and pool becomes blurred. That is the effect sought.

4. Cost, and this is the weak point

A lagoon pool costs more than a rectangular pool of the same area. The custom shape, the membrane to fit, a longer length of edging and the landscaped surroundings explain the gap. If budget is the deciding criterion and shape matters little, a well-built conventional pool is a perfectly reasonable choice, and we build those too. We set out what makes the price of a lagoon pool.

5. Maintenance: much the same, with two nuances

A lagoon pool does not call for fundamentally different maintenance. The items are the same: filtration, water balance, cleaning. Two nuances all the same.

First, a shallow submerged area heats up quickly in the sun, which speeds up disinfectant consumption in summer and calls for a little more attention to water balance. Second, a planted edge brings more leaves: a properly sized and well-placed skimmer absorbs that without difficulty, but it has to have been thought about at the design stage, and the filtration sized and set accordingly.

Also worth noting: standard cleaning robots are designed for even floors. On a free form with a shallow area, you have to choose a suitable model, or accept finishing off with a net.

So which one should you choose?

A conventional pool if you are after swimming length, a controlled budget and a geometry that suits a contemporary house. A lagoon pool if your site has relief or planting, if the use is more family than sport, and if you want a pool that looks as though it had always been there.

There remains a third option everyone considers: the polyester shell. It is quicker to install and cheaper, but the shape is the mould’s, with no bespoke submerged shallow area and no adaptation to the site. It is a legitimate trade-off — simply, it is not the same product.

In practice, this choice is rarely settled on paper. It is settled standing in the garden, looking at where the shade falls at 4 p.m. and where the digger will go through.