Frost on crawlspace walls

Red Squirrel · 01-09-2011, 10:55 PM

I have a crawlspace under my garage, it is only about 3-4 feet under ground, so it's completely in the frost zone. i occasionally go in there to clean spider webs. This is the crawlspace, before the first time I ever been in there. I have a phobia of spider webs. VERY long stick, and shop vac is used.

I noticed chunks of frost on parts of the wall. It's not exactly a straight wall and I can tell there's been lot of movement over the years. The home inspector saw that when I bought the house and said to keep it heated which I've been doing but the heater is set quite low so I may need to increase it. Keep in mind this house was built in 1965 so I think it's still in half decent condition for it's age but not as nice as the main crawlspace which only has a bit of movement and some efflorescence. Not more then that.

Now, can I safely insulate this crawlspace? Or will insulating it cause problems? I'm planing to get a company to just apply spray foam. I know the proper way to fix this problem is to probably insulate from outside, but hoping doing it from inside can be acceptable as well and wont cause the walls to freeze even more behind the foam as there will now be a lack of heat getting to them.

nap · 01-09-2011, 11:53 PM

you missed a HUGE spider in there. It's over to the right in that shadowed area way down almost to the bottom of the picture.. It looks like it is looking right at you. Must be waiting for you to crawl on by so he can jump on you.

jklingel · 01-10-2011, 12:11 AM

either those are grape vines, or you have some spiders that ought to be respected. maybe you need a 410 w/ you whilst under there??? were i u, i'd read on buildingscience.com about your options.

Red Squirrel · 01-10-2011, 02:04 AM

The spider problem is mostly taken care of now but yeah it was quite something when I first got the house.

The nice thing is because it's so cold in there they're not really active in winter, as far as I know.

Also another thing, I used non PT lumber against the wall so I can mount electrical. Do you think I may have rot/mold issues? I really should have used PT I think... the wall it's on is actually an inside wall though, so the other side is still in the house. Should be ok right? There was no frost on that wall, just a few spots on other walls, mostly corners.

jklingel · 01-10-2011, 03:13 AM

I'd have to guess on the PT wood. "The rule" is to have PT wood against any concrete that might even think about getting damp. My worry would be that "there is no dampness" but the 'crete is wicking moisture from the soil and it is evaporating at the same rate. That moisture could wet a board that reduces the airflow to the 'crete. I'd stick w/ PT anywhere that may even get "humid" and run the elect through PVC pipes nipples in the studs, or whatever you'd have to do. I have PT in my basement, and just ran the electrical like normal. I used galvanized boxes, and it has been working for 30 yrs. That said, I don't recall that I've pulled an electrical box and looked at it, either. Hmmmm.

01-09-2011, 10:55 PM	#1
Red Squirrel Wire Chewer Join Date: Jun 2009 Location: Ontario, Canada Posts: 2,975	Frost on crawlspace walls I have a crawlspace under my garage, it is only about 3-4 feet under ground, so it's completely in the frost zone. i occasionally go in there to clean spider webs. This is the crawlspace, before the first time I ever been in there. I have a phobia of spider webs. VERY long stick, and shop vac is used. I noticed chunks of frost on parts of the wall. It's not exactly a straight wall and I can tell there's been lot of movement over the years. The home inspector saw that when I bought the house and said to keep it heated which I've been doing but the heater is set quite low so I may need to increase it. Keep in mind this house was built in 1965 so I think it's still in half decent condition for it's age but not as nice as the main crawlspace which only has a bit of movement and some efflorescence. Not more then that. Now, can I safely insulate this crawlspace? Or will insulating it cause problems? I'm planing to get a company to just apply spray foam. I know the proper way to fix this problem is to probably insulate from outside, but hoping doing it from inside can be acceptable as well and wont cause the walls to freeze even more behind the foam as there will now be a lack of heat getting to them.

01-09-2011, 11:53 PM	#2
nap You talking to me? Join Date: Dec 2007 Location: sw mi Posts: 5,407	Frost on crawlspace walls you missed a HUGE spider in there. It's over to the right in that shadowed area way down almost to the bottom of the picture.. It looks like it is looking right at you. Must be waiting for you to crawl on by so he can jump on you.

01-10-2011, 12:11 AM	#3
jklingel Member Join Date: Dec 2008 Location: Fairbanks, AK Posts: 1,747	Frost on crawlspace walls either those are grape vines, or you have some spiders that ought to be respected. maybe you need a 410 w/ you whilst under there??? were i u, i'd read on buildingscience.com about your options.

01-10-2011, 02:04 AM	#4
Red Squirrel Wire Chewer Join Date: Jun 2009 Location: Ontario, Canada Posts: 2,975	Frost on crawlspace walls The spider problem is mostly taken care of now but yeah it was quite something when I first got the house. The nice thing is because it's so cold in there they're not really active in winter, as far as I know. Also another thing, I used non PT lumber against the wall so I can mount electrical. Do you think I may have rot/mold issues? I really should have used PT I think... the wall it's on is actually an inside wall though, so the other side is still in the house. Should be ok right? There was no frost on that wall, just a few spots on other walls, mostly corners. Last edited by Red Squirrel; 01-10-2011 at 02:09 AM.

01-10-2011, 03:13 AM	#5
jklingel Member Join Date: Dec 2008 Location: Fairbanks, AK Posts: 1,747	Frost on crawlspace walls I'd have to guess on the PT wood. "The rule" is to have PT wood against any concrete that might even think about getting damp. My worry would be that "there is no dampness" but the 'crete is wicking moisture from the soil and it is evaporating at the same rate. That moisture could wet a board that reduces the airflow to the 'crete. I'd stick w/ PT anywhere that may even get "humid" and run the elect through PVC pipes nipples in the studs, or whatever you'd have to do. I have PT in my basement, and just ran the electrical like normal. I used galvanized boxes, and it has been working for 30 yrs. That said, I don't recall that I've pulled an electrical box and looked at it, either. Hmmmm.

Frost on crawlspace walls