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Community and Q&A

Rain Water Coming Through Expansion Gap in OSB

Trying2save | Posted in General Questions on

Ok pro’s
Unit : Detached garage
Location of problem : exterior wall
Current project : insulating garage

Scenario: ok so hopefully you have an idea of the setting I want to use a combo of fiberglass wall batts and for smaller areas in the framing use canned spray foam. So for starters there is some type of lining between the framing and the sheathing similar to the thickness and  flexibility of sand paper that was not affixed to the osb overlapping in the cavities in some areas allowing wind to come through so I Applied dynafles 230 sealing/caulk and applied flashing tape  to try and make it a continuous barrier. I did this while I was inside the garage and not knowing any better I also filled the expansion gap between the osb which now I know is not a good idea but thats where all the outside wind was coming through. I let that sit and cure over night the next day I put up about (9) wall fiberglass batts and filled in 2 other narrower cavities with some expanding foam and again let that cure over night. And that brings us to today. It rained for the majority of the day and after work I came back to the garage to finish the insulation and found that the majority of the wall batts I installed were wet at the bottom and notice water around the footboard. Now, luckily the batts are not completely ruined but it just sucks knowing that all that progress was for nothing.
So I begin drying the wet area and will have a fan run over night to hopefully take care of the rest of the water.
Where I think I went wrong was filling the expansion gap of the osb
with the spray foam and the tape. I did notice water dripping from the tape in some areas.. what do i do? Should I undo everything ? Won’t water rot out the osb and footboard if more water continues to seep through? Do I have to take off siding and replace weather barrier? Can I just apply caulking to cracks on the outside siding to stop the rain from getting in. This darn garage getting pretty drafty. I probably have enough material to do this project 4 times but I’d rather not do that and at this point I rather just finish and hire outside help. thanks again for taking on this question and I hope to get this project done soon. Probaky bes t to maybe do. Video call so I can show you. Let me knownand happy new year!

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  1. Expert Member
    Peter Engle | | #1

    Did you ever notice water getting through the wall before you started insulating? If so, the siding, flashing and weather barrier are installed wrong and the only real fix for that is to take it off and start again. It is still common in some parts of the country to install vinyl siding without a weather barrier underneath, even though that practice has been prohibited for quite some time.

    If the water problem only started when you insulated, it might be condensation from interior moisture. Because insulation reduces heat flow through the wall, adding insulation makes the interior side of the sheathing colder. If you have warm and damp air in the garage, it can move through the fiberglass batts and condense when it contacts the colder sheathing. This is one reason why it is never recommended to leave fiberglass batts exposed. One of the "smart" membranes installed on the interior would limit this behavior. If you go that route, you will probably also want to add drywall or another wall covering to protect the membrane from damage.

    1. Trying2save | | #2

      It is definitely from the rain coming from the outside. It a pretty old unit and I did notice hair line cracks in the siding in some parts. The weather board are pretty beat up and spongy. I live in Central Texas so insulation is going to help keep it cool over the summer. Currently I can feel slight drafts coming through those expansion gaps. We just looking at the footers of the frame and the OSB I dont see and mold or discoloration. What would you do if it was your garage? Do you suggest removing a small panel of the siding and see what I dealing with? Maybe add new weather barrier flashing paper behind the siding and seal the cracks on the siding with some dynaflex ultra? Or maybe just trusting in the dynaflex ultra to do the job and look for some weather tuff paint?

  2. Trying2save | | #3

    This is what it looks like on the inside. You can even see water marker on the lining

  3. andy_ | | #4

    Definitely need to find the source of the water. ...and no, not the clouds, but where the water is making its way inside. Could be the roof, gutter, siding, or even ground level pouring through the sill plate. Find and remedy the leak before even thinking about insulation.

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