View Full Version : Insulating Basement Walls
I recently had a drainage system installed around the perimeter of my basement. The guy that did the work said I should attach furring strips to the foundation walls and attach a vapor barrier to that. He also said to run the bottom of the vapor barrier into the gap he left where the floor meets the foundation wall in case there is any seepage.
I have read some information on this blog that says I shouldn't do that. One says I should install foam insulation directly onto the foundation wall and put furring strips over that and then sheetrock.
My main question is... if I attach the foam directly to the foundation and happen to get water, is there enough room for the water to run down the wall and into the french drain??
Also, if this is possible, after I install the foam insulation can I build a 2x4 wall in front of that and if so do I need to install a vapor barrier at that point?
Thanks for any help and advice.
11-28-2008, 02:38 PM
Don't listen to that guy.
Frame with regular lumber or metal partition studs and leave an airgap for the wall to breath. You cannot afford to trap water between the foundation and your finished space. It will need to breath.
He is an idiot.
11-29-2008, 12:01 AM
Owens Corning have an excellent web site with good customer service!
Thanks for the advice but one more thing...
SO do you think I should frame the basement walls, attach a vapor barrier on the the back side of the wall but leave an inch or so between the wall and the foundation to help with air movement?
So you don't think the polystyrene foam should be installed directly against the foundation?
11-29-2008, 05:32 AM
i would use r 13 for insulation. leave gap for breathing. i have seen other people put poly down in a basement. but it always has high moisture so it basically just traps it and then condenses and runs down to the bottom plate. plus it is nice to have full wall for electrical and plumbing.
11-29-2008, 09:03 AM
Just use faced batt insulation between the studs. Get this plastic sheeting out of your head.
11-30-2008, 11:53 AM
Disagree with both.
- Do not, under any circumstances, use plastic anywhere. Basements should get vapor-retarders, not vapor barriers.
- Do not use batt insulation. Use closed-cell foam.
If you want all the ins & outs of why I'm saying this... download & read these:
Thanks Frenchie for those links... That seems to be the way I should go. Thank you everyone for all your help.
12-23-2008, 10:41 AM
No worries. In response to the PM you sent:
Hey Frenchie... I put a question out a few weeks back about insulating basement walls and I liked your idea best. I looked at the links you sent and they were great. Of all the professionals I spoke to, none of them suggested this. They all said to use batt insulation in a stud wall. I'm pretty torn on what to do so would you mind if I asked another question.
The thing that concerns me is if I attach the polystyrene to the foundation and I get a little water come through the wall, will it get caught behing the foam or will it find it's way down into the french drain. I plan on building a stub wall an inch off of the foundation so I'm not going to attach furring strips.
Does this make sense or do you have another suggestion.
I appreciate your help.
The first thing I want to say is that, if you have ANY water coming into the basement, you need to deal with that before even thinking about finishing the basement. There simply is no good way to finish a basement that leaks, you need to adress the water intrusion before doing anything else.
If you just want an extra measure of safety, by having a drainage plane behind the walls & under the finish floor... then... you could either use furring strips, or one of the drainage-plane sheet products, I suppose. I'm not sure what you mean about building a stub wall in this context, and why furring strips wouldn't work. Was that a typo for "stud wall", or...?
...I can't believe anyone's still using batt insulation in basements. That never ends well.
12-30-2008, 08:15 AM
very interesting links. I researched this heavily but somehow missed these. I had B-Dry do our basement couple years ago. Looks like they did everything correctly except nobody discussed with me jacking up the perimeter of the house to insert nonpermable membrane between top of foundation wall and house rim framing to prevent capillary action...... oh well I would have told them no way to that idea anyways.
Looks like I need to spray foam insullation down there next, cool!
12-30-2008, 09:18 PM
Keep mold food to a minimum! Mold loves wood 2x3s, especially if you have some nice batt insulation to keep it wet. Assume your basement will flood 1 inch or more and design accordingly. By flood detectors (they are cheap) and put them near trouble spots and of course the water heater, washer, etc. They won't prevent a disaster, but if you are home and hear one go off it could save you a major headache.
Ok, first, paint the walls with a waterproofing latex paint. (Ok, there is no such thing as waterproofing latex paint BUT it will hold out the dampness rather well. Plan on multiple coats. Next, as long as you do not have major water seepage glue the polystyrene to the wall, continuously. If there are a couple of spots where you think there might be minor leakage you can cut grooves into the back of the polystyrene in those locations to allow the water to drain to the floor. Anything more than minor leakage and you need to address your water issues before you can finish your basement. Tape all joints. Use the polystyrene without the foil vapor barrier. Finally frame with 2x3 metal studs and add blueboard sheetrock. Keep the blueboard an inch or more off the floor.
