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WILL1E
Moderator
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# Posted: 4 Jan 2022 08:50 - Edited by: WILL1E
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My cabin floor is elevated off the ground 2-3'. After i built the main beams, installed all the floor joists and rim boards and decked it, i stood the walls up (2x6's). I then skirted the treated 2x10 rimboards with 14" wide aluminum to give it a finished look on the exterior as well as some protection. I then installed the plywood sheathing.
As I was doing some work in the cabin this weekend and had the pellet stove going, i noticed this.
The outside temp was in the mid teens (Fahrenheit) during the day and single digits or possibly colder overnight. I have zero insulation in the cabin at this point and obviously no vapor barriers yet. If i had to guess it was maybe low 30's on the first floor and maybe 40ish in the loft. Air is obviously leaking in between the sheathing, the aluminum skirting and the rim board and bottom plate.
Is the frosting only happening because the walls cavities are open right now and i'm heating the place? Will this be a concern once i have insulation in there and a vapor barrier up?
I'm weeks, or realistically months, away from being ready to insulate but wondering if i need to do something to stop this from being a bigger problem later. I was thinking about putting a bead of caulk along the bottom of the sheathing outside to prevent air from going up between it and the aluminum. Then i was thinking spray foaming the along the bottom of the wall cavity inside to basically cover up that aluminum you can see on the inside.
Thoughts?
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curious
Member
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# Posted: 4 Jan 2022 09:06
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A smaller picture would be nice as that would make it easier to read the text. Maybe use the site's upload feature to display the image.
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curious
Member
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# Posted: 4 Jan 2022 09:08
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Thank you
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WILL1E
Moderator
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# Posted: 4 Jan 2022 09:11
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Sorry, imgur wasn't being nice to me this morning 
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curious
Member
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# Posted: 4 Jan 2022 09:18
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I don't quite understand what the picture is showing,
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curious
Member
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# Posted: 4 Jan 2022 09:25
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Oh, is the plywood on the exterior overlapping the sheet metal band and the plywood is nailed to the bottom plate and studs?
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jhp
Member
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# Posted: 4 Jan 2022 09:32 - Edited by: jhp
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I don't think the problem is the air can get to it through the crack, the whole piece of flashing is just much colder than the inside air temp. Even if you caulked it, this would still happen.
If you're heating with something like a buddy heater that puts out a lot of moisture the problem is just compounding...what you're seeing is the cold beer can effect backwards. Hot outside, cold inside, metal surfaces condenses moisture in the air.
That being said I don't think you have this problem anymore once you have insulation and a vapor barrier, assuming that you have something inside exchanging the air faster than it can seep through the cracks in the walls. The flashing will still be cold but the vapor barrier should stop the majority of the moisture from getting that far.
Meaning if you have forced air, or a vented stove of some type you'll be pushing out the warm moist air out through that faster than it can find its way out through a wall.
I think I'd caulk the gap anyway and then not worry about it. Don't insulate until its warmer outside and you are sure the moisture is gone so you don't trap it behind the wall.
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WILL1E
Moderator
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# Posted: 4 Jan 2022 09:38
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So the photo is from inside of the cabin.
Yes, the plywood is nailed over the aluminum. I added an illustration to show a cross section of what you are looking at.
The sheathing covers all of the studs and maybe about 1" of the rim board. The aluminum Hangs about 1" below the rim board and covers all of the rim board, all of the bottom plate and ends about 2" above the bottom plate....which is what you see in the photo above with the frost on it.
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Steve_S
Member
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# Posted: 4 Jan 2022 10:03
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The aluminum is a heat sink and will always attract any moisture when there is a temp differential. Even when you have insulation in place, it will pull whatever it can from it. Spray foam "may" cancel that out due to the direct contact & adhesion but I don't know.
You mentioned Pressure Treated & Aluminum, I really hope that the metal is completely isolated from PT wood or nasty things will start in short order. Makes a mess out of aluminum in a couple of years.
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WILL1E
Moderator
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# Posted: 4 Jan 2022 11:26
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Quoting: Steve_S I really hope that the metal is completely isolated from PT wood
It is factory painted on both sides.
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travellerw
Member
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# Posted: 4 Jan 2022 11:45
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If you do full vapour barrier, then I don’t think this will be an issue. The vapour barrier will stop the warm moist air from entering the wall cavity. I would pay close attention to sealing up any outlets though to ensure no leakage.
