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Specialist basement contractor whose work has never leaked.

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Whether small
or large

New-Build Waterproof Basement Construction. We do not go under anything already there.

Many of our clients buy something small, we build their basement, then their builder builds their house on top.

basement expert

We can be your main contractor, your sub contractor or work with you Value Engineering.

Value Engineering produces the biggest savings and often the best results but the work is not for a fixed price. We can agree incentives so that you don't pay more than you expect.

Being your contractor, having agreed a written contract, makes the work subject to the Construction Act. Do you understand the Act fully? By law, all construction contracts fall under the Act and its arrangement for resolving disputes. Many would say it does far more harm than good, being "incapable of delivering for its clients".

We have a page explaining the pitfalls and how we like to avoid them here.

A recent project was in Esher, where we began as a sub contractor to a main contractor, but half way through the client parked the other contractor and we were the main contractor until the basement structure was complete.

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It is the details that matter. Ledges for brickwork below ground yet the waterproof concrete continues above ground.
This has been a very tight site. We have had to build in many small stages.

waterproof concrete basement and pool

Protecting the public highway from collapse has been a priority.

At the beginning of October the project manager for the works provided us with this reference.

"To whom it may concern.
We have been working with Basement Expert Ltd and Phil Sacre on a rather tricky basement job in Esher where the retaining wall was on the pavement line. Phil was ever present on the job and handled the difficulties professionally and effectively throughout. Despite payments upfront we never felt that he was taking advantage of us rather he just got on with the job. His technical expertise is second to none and we always felt we were getting the best possible solutions to the issues we encountered.
We have no hesitation in recommending Basement Expert Ltd and Phil Sacre and we will most certainly be using them again.
Please feel free to contact the undersigned for further information."

Obviously we cannot inundate this person with unsolicited messages from every prospective enquirer, but his details are available for any prospective customer close to choosing his or her contractor.

We complete all our work to BS 8102.
BS 8102 is the Code of practice for protection of below ground structures against water from the ground.

The code requires two defences against ingress of water
and that the first defence substantially reduces the amount of water dealt with by the second.

The first defence we install is always waterproof concrete, with all the work carried out properly. The concrete all but completely prevents water ingress. We guarantee no visible leak of water no matter what your ground conditions. More information here.

We prove to BS EN 12390-8:2009 that the concrete we used in your project is completely impermeable.

And we personally guarantee against visible leaks of water for 12 years.

The other defence will often be internal or external drainage. Your insurer, if you have one, will make this choice. Otherwise it will be the choice of your architect.

If we install your external drainage we will do it properly to the approval of all concerned.

We will leave a large sump in the base to enable internal drainage to be installed by a specialist contractor after the roof is on and the windows are in. There is no point in installing such drainage sooner since the basement is going to fill with rain water and a submerged membrane will probably get damaged.   basement sump

We look after everyone throughout the building process.
  1. A proper written agreement detailing the work included and the stage payments.

  2. A certificate to BS EN 12390-8:2009 proving that the concrete used on your project is completely impermeable to water.

  3. Personal guarantee that your basement will have no visible leaks for 12 years after we finish.

Every client has a different scope of works in mind.

We are specialist civil engineers, you can choose how much we do from this list.
  • The excavation, muckaway and backfill.

  • The complete structure below ground, waterproof, guaranteed.

  • Basement external drainage.

  • Internal walls throughout the basement.

  • Window wells, stair wells, sunken patios, waterproof roofs over the basement.

  • External or internal insulation.
We do not fit out a basement with electrics or plasterboard because you need the roof on and windows in first. Therefore your builder is best suited for the finishing works.

Call me, Phil Sacre:

01438 900303

07773 377087

Email me:

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I was the original innovator of several waterproof basement construction practices widely copied and some now the norm:
  1. The waterproof concrete basement upstand to stop a horizontal ingress of water from ground level.

  2. Waterproof concrete basement walls cast without the usual causes of leaks: kickers and leaving holes through the wall, while still stripping the formwork to inspect the concrete.

  3. Making the basement concrete actually waterproof; which means we start with waterproof concrete and we move it, we place it, we compact it and we cure it - properly.

  4. Controlling crack widths in waterproof concrete basement walls.

  5. Value engineering where both parties work together to find savings.

  6. Basements constructed completely waterproof from the concrete alone.

BS 8102:2009 says:

6.2.2 Combined protection
Consideration should be given to the use of combined protection (i.e. Type A and Type B, Type A and Type C or Type B and Type C) where in a single system:
a) the assessed risks are deemed to be high (see Clause 5);
b) the consequences of failure to achieve the required internal environment are too high; or
c) additional vapour checks are necessary for a system where unacceptable water vapour transmission can occur.

Although structures with Type B protection are designed to be water resistant, additional waterproofing systems may be applied internally or externally to control water vapour movement, where appropriate.

An in-situ “liner” wall designed to provide Type B protection can be cast inside an embedded retaining wall to provide combined protection. In some cases, a fully bonded barrier might also be provided between the two elements.

Although structures with Type C protection are designed to control and manage seepage into a structure, where this is unacceptably high the water resistance of the structure should be improved prior to the installation of the Type C protection, by the application of either Type A or Type B protection.

When combining types of protection, the compatibility of the different protection types should be assessed in order to minimize the risks and negate the need for remedial measures.

In our opinion, Type A should only be considered where water will always drain freely by gravity alone.

But 'Always drains freely' is rare, which is why internal drainage is far more common.

We have a number of other pages with information.

waterproof basement construction   You Must Have a Soil Report Before Design Starts   Please Ask Your Architect To Read This Page   Please Ask Your Structural Engineer To Read This Page   construction contract

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The Basement Expert is Phil Sacre.

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