Guest Expert: How to Build an Indoor Pool That’s Not a Damp Disaster

Monday, November 20, 2017

Paul Whiteley is Managing Director at Brookforge, who were the designers and builders of the incredible pool in Wimbledon Villa, which is one of the largest underground pools in London. He’s been working in the swimming pool trade for over 25 years, and Brookforge just celebrated its 20th anniversary, so we thought there’s no one better to share how you can have a pool of your own.

A pool isn’t just a hole full of water 

My favourite projects are those where we’re brought in from day one so that we can work alongside the architects and engineers and have our designs fully integrated into the plans, with everything we need to construct a watertight, well ventilated and beautiful pool.

Fixing an incorrectly built pool can be very difficult, time consuming and expensive. Many people don’t understand the complexity of an indoor pool, and will ask a builder with no pool experience to build them one, which often turns out to be nothing more than a concrete box with little or no pipework.

Without specialist tanking or correctly designed climate control, the pool hall becomes a damp, smelly, thoroughly unpleasant environment. I’ve visited some horror story pools that are not only hazardous for the client’s health, but a hazard to the structural integrity of the building itself.

Fixing a botched pool and retrofitting all the required equipment is more expensive than what was initially spent, so it’s more cost-effective and safe to do it right the first time with qualified and experienced pool experts.

You need space for a plant room

A proper indoor pool needs equipment to circulate, filter, heat, disinfect the water and to ventilate, dehumidify, heat, expel stale air, introduce fresh air and sometimes cool the air. This all needs to go somewhere, which is why you need to allow space for an appropriately sized plant room.

Plant rooms range from four to ten metres depending on the size of the pool, which is enough space for all the pool equipment to be installed (along with other equipment used in the house in larger plant rooms) with comfortable access for control, maintenance and repair.

Unfortunately, clients will often present us with far less than this, right down to spaces no more than two to four metres squared, which end up with all the equipment stacked on top of each other with no space for an engineer to easily access it. Needless to say this increases installation costs.

Running costs are negligible if you have a pool cover

The retractable pool cover at Wimbledon Villa keeps the pool hall looking attractive while significantly reducing running costs.

The main reason people give for not wanting to install a pool in their home is that the running costs would be too high. Pools need to be heated and ventilated, which requires a lot of energy, but pools can be made far less demanding if you simply cover them when you’re not using them.

Some clients insist on not covering their pools so they can look at the water all the time, but if you only use a pool for an hour or so a day, leaving it exposed to evaporate and lose heat for 23 hours doesn’t make much sense – especially if it’s hidden away in a basement. Running costs for the pool can be around £3,000.00 per annum, for a coverered, well insulated pool.

Pool covers don’t require any extra work from you, either. The pool covers we install are electronically operated, letting you control them via remote, home automation or – if you’re concerned about child safety – by key.

At Wimbledon Villa, the pool cover retracts into a void hidden beneath the gym that overlooks the pool from the shallow end, where it’s covered with a fibreglass fake wall that’s tiled to match the rest of the pool, making it difficult to tell there’s a cover at all when it’s not in use.

Pool covers are much better looking than the sad, bright blue bubble cover that might come to mind. Wimbledon Villa’s folds out to create a smooth, foam filled, slatted surface that looks just as luxurious as every other material used in the house.

Basement pools aren’t much harder to build

Technically, a basement pool isn’t all that different from any other indoor pool. The main challenges are logistical, as we have to transport all the materials and equipment underground, which can be awkward, tiring work.

To make things easier, we build our pools from Quadlock insulated concrete forms (ICFs), which are sections of twin polystyrene blocks that connect together with unique ties to create the formwork that concrete is then poured into. When this dries, you have a concrete wall with very thermally efficient insulation already installed on both sides.

Left: The assembled ICFs, ready to be filled with concrete. Right: The finished pool. Click here to learn how this vast underground space was created.

Best of all, ICFs are light enough to be carried by hand, which makes them a godsend in hard to access basements. They require so little labour to transport that, at Wimbledon Villa, we only needed one morning to get all materials in place.

Once the concrete has been poured and set, we apply a three-coat sprayed, flexible waterproof membrane to form a tanking system. Basement pools need to be double-tanked, meaning that the basement is tanked then the pool too, to make sure that no groundwater can contaminate the pool water and no pool water can seep into the structure.

Get in touch if you have any questions

I’m always happy to share my advice on designing and building pools, so if you have any questions, feel free to get in touch at [email protected] or visit our website at