ᐅ Bituminous Coating / Perimeter Insulation for Waterproof Concrete Basement

Hello everyone,

I have a question regarding the bitumen coating for a waterproof (WU) basement.

Currently, our basement is being cast on site with waterproof concrete (WU concrete). When I asked the structural contractor on site, it seems that only perimeter insulation is being installed WITHOUT a bitumen coating (even though this is specified in the scope of work). He said that this is not necessary for waterproof concrete or a waterproof basement.

Before I bother my general contractor about this, I would like to know if this can actually be the case (perhaps the scope of work is still quite general and a bitumen coating is truly not required for a waterproof basement?), or if this is simply a cost-saving measure.

For waterproof basements in general, is perimeter insulation alone sufficient? Is a bitumen coating advisable or necessary?

Where exactly do you want the bitumen layer? In our case, bitumen was used to glue the perimeter insulation to the waterproof concrete (WU concrete) and to seal the joints of all insulation boards with bitumen. However, there was no full-surface bitumen layer applied in front of the perimeter insulation. Perhaps the previously mentioned "glue layer" is what you refer to as the bitumen mastic? It is important (and only correct if properly executed) that the perimeter insulation is waterproof.

Alternatively, you can also install a dimpled membrane in front of the perimeter insulation. This also protects the insulation from water, and if necessary, you can even do this yourself.

Strahleman schrieb:

Where exactly do you want to have the bitumen layer? In our case, bitumen was used to bond the perimeter insulation to the waterproof concrete as well as to seal the joints of all insulation boards with bitumen. However, there was no continuous bitumen layer applied before the perimeter insulation. Maybe the first mentioned "adhesive layer" is the bitumen coating you are referring to? The important thing (and only correct when properly executed) is that the perimeter insulation is waterproof.

Alternatively, you can also install a dimpled membrane in front of the perimeter insulation. It also protects the insulation from moisture and can even be done as a DIY task in some cases.

Honestly, I have no idea... 😀

I thought that there would be a bitumen layer under the perimeter insulation?

Our building and service specification says the following:

So I assumed that this is an "additional" waterproofing layer.

How do you interpret this?

A dimpled membrane is still included in our construction and performance specifications, so it will also be installed: