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Community and Q&A

Cuts in Foundation Drainage Board

qofmiwok | Posted in Green Building Techniques on

My contractors installed drain board over the foundation membrane before doing the below grade penetrations.  So now they are cutting flaps in the drain board to seal the penetrations before backfilling.  Drain board has no instructions to “seal” the connections, so as long as the flaps stay closed while being backfilled, will that be okay?

I think some tape would at least be helpful to hold the flaps in place while the backfill happens.  It has a filter fabric over it though so I’m not really sure what would stick.

Products are Henry WP200 and DB200.

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  1. user-2310254 | | #1

    Not an expert, but the Henry data sheet has instructions for overlapping the drainboard. It states the overlaps should be taped on the backside with Blueskin PreSeal Tape 50S. Seems like a good idea to me.

    1. qofmiwok | | #2

      Did you happen to save a link to that? It absolutely doesn't say that on the installation instructions I found online, but they have a frustrating variety of different info and it's difficult to get to it. (It might be different instruction sheet in that that ours has filter fabric attached to the drainboard.)

  2. user-2310254 | | #3

    I gave it a closer read and realized I was looking at the Preseal and not the DB. If you have the Preseal attached to the foundation, that is the primary waterproofing layer. (My interpretation.) And the DB is there to address hydrostatic pressure, which is why the instructions tell you to simply to overlap layers. That said, I think the situation is different if the installer has cut the DB and there is no overlap layer. I'd ask to have those cuts taped just to be on the safe side. Water always looks for the path of least resistance.

    1. qofmiwok | | #5

      Ah, thanks. Yeah, I agree. They also cut flaps in the DB to get access to do penetrations. I'm just not sure what kind of tape would stick to either bumpy plasticky drainboard or the filter fabric on the other side.

      1. user-2310254 | | #6

        The PreSeal seems a good bet, but I would call Henry's technical support line for advice.

  3. GBA Editor
    Kiley Jacques | | #4

    I am also no expert but I agree with Steve. They screwed up their construction sequencing and are cutting into a product you paid good money for. They have you worried and spending time researching possible outcomes (arguably their job). In your shoes, knowing enough, I'd ask them to tape the cuts. You didn't buy a cut-up drainage board.

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