EPS rainscreen for walkout basement
Ithinkicanfixthat
| Posted in General Questions on
Green builders,
I am planning on waterproofing the below-grade portion of my walkout basement. I plan to use a water based adhesive to apply a HDPE based waterproofing against the masonry blocks. Next, I will add 2” of rigid EPS. Lastly, I’ll finish off the below grade portions with a dimple board. For the above grade portions, I will create a rainscreen using furring strips and finish with cedar siding.
Is it OK to drill through the waterproofing membrane in order to attach furring strips to masonry walls on top of the EPS ? Will this potentially ruin the life of the HDPE membrane?
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Replies
Yassir,
If you are only fastening the rain-screen battens above grade to support siding:
- Is there any advantage to extending the HDPE membrane high enough that the fasteners would penetrate it?
- Why does it matter if the membrane is penetrated by the fasteners above grade?
Do you not recommend only extending the HDPE membrane above grade?
I wanted to waterproof the masonry above grade to really remove moisture from the basement.
Yassir,
Above grade the foundation is protected from moisture by the rigid insulation, rain-screen gap and siding - just like framed walls above. None of them need a water-proof membrane on the outside.
If you’re really worried, squirt some silicone in the hole before inserting the fastener. The silicone will squish around as you tighten the fastener and help to seal the hole. I do this all the time on exterior masonry anchors to prevent water from getting in and freezing, then damaging, the masonry around the anchor.
HDPE itself is pretty impervious and won’t be damaged by a fastener hole or any resulting leaks. The only worry might be that if you stress the HDPE sheet around the fastener you could potentially tear it, but it’s a tough material and should be pretty resistant to damage in normal situations.
Bill