Fastening Foam Board to Concrete Foundation Walls
Pott0120
| Posted in General Questions on
My builder is concerned about how he would glue the 2” foam to my basement walls before installing the framing. He said the metal tabs from the concrete would all need to be cut off. He believes 1.5 inches of spray foam would be more cost effective. What are we missing? Is there an easy way to install eps board insulation against a concrete wall or should we use spray foam?
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Replies
Hi Matt,
For the building it may be cheaper to use spray foam once they factor the labour of cutting metal tabs and gluing the foam to the wall. The benefit of spray foam is you'll get a good seal which will act as your vapour barrier (closed cell) which is a big plus for a basement.
I just installed myself some EPS panel on my foundation stem wall and I use Lepage PL300 adhesive which is rated for foam. It held it place without any issues until the gravel was backfill and packed.
Arnold
Matt,
Depending on what type of concrete ties were used there are two solutions. One is to push a piece of EPS onto a tab and see if it will penetrate and temporarily support the foam while the glue dries. The second is to remove them with a 4" angle grinder. For an average basement that should take maybe an hour.
> My builder is concerned about how he would glue the 2” foam to my basement walls before installing the framing.
With glue. :-) Joking aside, canned foam construction adhesive works very well for this.
> He said the metal tabs from the concrete would all need to be cut off.
As someone else mentioned, depending on what these look like, they might be able to be shoved right into the foam.
> He believes 1.5 inches of spray foam would be more cost effective.
Good luck getting a contractor to effectively spray 1.5" of closed cell. You'll end up with some spots under 1" and some over 2".
> What are we missing?
Your contractor doesn't want to do something they haven't done before and would rather sub the job out.
> Is there an easy way to install eps board insulation against a concrete wall or should we use spray foam?
Foam adhesive and kickers to brace against, maybe a fastener here or there to tack things to the wall.
If you use spray foam, I would frame first, leaving a 2" gap between framing and the wall, and then have them spray up to the back of the studs. 2" is about the minimum thickness they can spray, and you'll end up with 1.5"-2.5", overall. Because the framing is in place first, you don't need to worry about the high spots. If you spray first, the high spots would need to be shaved down which is a royal pain with closed cell.
Read this thread on the topic. Martin Holladay, Mike Maines, and others share their ideas on best practices: Fastening Rigid Foam: Glue vs. Fasteners.
I used this tool at my house it is very fast and affective. Ramset let me use the tool for no charge I just had to buy the fasteners.
https://www.youtube.com/watch?v=ZNnfn3PeX-M&ab_channel=IDIDistributors
There is no skill required to remove the form tabs bend them back and forth with a hammer and they fall off on the third bend. That’s 90 minutes of no skill labor tops. The last thing you want is steel coming into your insulation.
Walta