Basement waterproofing is often deemed as risky. This should not be the case. If basement waterproofing is carried out to a design following some very basic principles it will never fail. The design principles have been fudged in most codes of practice and standards, to accommodate the requirements of all the different manufacturers and suppliers. Contributors are often more worried about their sales and liabilities than they are about a completely robust waterproofing system with no risk.
The Design team must include a waterproofing expert.
This is a requirement of BS8102. The designer should be qualified and suitably experienced. Not a manufacturer. A manufacturer or supplier can only advise on and recommend their own products. The designer should be able to draw on all available products to provide the correct waterproofing solution.
The designer must take full liability for the waterproofing on there own PI, waterproofing must be from the DPC down.
A great many failures are as a result of surface water draining, and are not associated with the water table. So you should disregard any assertions that the water table is below the basement level and therefore the basement is low risk. The top of the basement is often the most vulnerable. You have to waterproof from the damp course down.
Form a watertight structure.
If you build out of block-work or insulated form work you are building a very high risk porous structure. It will be difficult to waterproof and if tested with water is likely to fail. We can supply guaranteed basement waterproofing for high risk construction but you will require a full external system and internal system and may need regular servicing.
Consider 2 Forms of Waterproofing.
If you build out of block work or ICF you must have 2 forms of waterproofing. You should have 2 forms if the risk of a leak is high or if the consequence of a leak is unacceptable. It is always unacceptable to have a leak accept in a car park with drains against the wall. Habitable, residential basements and storage should always include a cavity drain inside the basement.
Always consider reparability and servicing.
If you wrap a basement in waterproofing and then backfill, it how do you repair any defects. You cannot install external waterproofing defect free that is precedence set in law. You have to design with this in mind. How do you repair a basement built with watertight concrete and then completely lined internally with block or dry lining. You cant. You have to strip out the basement to find the leak. Leaks happen. Anyone who tells you the structure wont leak has not been involved with a lot of basements or they are not being completely honest with you. All of the big manufacturers and suppliers have leaks in their basement. You have to put a system inside that can be serviced or if necessary repaired with minimal disruption to the occupiers. This needs to be designed by specialists to minimise the risks of waterproofing.
The designer of the basement waterproofing must have PI specifically to cover the design of waterproofing Insist on Products insurance. This is the insurance that cover all eventualities in the event of a problem with the waterproofing If you don’t have products insurance then the guarantees are of little value. most guarantees are not covered by insurance.
Always ensure the waterproofing specialist has a long trading history, financial stability and experience with hundreds of similar constructions to the one you are proposing.
Anything less than due diligence is putting your project and client at risk.
None of this advice should be controversial it is just plain common sense.
Any design not following these rules is inadequate and puts clients, contractors and designers at risk of financial loss and possibly major disruption and unacceptable stress.
All of this can be avoided let us help, call for advice and design for your project.
Call at the beginning of the project, let us get the design right from the beginning.Click here for more information on our basement waterproofing services.
– Ian MacLennan