Newbie Insulation/framing Basement Help - Building & Construction - DIY Chatroom Home Improvement Forum

Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Building & Construction


Thread Tools Display Modes
Old 11-10-2011, 11:14 PM   #1
Join Date: Nov 2011
Posts: 48
Rewards Points: 49

newbie insulation/framing basement help

I have been reading many posts on here with links to the building sciences sites that discusses insulation. I am in Chicago, so it can get a bit chilly.
I have a 5 year old home with typical poured walls and what I guess is called a "diaper." I have normal basement, not a walk-out, i.e. surrounded by soil on all sides. The home was built by a cookie-cutter builder where speed was way more important than quality.

1) If I understand correctly, the diaper is probably the cheapest way for a builder to adhere to the Code and also one of the worst ways to insulate the basement.?

I saw on another site where there was a "study" of this diaper and leaving 6" at the bottom open, allows for any moisture to dissapate. Mine has 6" open on the bottom, and in any event I will REMOVE the diaper to inspect the walls.

My last home had a wall tie rod and a separate crack that leaked in the unfinished basement, keep this in mind as I discuss below! :-).

2) My question with the XPS foam is what happens IF a leak develops down the will you notice it if ALL the joints are taped and the bottom sealed with expanding foam?? Won't the water simply build behind the foam wall?
Instead of a trickle, won't it eventually bust out in a torrent of gooey-moldy water?

3) Also, won't typical expanding foam absorb water and breakdown or do I use the fountain/pond new expanding foam that is impervious to water to seal the bottom of the XPS to the floor?

4) DO I use the adhesive for the XPS in vertical lines, so IF there is a leak, I know about where I have to open the wall, versus if I do a "Z" or criss-cross pattern it may channel the water and leak out 3-4 feet from the leak location? Does it matter, or is there a "best" way?

5) How can I frame against the XPS foam and leave NO airspace if my poured walls are wavey?

6) Is the current thinking that there is to be NO vapor barrier under the drywall, like the basement I had growing up as a kid? Correct?

7) Also, I got some advice to drylock the walls as a secondary protective measure...but won't that stop the walls from breathing vapor thru the XPS, or is the area at the top of the wall and the rim joist enough area for water vapor to escape?
Do I drylock or not?

Thanks and I apologize if I missed these answers elsewhere!

I'm the unlucky guy that always sees "Murphys Law" it seems! :-) and trying to head off any future problems!

Attached Thumbnails
newbie insulation/framing basement help-challenges-basement-insulation.jpg  


kree is offline   Reply With Quote
Old 11-11-2011, 09:28 AM   #2
Join Date: Oct 2011
Location: Westfield, IN
Posts: 17
Rewards Points: 10

I wouldn't let the fear of future leaks behind walls stop you if you don't have leaks now and keep the grading around your house sloped away and keep those downspouts away as well.

Another great source for info on insulating with xps is He goes into a lot of detail on all the issues.

To answer some of your questions, as best as I understand...

With 2" xps you don't want another vapor barrier, it could trap moisture between it and the xps.

Even if a little moisture got between the wall and xps it wouldn't mold as their shouldn't be any food for it or much oxygen.

For glue, there are a lot of different opinions, but I don't think you need much. Maybe a couple dabs in the corners and middle to keep it up. Especially if you are framing over it and sealing the bottom. There is a concern about convective loops being formed by air moving behind the foam, but that only happens if you don't seal the bottom.

Don't forget to cover the top of the wall that is exposed inside the sill plate as well.

I cut my sheets 1/2 inch or so short to make room for the floor being a little uneven. Line up the factory cut edge with the top of the wall and fill the gap at the bottom with great stuff foam. Then use 1.5" foam cut to length to cover the top of the wall and extend over the foam on the wall. With a little glue on the sheets on the wall, the foam on the bottom and then taped to the foam on top, which is is glued on, they aren't going anywhere, even without the wall in front yet. The framing will really lock them in.


TimMauriello is offline   Reply With Quote
Old 11-12-2011, 01:02 AM   #3
Join Date: Nov 2011
Posts: 48
Rewards Points: 49

thanks, any thoughts on using drylock coating the walls?
kree is offline   Reply With Quote
Old 11-12-2011, 08:47 PM   #4
Registered User
Join Date: Mar 2009
Posts: 11,730
Rewards Points: 526

No Drylock on the walls, 2" foam if your location warrants it:

Airtight behind the foam board:

If any ads are present below my answer or words underlined/colored, I do not condone/support/use the product or services listed/linked to, they are there without my consent.
17,000 dryer fires a year, when did you last clean the inside of the dryer near motor or the exhaust ducting?
Gary in WA is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Newbie here finishing basement sanny651 Electrical 25 02-16-2010 11:23 AM
basement subpanel suggestions/advice desired ScottsName Electrical 4 02-26-2009 06:38 PM
A few Q's on Finishing My Basement - Is there a FAQ on this? ossrocks Remodeling 6 01-07-2009 12:21 PM
Basement Renovation Project Howdy Electrical 6 03-13-2008 11:07 AM
Basement - need to bust up about 1 ft deeper FallenAngel Building & Construction 7 08-15-2007 09:09 AM

Top of Page | View New Posts


Search Engine Friendly URLs by vBSEO 3.6.1