construction/insulation question (LONG)

[dwcopple]

I have a ranch style home built in 1960 and it has a block walled basement that I have finished half of for a rec room/office. When sitting at the chair at my desk down there I felt a gust of cool air. I tracked it down to the top of the block wall near the sill plate. I got on a step stool and shined a light up there and noticed a gap 32" long in the expansion joint material used between the block and the wood sill plate. I could see daylight in this gap and the backside of the old wood siding that is now covered with vinyl siding.

This is on my west wall (end of the house) below the master bedroom and also there is another 32" gap below my daughter's bedroom on the same west wall. These two rooms are always kinda drafty and cool feeling compared to the others. Why were these gaps there? I asked the building help at Menards and asked a friend of mine that does waterproofing of commercial buildings and both said it shouldn't be like that. So I bought a slab of expansion joint material today and mallet tapped it into place at both spots and sealed around the area with expanding foam. I did the right thing right?

 

[LS2JSTS]

I would seal it on the outside as well to prevent cold air from infiltrating the block wall and forming condensation.

Are there lag bolts through the sill plate along the walls in question? I assume this is the older black thick tar paperish material and not the newer blue foam stuff?

 

[BobsArmory]

You did good

 

[dwcopple]

Just went down and checked it. Sealing good with no air leaks felt. The material in question is a 1/2" thick carboard type substance with a dark black/brown coating. Typical expansion joint stuff seen between sidewalk or driveway cuts.

 

[dwcopple]

Originally Posted By: LS2JSTS
I would seal it on the outside as well to prevent cold air from infiltrating the block wall and forming condensation.

Are there lag bolts through the sill plate along the walls in question? I assume this is the older black thick tar paperish material and not the newer blue foam stuff?

No bolts that I can see anywhere. Not sure how I would even access the outside to seal it. How would I get under the vinyl siding?

 

[LS2JSTS]

You can pull the siding off the bottom starter strip, if it's not too cold. I wouldn't mess with it, at the temps we have right now. Maybe in the spring, pull the gasket material back out and latex/silicon caulk on the outside where you saw/see light coming in.

As long as you got the new black gasket material all the way under to cover the web, you should be fine.

 

[Pop_Rivit]

Originally Posted By: dwcopple
Why were these gaps there?


Do they look like they were constructed in that manner, or is it the result of 50+ years of settling? Or simply poorly constructed?

Houses settle over the years and it can cause issues-some minor and some major.

If it looks like it was constructed with those gaps it may have been a misguided attempt at some sort of ventilation. During the housing bubble I helped supply the investment capital for a house flipping company, and the "ideas" that we found that some people come up with are truly astounding.


Originally Posted By: dwcopple
So I bought a slab of expansion joint material today and mallet tapped it into place at both spots and sealed around the area with expanding foam. I did the right thing right?


As long as it's a material that won't retain moisture you should be fine. If it can retain moisture and it does get wet (leaks, wind driven rain, etc) then I'd suggest replacing it with something better suited.

While you're there you might also consider insulating the sills all the way around the basement (if they aren't already insulated).

 

[dwcopple]

Originally Posted By: Pop_Rivit


If it looks like it was constructed with those gaps it may have been a misguided attempt at some sort of ventilation. During the housing bubble I helped supply the investment capital for a house flipping company, and the "ideas" that we found that some people come up with are truly astounding.


While you're there you might also consider insulating the sills all the way around the basement (if they aren't already insulated).
Went down to do laundry today and checked both spots out. No air movement whatsoever. Very nice! (Borat voice) I'm not sure I want to take time to insulate all the sill and rim joist areas right now. Would I really gain anything if they aren't letting any air in anyways? I plan on installing a ceiling into the furnished side of the basement in the near future too. Should I insulate the floor joists or is that pointless?