If you waterproof a basement with everything available, what makes each workforce use anything properly?

Waterproof Concrete With Site Supervision Ltd was formed to offer the best products and the best advice its director found during 11 years building more than 50 domestic basements.

The director, Phil Sacre says, “When a drawing specifies several specialist teams are to use watertight concrete, paint-on bitumen, clay carpet, sticky-back membrane, internal drainage with a sump and a pump etc., the unavoidable psychological thinking in each workforce is ‘I needn’t bother’, and the unavoidable commercial reaction of each company doing the work is ‘We can cut corners’.

I have proven to myself time after time, if the workforce believes they are providing the one and only defence against ingress of water they do a far better job because any blame later is sure to be aimed directly at them.

I learned years ago how to concrete properly and never have a leak and that is what makes my basement business so competitive.

Concrete is inherently water resistant. That means that despite water getting through by capillary action, decent concrete does not visibly leak.

Visible flows of water are only through dirt, cracks and voids caused by the workforce. Improving concreting workmanship reduces repair costs and the need for any other defence.

So if an architect is planning to include internal drainage, he will need a far bigger system if it is specified on the drawings issued to site than if it is omitted from tender and site drawings and only included on the drawings to building control.

If an effort is made to persuade the site personnel to do a better job, the internal drainage can be designed later to cope with the actual issues – some damp, rather than beforehand when it must be designed to cope with the worst possible situation – flooding.

A smaller system only has to deal with the vapour that gets through and a few drips, because decent concrete used properly, and possibly after a few leak repairs, is never going to let vast amounts of water through.

Phil says: “Nothing gets through any basement we built, or helped build, recently where my ways were adopted. The first necessity is supervision. Someone who gets dirt in a wall removed and an area missed by a vibrating poker returned to, as well as insisting that the concreting pipe is inserted into the wall and each pour is limited to what can be placed and compacted well, never full room height in only one day.

There is no second necessity if you have good supervision. But with the concrete mix designed accordingly, vapour escape can be prevented as well.

With supervision, fully waterproof concrete and good design, such as an upstand and enough steel so any cracks self heal, the basement structure is and will always be completely waterproof to the extent that when it is first dried inside after construction it will always remain dry.

As a rule we include a very small sump in the plant room. A depression big enough to scoop water into a bucket is the favourite choice. That way plumbing spills can be dealt with easily and, if internal drainage is installed, a 50mm deep depression is ample for the electronic water detectors and pumps available today if there is any residual problem after concreting properly. I

hasten to add that we have yet to leave a basement built our way needing any internal drainage.”

“Usually a basement retaining wall is designed to just below ground level so that house construction starts just out of sight after external landscaping.

Usually, therefore, water from the surface outside when it rains can get through beneath the house construction and over the basement retaining wall. I say ‘usually’ because sticky-back membrane over that join rarely sticks well everywhere, is easily torn and covered over and has a limited lifespan compared to the building.

Reinforced concrete walls are mostly formed with double sided formwork using steel threaded bar through plastic tubes. The steel rods are withdrawn for further use and the holes through the plastic tubes repaired. They can be repaired very well, but it is a tedious and thankless task on site so some invariably leak.

Our way is to use fibre reinforced plastic threaded bars that get cast in, no holes to repair, and to cast an upstand using the same waterproof concrete to support the main construction over to above outside ground level so that brickwork can start out of sight as usual and the cavity tray behind is monolithic with the basement.

Concrete is the first construction material used in basement construction. It can save a lot of money if it is waterproof both as a material and by design.

It takes a certain amount of determination, not money, to achieve fully waterproof from the concrete alone. It is not expensive, neither is it difficult because our amateur self builder customers who choose us and adopt the methodologies succeed time after time, often for half the best quote they got from contractors.

But seasoned professionals live in a construction world where poor workmanship is more competitive than good. They are commanded to do their work badly by bosses keen to remain in business.

The designer can easily make a difference by making it appear that the concreting contractor will, alone, be held responsible for all leaks – but specify good materials as well.”

Waterproof Concrete With Site Supervision supplies three products and services. 1. Supervision and/or training of the concreting team.

2. An additive that makes the right concrete mix completely waterproof, and samples of concrete used on each project are taken and proven to BS EN 12390-8-2009 to be completely impermeable. Some certificates are on the web site.

3. Fibre reinforced plastic threaded rods and nuts.

Waterproof Concrete

The concrete additive is called Triple Proof.
It is added to concrete at the rate of 500mls per cubic metre of concrete.

The concrete to order is:
Minimum cement content P350
Pure OPC CEM 1
Maximum water/cement ratio 0.45. All the water is required.
Over sanded for pumping
Target slump 40mm
Plasticiser will be added and mixed in by the pump operator on site. No other chemicals to be added by the batching plant.