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Insulating my basement, question...

egghead2004's Avatar
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02-09-06, 08:48 AM   #1  
Insulating my basement, question...

Finally to save on wood consumption, I am going to insulate my basement walls and floor. I've been researching for a few days now on trhe proper way, but there are so many varying opinions. I just want to run this by everyone to see if this might be the right way to go.

I read this article, http://www.buildingscience.com/resou...stems-2002.pdf
that is my basis for the following steps.

I have a 4 year old house, fully poured concrete basement. I have no cracks in the walls, just slight ones where the floor and walls join, no leaks though.
I have a perimeter drain so the water does not stand near the walls.

Step 1 - glue 3/4" extruded polystyrene to the walls and top of walls.
?What type of glue?
?Should I stop about 3-5 inches from the floor?

Step 2 - Frame 2*4 walls up using PT againts the floor.
?How close to the rigid foam?

Step 3 - insulate with R13 fiberglass batts, non faced, no vapor barrier.
?How do I support the insulation in the cavity?
?can the fiberglass insulation touch the rigid foam insulation?
Step 4 - Hang 1/2 inch sheetrock, mud, and paint.

For the floor;

Step 1 - install PT 2*4 laying flat 24" on center.

Step 2 - install extruded poly rigid foam between the 2*4s

Step 3 - cover with 3/4 " T&G plywood.

Is that it?


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leventmine's Avatar

Join Date: Jan 2006
Posts: 33

02-09-06, 11:14 AM   #2  
Like you said there are so many ways to do things but it sounds like you have a dry basement which in my opinion is the most important.

I did my floor first but instead of PT lumber I put down a 6 mil Poly barrier then nailed 2x4s flat with 1.5 inch rigid foam insulation between then the plywood. Stagger your edges with the Plywood.

Now I am framing my walls with 2x4s ( this way you are framing on your built up floor rather than concrete) And I will use R-13 faced insulation then drywaal.

It sounds like you are on the right track.

Good luck!

DIYER's Avatar

Join Date: Oct 2005
Posts: 36

02-09-06, 11:21 AM   #3  
IStep 1 - glue 3/4" extruded polystyrene to the walls and top of walls.
?What type of glue?
?Should I stop about 3-5 inches from the floor?

Step 2 - Frame 2*4 walls up using PT againts the floor.
?How close to the rigid foam?

Liquid Nails makes a glue for foamboard. Use only a glue for foamboard as i have read that other glues will break down the foam. I put my 2x4's directly against the foamboard. Owens Corning makes a product called INSULPINK especially for basements. It has sort of a tongue and groove so the edges fit perfectly. I also taped the joints with Tyvek tape.

doug thomas's Avatar

Join Date: Jan 2006
Posts: 104

02-09-06, 11:29 AM   #4  
I hope Leventmine's house isn't new, because his slab will continue to bleed moisture toward the living space for a few years. At least it would if the poly weren't there. So now it will just accumulate. And faced insulation in the walls isn't much better than batt+poly.

As long as your slab is below grade & you have some sort of perimeter insulation, sutffing rigid in between the floor rafters won't really help much, or make much of a difference. You're already pretty well covered.

As for the walls, the batt should definitely touch the rigid. I don't see why the lumber couldn't touch the rigid too. Batts would have to be friction fit.

Concretemasonry's Avatar

Join Date: Mar 2005
Posts: 6,125

02-09-06, 11:48 AM   #5  
Insulating my basement, question...

If you are building and insulating, there is only one good place to use foam board or bead board(EXPANDED polystyrene) - in the cheap throw away cooler for your lunch!!

Use rigid EXTRUDED polystyrene (blue, pink, etc.). It insulates betterand is easier to handle and work with.


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