How to Choose a Swimming Pool Contractor in London: 12 Questions to Ask Before You Sign

Published: 16 October 2026 | By The Swimming Pool Company

A swimming pool is one of the biggest investments you will make in your home, and most of what determines whether it lasts is hidden once the water goes in: the steel, the concrete, the waterproofing and the pipework. That makes choosing the right swimming pool contractor more important than choosing the tiles.

Here are the 12 questions we would ask any pool builder in London, including us, before signing a contract.

In this guide, we explain how to choose a swimming pool contractor in London, the 12 questions you should ask before you sign, the red flags to watch for, how to compare quotes like-for-like, and the legal protections every homeowner should understand.

Key Takeaways

• Specialist experience: Choose a contractor with a portfolio of completed reinforced concrete pools in London, not just general building work.

• Engineering: The pool shell should be designed by a qualified structural engineer, with calculations suited to your ground conditions.

• Insurance and guarantees: Ask for written evidence of public liability and contract works insurance, plus the terms of any structural guarantee.

• Transparent pricing: Insist on an itemised quotation with clear exclusions and provisional sums, so quotes can be compared like-for-like.

• Staged payments: Payments should be linked to completed construction milestones, not paid largely in advance.

• Aftercare: Confirm commissioning, handover training and ongoing servicing before work begins.

  
  

How many pools like mine have you built, and can I see them?

Ask for case studies of pools similar to yours in type, size and setting: a basement pool is a very different project from a garden pool. A good contractor will show you photos, explain what was difficult about each project and, where clients agree, put you in touch with past customers.

2. Who designs the structure?

A pool is a structure holding many tonnes of water. Ask who calculates the reinforcement and wall thicknesses, and whether a structural engineer is involved, especially for basements, sloping gardens or pools close to buildings and boundaries.

3. What construction method do you use, and why?

Reinforced concrete, blockwork with a liner, and prefabricated shells all exist, and each has trade-offs in cost, flexibility of shape and lifespan. A good contractor explains why their method suits your site rather than offering only what they always build.

4. How do you waterproof the pool, and do you pressure test it?

Ask exactly which waterproofing system is used and how it is applied. For basements, ask how the design meets BS 8102, the British Standard for protecting below-ground structures against water. Ask too whether the shell is pressure tested before tiling, and for how long.

5. What does your guarantee cover, and for how long?

Find out what is covered (structure, waterproofing, equipment, finishes), for how many years each, and what happens if the company stops trading. Equipment usually carries the manufacturer's warranty; the structural guarantee is the one that matters most.

6. Is your quote itemised, and what is excluded?

An itemised quote lets you compare contractors like for like. Check what is not included: spoil removal, electrical supply to the plant room, landscaping and paving, pool covers, planning fees and VAT are common gaps that make a cheap quote expensive later.

7. How are payments scheduled?

Stage payments tied to clear milestones (excavation complete, shell poured, pressure test passed, tiling complete) protect both sides. Be cautious of contractors asking for a large share of the price before any work has started.

8. Who handles planning, Building Regulations and party walls?

In London, many pools need planning permission or a Lawful Development Certificate, and basements usually need party wall agreements and a construction management plan. Ask who prepares and submits these, and whether the cost is in the quote.

9. How will you size the heating, filtration and ventilation?

Undersized plant is a common cause of cloudy water, high running costs and, indoors, condensation. Ask how the heat pump, filtration and (for indoor pools) dehumidification are sized for your pool and room, not just which brands are used.

10. Who will actually be on site?

Ask whether the company uses its own team or subcontractors for each stage, who manages the site day to day, and who your single point of contact is.

11. Are you a member of a recognised trade association?

Trade associations such as SPATA (the Swimming Pool and Allied Trades Association) set construction standards and a code of ethics for members, and inspect contractors' work before accepting them. Membership is not the only sign of a good builder, but it is a useful check.

12. What happens at handover and afterwards?

A good contractor commissions the pool, balances the water, shows you how to run the plant, and gives you manuals and warranties. Ask whether servicing and maintenance are available after handover.

Red flags to watch for

• A single-figure quote with no breakdown.

• No photos or visits to previous pools of a similar type.

• A large deposit before any work begins.

• Vague answers about waterproofing, structure or guarantees.

• Pressure to sign quickly, for example a "discount if you sign today".

• No clear contract setting out scope, timeline, payments and exclusions.

How we answer these questions

We have designed and built reinforced concrete pools across London and the South East since 2011. Here is how we answer the questions above:

• Experience: indoor, outdoor and basement pools from £95,000 garden pools to £300,000 basement projects, all shown in our case studies.

• Structure and method: steel-reinforced concrete shells, designed for each site, with structural engineers on basement and complex projects.

• Waterproofing: specialist multi-layer waterproofing on every pool, BS 8102 for basements, and a 72-hour pressure test before tiling.

• Guarantee: a 10-year structural guarantee on every pool we build.

• Quotes: fully itemised, so you can see and compare every line.

• One team: design, construction, plant and finishes managed by us from first meeting to handover.

  
  

Frequently asked questions

Should I use a specialist pool company or a general builder?

A specialist pool company understands structure, waterproofing, hydraulics, water treatment and plant sizing, which most general builders don't do every day. We explain the difference in more detail in our post on choosing a swimming pool company over a general contractor.

How many quotes should I get?

Two or three itemised quotes from specialist pool builders is usually enough to compare scope and price fairly.

Why do pool quotes vary so much?

Different construction methods, different specifications, and different exclusions. Compare quotes line by line rather than on the total.

When should I contact a pool contractor?

As early as possible. For a pool ready for summer, start talking to contractors in the autumn or winter before, as design, quotes and approvals all take time and diaries fill from January.

Talk to us about your pool

Send us photos and rough dimensions of your space, and we'll answer every one of these questions for your project, with an itemised quote. Call 0208 058 0871 or send us your project details.

Sources

• SPATA, the Swimming Pool and Allied Trades Association: spata.co.uk, membership standards and code of ethics (overview via PBC Today)

• British Standards Institution: BS 8102, Protection of below ground structures against water ingress

• Party Wall etc. Act 1996: GOV.UK guidance