Basements:waterproofing against damp proofing

Note: This is an article pertaining only to asphalt-based waterproofing products.

 The terms ‘damp proofing’ and ‘waterproofing’ are still used interchangeably even by people of the construction industry.

Though, these terms are not equivalent.

Actually they are very distinct.

Damp proofing refers to traditional products usually based on unmodified bitumen.

These bituminous products which are used for many decades to waterproof basement/foundation walls were originally conceived as an auxiliary product for the road construction industry. Their use for basements waterproofing (better damp proofing) was somehow accidental.

 Damp proofing materials:

 - achieve a thickness of about 0,3-0,5mm

- cannot intercept water which is even under minimal hydrostatic pressure

- can control the soil moisture and can be regarded as a vapor barrier

- cannot span even the narrowest discontinuities both in present and future time. If the substrate cracks, the damp proofing layer will crack also. These products become brittle with passing of time and also in colder temperatures. This means that a possible increase in their consumption rates will not automatically convert them into waterproofing products.

They will still remain pseudo-waterproofing products.

On the other side bituminous waterproofing materials:

- are also based on bitumen but their properties are enhanced with the addition of polymers. Thus they become elastomeric.

- They can function as waterproofing products as well as vapor barriers.

- These products are elastic, can retain their elasticity even at very low temperatures and can easily bridge cracks and any kind of discontinuities of the substrate.

- Their average thickness is 1-1,5mm and with this thickness and their elastic structure they can withstand hydrostatic pressures.

- Good waterproofing products have an average, expected, functional life of 15-20 years. Conversely damp proofing products will last no more than 5 years.

All products need a smooth, dry and clean substrate without protrusions, honeycombs, wall ties and cracks.

Application can be effected by brush, roller or spray.

It’s absolutely vital that all the necessary surface and subsurface water management measures should be taken.

The work will not be complete if a suitable protection layer won’t be placed over the waterproofing/damp proofing layer.

Among the options, we can consider simple dimpled membranes, dimpled membranes with geotextiles or other equivalent geosynthetic composites, special foundation boards etc.

 Chris Strogilis

Civ. Eng. – MBA – DipM

http://maconwaterproofing.blogspot.com/