DIY Chatroom Home Improvement Forum

DIY Chatroom Home Improvement Forum (
-   Insulation (
-   -   Should I put new insulation in the basement? (

word2yamutha 04-19-2013 02:43 PM

Should I put new insulation in the basement?
2 Attachment(s)
They did a poor job insulated the basement from what I can tell. Some of the insulation has mold on it and I think they might be a reason for some bug issues in the basement. I'm not sure if this type of insulation is suppose to be stapled in or what not, but it can be easily pulled out by hand.

I was going to buy some of this

I went ahead and measured it out and I need about 5 rolls of this. I thought about cleaning behind the old insulation if this is ok? What is the proper way to install insulation?

joecaption 04-19-2013 05:12 PM

It's moldy because no one foam sealed the gaps and used styrofoam to finish sealing up that area.

word2yamutha 04-19-2013 05:26 PM

Do you recommend a certain product?

joecaption 04-19-2013 05:31 PM

Great Stuff and 2" thick blue foam you can get at any box store.

word2yamutha 04-19-2013 06:07 PM

So put up the 2" foam board first then the batting?

joecaption 04-19-2013 06:13 PM

There has to be hundreds of post on this exact subject under insulation.
Just go to the search funtion.

word2yamutha 04-19-2013 06:23 PM

I mostly get insulation for basement walls results. I just didn't know how to properly insulate because we are leaving the basement unfinished.

Gary in WA 04-20-2013 12:09 AM

You can DIY SPF or use rigid foamboard/canned foam, as Joe said.
Also, caulk the mudsill/concrete gap against air ifliltration/exfiltration as this may be the source of the moisture in the air condensing on the wood. If there is a poly sill sealer under the p.t. plate, you have a water problem elsewhere as the bottom of the I-joists should not be wet. Another picture of the outside wall at siding level about 6' away would help. It may be the siding drip edge doesn't go below the mudsill and more flashing is required.


gregzoll 04-20-2013 12:49 AM


Originally Posted by joecaption (Post 1162954)
It's moldy because no one foam sealed the gaps and used styrofoam to finish sealing up that area.

If it was mold or mildew, it was due to because water or moisture got between the insulation and the OSB, due to temperature differences between the cold side and the warm side of the insulation.

I have Batts around my basement Sill & Joist bays, and do not have a issue with mold or mildew. Only place that I have ever gotten it, was under the tub, due to water got between the tub surround that we installed, and the tub, due to a gap, from the tub being not even along the wall, to begin with, from when they put it in back when the house was built in 1937.

Gary in WA 04-20-2013 11:26 AM

Your bottom of the sub-floor looks similar to this current one;

No sill-sealer = moisture;

I agree with Joe, stop the air leaks, use f.b. not f.g. at the rims;


word2yamutha 04-20-2013 02:07 PM

2 Attachment(s)
Does it matter what kind of caulk I use for the mudsill? I went ahead and uploaded the other picture because it looks like this is only a problem from the front of the house(the concrete wall pictured is the front of the house). The other concrete walls don't look like this.

Didn't know the foam board was going to be so expensive. I was checking out this one

so after I caulk I should put this up?

Would it be cheaper to use can foam? If so, is there a brand you guys recommend? Thanks for the help so far guys, much appreciated.

Gary in WA 04-20-2013 03:01 PM

At better picture, you don't need the sill-sealer, it is already in place. All the moisture streaks on concrete are a clue...

The rim joist area is similar to a wall; distance/depth of cavity insulation from the heat source to the foamboard; Notice, the more cavity insulation= the thicker f.b. required to prevent condensation on the inside the f.b. There will be no condensation on the rim as it is air/moisture sealed from basement air. I'd go with the higher thickness listed for 2x6 wall, to compensate finished drywall in the basement later. I could figure the dew-point, if I had your largest closest city name... below the map; if in Zone 4, or Zone 5;

PS. Is there brick veneer on the other side of rim?

word2yamutha 04-20-2013 03:43 PM

no brick veneer on the outside. I live in zone 4 about 40min away from columbia, MO. So the wet looking part on the concrete is the sill seal correct? So go ahead and caulk where the wood meets the concrete?

So when installing the foam board it doesn't touch the concrete part, correct?

gregzoll 04-20-2013 04:50 PM

If all they used was that foam stripping between the framing and the concrete, that right there is why you are getting moisture pulling into the house from the outside. You have to love how homes are built these days, compared to back in the day, when they were built to last.

You are lucky if homes built these days to last more than 10 years, before they start falling apart.

Gary in WA 04-21-2013 02:03 PM

Sill sealers are designed to stop air/moisture/low water absorption/insects. It is the best you can have, and you have it;

I am concerned you have a water source at the mudsill, wetting the joist bottoms as pictured. They should be dry. Your exterior flashing/housewrap is defective there. What type of siding---- a picture of outside house would help- 8' away...

you may be able to remove a bottom course and add sill flashing there;


All times are GMT -5. The time now is 02:24 PM.

vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.

Search Engine Friendly URLs by vBSEO 3.6.1