Using Foam board to insulate conrete block walls???

Question

Ok I plan on using 3/4" foamboard to insulate two block walls in a bedroom.
1) How do i attach the foamboard to the walls?
2) I plan on using 3/8" drywall to finish the rooms is this a
good idea?
3) Should there be an air gap between the block-foamboard-
drywall?
4) Should I put a plastic barrier between the foamboard and
drywall?
5) Should i do anything to the block wall before adding the foamboard?? like paint?
Thank you all in advance for your responses.

Answer 1

I have the same problem with my concrete party walls that i want to insulate. Looks like you have to attach furring strips to the wall with a nail gun (think of laying boards flat on the wall like a frame) Just have the boards be as thick as the foamboard and then you can set them right in there. then you would have to attach the drywall to the furring strips with more nails. an air gap between the foamboard and drywall would be good so maybe if you are using 3/4 in foamboard, your boards could be 1 inch thick and then you have alittle airspace. Unfortunately, my door is butted right up to my wall, so my only option is maybe glueing drywall with construction glue, or mass loaded vinyl barrier.

Answer 2

The area where i am (Edmonton Canada) this is actually a common building practice. But instead of concrete structure we use wood, but the basic building science is identical. Things you can look up website wise are (these are Canadian sites) are the National Research Council Of Canada, R2000, and Built Green. What you need is extruded polystyrene (rigid insulation). It comes in various thicknesses 1", 1 1/2" and 2". The R value (a thermal resistance rating) of R5 per inch. Typical wall construction should be a R value of 20. The rigid insulation is easiest to install by Hilti nailing it to the concrete wall. The nails need to have a washer (plastic) on the end to hold it in place. You can you adhesives, but be careful PL premium will eat the insulation but i believe PL400 works. You'll have to find your equivalent where you live. I would recommend a 2" minimum rigid insulation installation. The exterior finish can then be applied over it in the same manner as the insulation was installed. Hilti nailer's can be purchased at most home reno stores. All they are, a nail (strong enough to not bend when hitting the conc.) and a charge (similar to a 22 shell, just without the bullet). The rigid insulation is available from company's like Dow Corning. Rigid insulation is termite resistant and mold resistant as well. Good luck

Answer 3

Sounds like we're not alone.
Had some very cold outside block walls & used the same basic approach.
I did not take down the existing drywall & was able to screw & glue the furring strips to the existing drywall & whatever existing furring I could locate .
Used some adhesive on the foam but for the most part it was just press fit between the strips.
Thickness depends on how much space you are willing to give up,
I went w/ 3/4' furring & foam w/ a vapor barrier between it & the new drywall.
1/2" drywall is commonly use on walls , it made it a little easier to trim around windows, but 3/4' is ok.
Found extension collars for the wall outlets which made life easier.
Also used expanding foam around electrical boxes & windows where I could.
From the block, ended up with an uninsulated1-1/2" gap + 1/2" original drywall + 3/4" insulated furred out space + new 1/2" drywall.
If you have'nt already taken the existing drywall down ,this is an easy way to go & you get a little extra from what's already there.
It worked out well.
Best regards

Answer 4

You need to be very careful if this is a basement. You don't want to end up with a moldy mess. If your basement has any moisture problems you must correct them first otherwise you are tossing money into the garbage.

First don't use any adhesives that contain strong solvents like liquid nails, it will melt polystyrene. I would use expanding polyurethane foam to secure the foam panels to the walls. You can also use a polyurethane adhesive like gorilla glue.

You should also use expanding polyurethane foam to seal the joints between the foam panels. This will prevent air/moisture migration.

You should then build a min 2x3 wall 1" back from the foam and then attach your drywall to the wall.

The bottom plate of your wall needs to either be treated lumber or you need to place sill gasket under it to prevent any moisture form the floor rotting the wood.

When you hang your sheetrock leave a 1/2" gap between the floor and the sheetrock so any moisture in the slab will not get absorbed.

Answer 5

Liquid Nails For Foam

Answer 6

Attach the foamboard with liquid nails.
3/8 is fine.
You don't need an air gap.
Put plastic over the foamboard
Good luck

Answer 7

1) Use liquid nails which is a glue
2) You're gonna need a space in between and you'd need to do alot of work. Not a good idea. Takes ALOT OF TIME
3) YESSSS The air is provided by the 2 by fours being framed out
4)Not sure. You only need it where there's constant water falling on it.
5) Make sure you remove the grease on the wall.

One thing. WHY WOULD YOU USE FOAMBOARD!!!!!!!!????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????
These answers were provided by a 21 year old who has worked in construction. We are not responsible is anything goes wrong.

Answer 8

Jazz is correct, completely. Don't know who the 21 year old construction worker is employed by, but I hope he doesn't work in my area.