Expert: Dan Griffin - 3/4/2008

Question
WHAT IS THE BEST WAY TO WATER PROOF THE EXTERIOR BASEMENT BLOCK WALLS (NEW CONSTRUCTION)?

Answer
Most basement walls are damp proofed.  It is more expensive and complicated to water proof a wall.  


Any drainage system begins under the footing, the footing keyway,  and floor.  This sytem should have a subsurface drainage network going to a sump pit or daylight.  This system should include gravel embedment of the drain pipe and at least 6" of gravel under the floor to act as a capillary break covered with a heavy mill membrane that will not puncture with reinforcement or finishers walking on it.  Here are some drainage details from W.R.Grace:


The exterior of the footing should have a drainage sytem well below the level of the finish floor.  The wall should have a waterstop cast into the footing.  The exterior juncture of the wall with the footing should have a concrete or mortar cove to send any water to the drain pipes.  After the wall is damp/water proofed this pipe requires a gravel pack with a geotextile cover to keep the system from silting.  The drainage system must go to daylight (preferred) or to a pump.

Damp Proof.  Usually emulsified tar, hot tar, or  rubber based paint.  These can be troweled on, smeared on, or sprayed on.

Waterproof.  Usually requires a membrane of some type.  Bitumen/rubber/ here are some offered by Grace:
<http://www.na.graceconstruction.com/product.cfm?mode=c&id=137&did=11>

The damp/water proofing must be protected from backfill damage with some type of protector board.

The effectiveness of the waterproofing can be enhanced with the use of a drainage sheet that directs any subsurface water to the drainage system.  Grace makes several as well as Enkadrain.  Most of these can function as the protection board and the geotextile.

There is some good reading available at the concrete network:
<http://www.concretenetwork.com/concrete/waterproofing_concrete_foundations/>