Insulating Basement

[RedNeck Wrangler]

I'm going to insulate my basement with 4x8 foam sheets. What is the best way to attach them to the cement walls? I was thinking screws with large washers or do they make something specifically for this? Is 1.5" insulation thick enough? Do I need to tape the seams? Thanks for any advice.

 

[Couderay80]

Have you seen the insulated concrete forms. ICF's are a good way if not the best way to insulate your foundation and walls. With a couple of friends you can form your basement walls in a long day. The best part is no heavy concrete forms to place and take out,as the lego style foam blocks stay in place. Many different manufactors out there to choose from. The one thing I didn't take into consideration when my walls were up is I had to go back and drywall the inside of the basement walls, do to fire code, before we could occupy. I recommend the steel backing plates as to the plastic when screwing in the drywall,as they vary between manufactor's. The ICF's have different styles of interior options, steel banding as opposed to plastic,re-bar supports and a few others. Google ICF's and let the adventure begin.

 

[elmoleaf]

Is your basment going to be finished or not? Existing poured concrete foundation walls? Any existing dampness or water issues?

These all make a difference on how you proceed. If it's going to be finished space, then consider a wood stud system tight to the concrete, with foam infill between studs. The studs will allow attachment of gypsum board or paneling, routing of electrical wires etc.
If you have solid concrete walls, construction adhesive alone may be sufficient to secure foam. However, there may be a code issue with leaving exposed foam because of the fire hazard. Investigate if it needs to be covered with gypsum board...if so, you'll need some way to secure the board.

If you have dampness issues, correct those problems first. Look into DryLoc or similar dampproofing paints that have sand in them.

Taping seams will help keep a continuous vapor barrier and eliminate possible condensation behind the foam.

 

[RedNeck Wrangler]

Existing walls with no moisture problems and it won't be a finished basement. I'm installing a wood stove in basement and trying to reduce heat loss.

 

[InTheRockies]

I had to replace the insulation in the unfinished utility room in the basement of the house I owned back east. I used the foam sheets and attached them with a construction adhesive rated for the material. It worked well. The foam also seemed to be more efficient for the application than the fiberglass blanket that the builder had used.

 

[begreen]

If the panels tightly abut each other, there shouldn't be a need to tape the seams. In our crawl space I used the heavy duty Liquid Nails, rated for foam use. Each panel was given a very healthy application of the stuff, then propped in place until the glue fired off. It's still holding very well after a couple years. We also caulked the sill carefully and then put fiberglass batting in the rim joist area.

 

[bruce]

icf in one long day?
i dont think so
i do it and dont assemble them in one day, not a do it your selfer idea

 

[woodburn]

Great point about caulking the sill and batting the rim joist area. I would do just that and glue the boards right on. If you're throwing a stove in, you might end up spending more time down there. I would consider 2 x 3 wood or metal framing in case you decide to finish is off. I personally would tape the seams. Good luck.

 

[velvetfoot]

I am doing this now slowly.
A couple of things I didn't think of was the added thickness for the door and little window.
I tacked 2" tongue and groove sheets onto the wall with foam compatible glue.
I didn't think of a way to keep pressure on the sheets. They stuck but the hardened dots of glue might have acted as spacers.
I didn't think it was important because they probably did get flattened and I am now installing 1 x 3 furring strips to strap the sheets to the wall.
I am using 5 each 4" long 1/4" diameter tapcons per strap.
I am drilling the 3/8" holes 1 1/4" or so into the concrete with a rotary hammer drill I bought at Harbor Freight for about 80 bucks-it uses a drill format called SDS, which I knew nothing of before-a Bosch bit at the hardware store was 10 bucks.
I taped the joints with Tyvek tape before installing the furring strips over it.
I am not sure what I will do in the rim joist area. It currently has fiberglass. I hate handling that stuff.
My plan is, after I figure our what to do with the window and door sills and maybe enclose the stairs so I can hang some suspended ceiling, is to install sheet rock on the furring strips.
My plan is to use a router to make grooves in the foam to put in the existing power wires, and fasten them with staples, and then cover it with the sheetrock and use old work boxes.
You have to cover the foam with 1/2" sheetrock for fire reasons, in most cases. Not sure about a crawl space.

That 1.5 wallmate stuff seems to get beat up pretty good at the store, plus the furring strips give you some more space.

I'm thinking now I should've washed the walls down to kill potential smelly organisms; oh well.

I don't know if this will work, but I'm giving it a whirl.

What kind of lighting, ceiling and floor and those sills are what consume my thoughts now.

 

[bostonbaked]

Just so you'll know they now make a wallboard/sheetrock that uses no paper in the process. The paper on the old time stuff is what mold feeds on. In damp places it ruins the job over time. If you look around I believe the box stores now sell it. I also agree that the code. in Ma. at least doesn't allow the foam to be left exposed. At least that's what they told me and I was using it in a garage.

 

[velvetfoot]

My HD doesn't have it. The covering is fiberglass-cutting they say is itchy and it's hard to get a smooth finish.

 

[bostonbaked]

I have not used it . Just heard about it a while ago. May be they use for skim-coat plaster jobs. That could be why it's not smooth. Just a guess.

 

[woodburn]

I think you're talking about something like densarmor plus- they carry it at LOWES.

 

[richg]

My HD doesn't have it. The covering is fiberglass-cutting they say is itchy and it's hard to get a smooth finish.

I have used the stuff on a number of jobs, and yes, "itchy" would be a good way to describe it. It cuts better than sheetrock, holds screws better, and paint sticks to it like glue. One coat of primer and finish coat and the surface is just as smooth as regular sheetrock. I prefer densarmor over greenboard.

 

[velvetfoot]

Rich, how do you cut it? Not scoring it like regular sheetrock?

 

[richg]

It cuts the same as sheetrock.

 

[velvetfoot]

Cool.
I guess the fiber issue would be more in play when cutting openings?
Still I bet less than working with batts of the stuff.
I happened to be at a Lowes yesterday and looked at it.
The surface does appear a tad rough, but amazing that it contains no paper.
It was ~$13 (US) per 8' sheet and they had only 4x8's.
Sounds ideal for the basement.

 

[velvetfoot]

I bought some ~ 18sheets of the DensArmor Plus, what I could fit on the weak utility trailer I have, but have to do some more sheet foam work.

I've decided to put another layer of 2" foam over the first layer of strapped on foam.
I've used the router to make a ~2.75" x ~.75" groove down the middle of each piece to go over the furring strips.
It seems to work. I'll tape the and/or glue the foam joints and the sheet rock will hold down the second layer of foam. That's the plan anyway.

I've cut some pieces of foam for a rim joist bay and that seems to work too.
I have some questions there too, but maybe I'll do a little more searching and start a new thread just on rim joist sealing.

 

[d.n.f.]

Have seen a few basement rim joist jobs (ooh that sounds dirty) and most use spray foam (the can stuff) to seal the rim joints that were done in rigid.
Works way better than caulking.
Plus one can can seal a lot of cracks.

 

[semipro]

RW,
See https://www.hearth.com/talk/threads/32045/

I referenced 2 great sources of info on this subject.

Semipro