Sealing Basement Sill Plate to Block Wall

Old 11-04-14, 10:59 AM
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Sealing Basement Sill Plate to Block Wall

Last winter I started insulating my Rim Joist bays in the basement with 2" XPS board and caulking with GE White 3-Hour Ready Silicone. I then moved on to sealed the entire foundation sill plate to the top of the cinderblock walls. I also caulked every single gap and seam I could find in the rim. I just checked last night, almost 1 year later, and noticed the entire bead of silicone separated from the cinderblock only but not the wood sill plate.

Recently I bought 6" 3M 8067 Flashing Tape to experiment with. That flashing tape is awesome. It sticks to anything, stretches, seals things air tight. The only issue is that it smells extremely bad and I mean BAD!!! So I ripped down the 10ft of tape that I experimented with. I couldn't bare the smell.
  1. Should I strip the silicone and reapply new silicone to the sill and block?
  2. Should I use something like Liquid Nails instead of silicone?
  3. Should I use a different adhesive tape?
  4. If I use an adhesive tape is there anything that sticks as good as flashing tape without the crazy smell?
Old 11-05-14, 03:13 AM
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how long did it take for the odor to dissipate ? odd the silicone didn't adhere - that suggests either dirty surface OR wetness
Old 11-05-14, 06:48 AM
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The odor from the Tape? After a week it never went away and probably would never go away. Whatever makes the flashing tape so stretchy and sticky is making the odor.

I vacuumed and scrapped the top of the block wall as best I could. I may just strip and silicone again.

Unless someone has a brand tape recommendation. Possibly the red tape made for XPS is sticky enough to stick to wood and concrete walls?
Old 11-05-14, 06:59 AM
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You might try a polyurethane or butyl rubber caulk. They will pretty much stick to anything...and I mean anything! Fingers, walls, clothes, tools, etc.
Old 11-05-14, 07:03 AM
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With silicone, polyurethane and butyl caulk if you keep a rag wet with paint thinner handy - you can keep your fingers clean along with wiping up any errant caulk.

What is the humidity level in the basement? wood will expand/contract with humidity changes and might explain the caulking failure.

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