How to waterproof a habitable basement
You will need to provide a Grade 3 Habitable basement to comply with BS8102
You need a 20 year guarantee. The only meaningful guarantees are Products Insurance backed guarantees.
To comply with British Standard’s you should have 2 forms of waterproofing.
From a design point of view. Type C is mandatory to comply with BS 8102 2009 and for common sense reasons. If the waterproofing leaks for any reason you have to be able to resolve the problem with the minimum of disruption to the occupier. You cannot do this with A or B systems.
Type A is an external sheet membrane or coating system which forms a barrier.
Type B is an integrally waterproof structure.
You cannot expect Type A to be installed completely defect free (this is a precedence set in law Outwing Case )
Why is waterproof concrete so problematic?
Type B basement construction is notorious for leaking. This cannot be disputed by suppliers as the evidence is over whelming. MacLennan-LSE work for waterproof additive companies, repairing failures with our injection systems and cavity membranes. All of the waterproof additive companies have to employ injection specialists to put right their frequent failures.
Additives do not stop leaks through cracks, honeycombing and joins. The additional reinforcement and joins required by most additive companies add unnecessary cost to the construction.
The additional reinforcement as required by waterproof additive companies is expensive and causes problems for detailing and pokering effectively.
If you have a leak after construction phase the additive companies will not return until fixtures and fittings and even internal walls are removed at the clients’ expense. They will not accept consequential damages.
To inspect or prove a failure with Type A the property needs to be excavated and this leads to more damage.
Type A and waterproof additives should not be used together as type A protection will prevent Autogenous healing if the type A is installed soon after construction.
All of this has to be considered during design and liability does fall on the designer if it is not.
A concrete structure without waterproof additives but with well compacted concrete and no honeycombing and well prepared (scabbled) joins with water bars will provide a Type B structure.
A concrete structure with additives and reinforcement to BS8007 but with less than adequate workmanship in any small area will leak. Honey combing occurs due to lack of accessibility to poker due to the amount of steel. Water bars are difficult to detail and install. surface prep of joins is difficult due to steel.
MacLennan-LSE Design
We install internal and external waterproofing.
We would always recommend an external system to protect concrete reduce damp ingress and to provide a dry environment in which the Type C system is a standby system which is installed for peace of mind.
The Type C system has the guarantees and full compliance with British Standards by being a serviceable system.
We cannot guarantee an external system on its own. Guarantees for external systems are not worth anything to the client. Contractors and suppliers will always find reasons for not honouring guarantees.
Product insurance and insurance backed guarantees are not available for external Type A systems. If you are offered one please talk to us and we will demonstrate why it will not give you protection.
We can install several different external systems. Some pre applied onto piles or formwork before concrete is poured. Others are membranes adhered to the finished concrete. We also spray cement based systems and crystalline penetration systems which are partly Type A barrier and Type B structure as they waterproof the concrete.
We can guarantee an internal type C system for 20 years as a standalone system if the concrete is BS8110. The joins need to be well designed and installed and the client has to have a maintenance agreement for sumps and pumps.
Designing this from drawings is a simple matter for us and is easily refined by mail or phone.
We design as many as 600 basements a year from drawings.
We are always happy to attend design finalisation meetings once we have some sort of commitment from the client that we will either win the work or a good percentage of the work we are involved with from this client.
Where we have a track record of winning work with an architect or engineering practice we will if required attend design meetings but normally find that we could have given the same advice and input from our desk by Mail , phone or conference call and saved a day out.
What you should insist on if you are looking for a waterproofing company
- Design, supply and install waterproofing systems. No split responsibility
- Take full responsibility for waterproofing Basement walls, floor and roof
- Accept design liability on our PI (unlike any manufacturer).
- Give insurance backed guarantees of up to 20 years
- Provide an insurance backed products guarantee for consequential damages (this is critical as it covers consequential loss.)
- The above is not to be confused with Insurance backed or bonded guarantees or Manufacturers guarantees none of which protect the client to the same degree or offer consequential damage cover.
- Ensure compliance with all relevant standards.
- Show evidence and references for a large number of similar installations. We can show hundreds
- Comply with all relevant health and safety requirements.
- Do not use sub- contractors for specialist work. Only own fully trained staff
- Can prove to be trusted and endorsed by some of the foremost market-leading architects, engineers and building contractors.
- Agree to accommodate project time constraints
- Are very competitive on price taking all of this into account.
Maclennan-LSE does all of the above and takes the worry out of all the financial risks associated with structural waterproofing, protecting contractors, designers and clients with our expert design, supply and installation of the most reliable systems. We also provide the added assurance for clients knowing that we are covered by the most comprehensive and specialist insurances available.