Thank you everybody for your responses...Yes Frenchie that was a typo on my email... Thanks for your response as well.
I plan on attaching the XPS to the foundation and using metal studs to frame out an inch or so away. One more thing if you guys don't mind...
I have a french drain around the perimeter of the basement with a 1 inch gap all around. Should I run the polystyrene all the way down the foundation wall flush with the gap at the floor or leave it raised a little. I'm not sure what to do because I don't plan on putting a sub floor down because I have minimal headroom and I want to make sure there is no way for the heat of the finished area to get out to the foundation wall.
I plan on carpeting because I have an uneven basement floor.
Any suggestions would be appreciated. Am I on the right track?
01-07-2009, 06:29 PM
If there is any chance of moisture in your basement I wouldn't put carpet down, I would install on a raised floor system
I have a stream on the property, our sump pump failed once & we had 6-8" of water in the basement. I'll never finish the basement, it will remain unfinished. We don't need the space with the addition I am building
Somewhere I saw solid foam board attached to sheathing attached directly to the concrete (foam 1st)
01-07-2009, 07:26 PM
Wedi is a tileable foam board that can be thinsetted directly to clean concrete then tile applied on top. It comes in various thicknesses. Panels up to 2" thick (and maybe more) are available.
01-13-2009, 10:25 AM
Interesting thread - We don't have a largish basement here in New England - there is more room there than we need, basically a big Ell 40' x 40' on the long sides with a 15' x 15' chunk missing. We used to get basement floods in the spring when the grounds was still frozen and the spring rains would force the water into the basement via hydrostatic pressure (you could watch the water seeping in between the basement slab and the walls (only one step better than watching paint dry). So we bit the bullet and had a perimeter drainage system installed - after spending a weekend putting all the current walls, lumber, sheetrock etc into a dumpster.
So now I am rebuilding, like I said, its more space than we need, so what I did in order to provide that ventilation that has been talked about, to provide access to my sills in case I need them, to be able to access my drainage system clean outs and to be able to access certain mechanicals etc is I stepped all my walls out from the foundation anything from 12" to 18", sure I lose some floor space but it seems to work for me. It's half done and so far I have had no issues whatsoever, nor do I expect any. My Hydro/Hygro (whatever) meter tells me moisture levels are very low still.
Construction is 2x4 KD Lumber with PT sills
01-13-2009, 11:05 AM
you might consider using paperless sheetrock. It's mold resistant and won't break down if it gets wet like ordinary sheetrock.
01-19-2009, 01:32 PM
My basement currently have 2x4's framed around. I just stripped off the the old wood paneling and noticed some efflorescence and some damp/wet areas on the wall. Nothing pooling or substantial.
I want to refinish the wall, and add insulation.
I was looking to clean off the efflorescence and put something on the walls to resist water (don't know what yet).
But in insulating the wall (interior), should i go with something like DOW Blue Styrofoam or anything Styrofoam, I don't want to use foam as I am a bit apprehensive either doing it myself, or the price of paying somebody to do it.
01-19-2009, 09:35 PM
Download & read the linked articles in post #7.
Short answer: yes on the blue.
01-31-2009, 04:37 PM
I have a business doing residential carpet cleaning and water damage cleanup. From my research on flood damage control the following procedures will work in most situations.
I'm currently redoing my basement due to a flood a couple years ago. My sump pump failed and ended up with 10 inches of water.
As a result of this flood and some other leaky areas in the walls I decided to gut my basement. It is an old house and the basement is in good condition. Just has some cracks where water leaked in during heavy rains and during spring snow thaws.
I'm sealing the cracks and then haveing spray foam applied. I'm leaving the stud wall approximately 1/2 inch away from the block wall. The spray foam is approved for stopping low levels of moisture. I will be sheetrocking with moisture and mold resistant sheetrock. It costs a little more but also more durable.
At the bottom of the sheetrock I am leaving about 3 inches up from the floor. This will greatly add in drying any moisture from the walls. For baseboard I will be using a commercial style plastic base which is glued on. It can easily be removed in case of a flood. With the spray foam which is water proof and sprayed onto the studds the wood will get miminum water absorption and with the water resistant sheet rock will greatly reduce the amount of drying time when it does get wet.
Short of many feet of water or sewage backup this should work well. Even with feet of water or sewage the spray foam can be cleaned off and the walls resheeetrocked. And with the foam sprayed on the sides of the studs they can be dried out in place and reused.
As for your floor I'd leave it alone. Just don't put down any kind of permanent flooring. A loose carpet that can be pulled up or large area rugs will work just fine. There are also some types of cusioned flooring out there that can be laid down where the edges snap together. They can easily be pulled up in a wet situatation, dried, cleaned and reused. Check the flooring depts of your local home improvement stores.