Dampproof vs waterproof – basement wall
user-7600779
| Posted in General Questions on
Hello everyone;
Quick Question: If a dimple mat is applied on the exterior side of basement walls as a water proof strategy is there any need to apply a damp proof bitumen paint between the walls and the dimple mat?
Or the dimple mat acts as water and damp proof layer?
Thank you in advance
ER
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Replies
Hi ER.
I believe that many code officials accept a dimple mat as the code-required dampproofing/waterproofing for a basement wall. However, the builders that I trust and spoke with while researching "Best Practices for Dry, Healthy Basements" prefer a belt-and-suspenders approach on basement walls and apply dampproofing/waterproofing to the basement wall before installing the dimple mat. The dimple mat creates an air space to relieve hydrostatic pressure and drainage plane for any water that gets behind it to run down to the footing drain.
+1 to Brian's comments above. However, dimple mat manufacturers do often provide techniques to use the dimple mat as the only water/damp proofing layer. Dimple mats with a scrim surface facing the soil provide drainage on the front side. You can also use dimple mat behind rockwool or foam insulation and in either case, the insulation bridges the dimples enough to create a drainage space. If you are using a dimple mat this way, you need to seal seams in the mat and terminate the top with a manufacturer-approved termination bar because you can't tolerate water getting behind the mat.
In my experience if you want a dry basement you must have a good drain too day light.
If you do not have a good drain the dimple matt is useless.
If where your house will be the only hill is the one that goes over the highway. I say skip the basement and pour a slab.
What it takes to build a dry basement is a very local question what works here may not work with your soil and drainage. If you trust your builder and he has a good track record you need to trust him. If you can’t trust him fire him now and find someone you trust.
Walta
The dimple mat alone will eliminate pressure that would push water into the wall. I expect that it will still allow some wicking of water through the wall.