Basement finishing

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  #1  
Old 11-14-16, 05:30 AM
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Basement finishing

Hey guys think I'm putting this in the right place I am getting ready to stud my basement.all the exterior walls down there have been covered in 1/2 in styrofoam..my question is should I remove all the foam first or just leave it up also should I us 2x3 or 2 x4 thanks for the help
 
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  #2  
Old 11-14-16, 07:21 AM
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Basements are one area where moisture problems can ruin the results. Unfortunately, almost all basements have moisture problems, even when they look dry. Moisture vapor will pass right through concrete and even that 1/2" of styrofoam, assuming it doesn't have a foil facing.

Your location will tell us if the 1/2" is sufficient and how much total insulation is needed on those walls. Too little rigid and lots of air permeable batt insulation and you end up with a condensation potential.

Tell us what climate you are in and about any known moisture issues.

Bud
 
  #3  
Old 11-14-16, 09:40 AM
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I'm in ontario canada and no there is no foil on the stuff also the roof off the basement is in the same thing also we are all sand with no drainage around base of foundation or a sub pump
 
  #4  
Old 11-14-16, 10:31 AM
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I can't quote Canadian codes and requirements, but the southern area of Ontario should be similar to the US side and there they are specifying R-19 for cavity plus rigid. You will need to check the codes governing your location.

As for the thickness of rigid when used in combination with batt insulation a rough guide would be at least 1/3 of the total r-value should be from the rigid. The rest can be batts.

As for moisture, all basements have to deal with moisture vapor. If you have a green lawn your soil has moisture and that moisture level wants to equalize with the inside of your basement.

Here is a good reference. http://www.nrel.gov/docs/fy13osti/55802.pdf

Bud
 
  #5  
Old 11-14-16, 12:43 PM
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Thanks Bud the reasing material was more worried about leaving it up I couldn't tell u how long it has been there or how is even fastened will that cause a bigher moisture problem in the long run I know the basement is extremely dry to the point I run a humidifier down there I guess I will have to do some more poking around here
 
  #6  
Old 11-14-16, 01:37 PM
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Needing to run a humidifier is good, strong indication of very little moisture. Along those lines, they recommend avoiding a plastic vapor barrier on basement walls to prevent small amounts of moisture from accumulation. Check local codes as some will require a vapor barrier, even though I disagree.

If the foam on the wall is pink, blue, or white, it should do no harm and if it is still up there after a few years doubtful it is coming down.

I would add another 1" layer of rigid over what is there. Then stud wall directly against the foam, no gap needed. Then, I like 2x4 wall with 3.5" of Roxul.

Be sure to air seal where the house rests on the foundation, notorious for hidden cold air leaks. And the detail some rigid insulation into the rim joist cavities.

You are the boss, I can only suggest.

Best,
Bud
 
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