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Brettny
Member
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# Posted: 4 Jan 2022 11:59
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The reason why you see this is because you heated the place. Warm moist air is hitting a cold metal object. Same as a glass of cold water on a hot summer day.
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NorthRick
Member
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# Posted: 5 Jan 2022 18:03
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Quoting: Brettny The reason why you see this is because you heated the place. Warm moist air is hitting a cold metal object. Same as a glass of cold water on a hot summer day.
This. The aluminum is cold and non-porous. There is moisture in the heated indoor air from your body, cooking, doing dishes, and anything else involving water. That moisture is condensing on the aluminum and then freezing.
I wouldn't worry about it if it is short term (couple of months of cold weather). When the time comes to insulate and install the vapor barrier, do a good job on both and your cabin will be fine.
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toyota_mdt_tech
Member
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# Posted: 5 Jan 2022 21:33
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Willie, should of just bought the longer siding, it would of tied the walls to the floor better. OK, about some closed cell spray foam over the metal, problem solved or some spray on stuff like that "flex seal" over the metal in the stud wall area.
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Steve961
Member
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# Posted: 5 Jan 2022 23:10
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Quoting: toyota_mdt_tech OK, about some closed cell spray foam over the metal, problem solved
This right here. My entire cabin shell is metal (3 shipping containers) and closed cell spray foam is the only thing I would trust to both insulate and be a vapor barrier.
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WILL1E
Moderator
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# Posted: 6 Jan 2022 08:02
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Quoting: toyota_mdt_tech should of just bought the longer siding
I did not want the siding/sheathing to cover the entire rim joist for 2 reasons. One being that on the entry door side there will eventually be a deck and i'll want that deck as level with the entry door threshold as possible. Secondly, i suspect someday i'll skirt the place to keep the cold air from blowing under the cabin. Having the rim joist exposed but yet covered with the aluminum will give me a good backer for mounting the skirting.
Quoting: toyota_mdt_tech closed cell spray foam over the metal
Yeah, i think i'll get a couple cans and and spray the inside just enough to cover the gap between the bottom plate, all of the skirting metal you can see in the stud bay and then end it just above where the metal ends.
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travellerw
Member
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# Posted: 6 Jan 2022 10:04
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Quoting: WILL1E eah, i think i'll get a couple cans and and spray the inside just enough to cover the gap between the bottom plate, all of the skirting metal you can see in the stud bay and then end it just above where the metal ends.
I'm guessing you are going to be using a bunch of foam in the future (this, around the windows and doors, other gaps,ect)... For me it actually paid back to buy a foam gun on Amazon and then use large industrial cans. Just a thought.
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BRADISH
Member
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# Posted: 6 Jan 2022 11:12
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I am no expert, but I think this problem goes away when you insulate and vapor barrier properly.
Right now you have warm moist warm hitting a cold wall. That temp differential goes down substantially once you insulate, and the moisture differential will go down to nearly zero once you put up the VB.
You will then only have the differential between the outside of the plywood and the house side of the plywood which is minimal.
I think what you're seeing is just an effect of building in progress.
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gcrank1
Member
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# Posted: 6 Jan 2022 12:25
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Ive been in travel and house trailers here in WI that folks have lived in over-winter that have had frost 3' up the walls.
Many would stack straw bales outside against the trailer (back when they were cheap) up that high the second winter.
I read about one fellow in Europe? that stacked bales all around and over his caravan, think he draped a tarp over the top of that. Looked just like a hay bale stack.
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NorthRick
Member
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# Posted: 6 Jan 2022 13:14
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Quoting: WILL1E Yeah, i think i'll get a couple cans and and spray the inside just enough to cover the gap between the bottom plate, all of the skirting metal you can see in the stud bay and then end it just above where the metal ends.
Keep in mind that stuff is temperature sensitive. Spray it on cold frosty metal and it isn't going stick or expand properly.
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WILL1E
Moderator
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# Posted: 6 Jan 2022 13:27
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Quoting: travellerw I'm guessing you are going to be using a bunch of foam in the future (this, around the windows and doors, other gaps,ect)... For me it actually paid back to buy a foam gun on Amazon and then use large industrial cans. Just a thought.
My windows are already done. But i did buy one of these guns for doing the roof. Unfortunately the great stuff cans didn't fit it for some reason. So i need to find one that does fit.
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Nate R
Member
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# Posted: 6 Jan 2022 13:34
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I think you have to use the "pro" version of the great stuff cans that don't come with a straw and are larger.....Available at HD, IIRC.
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travellerw
Member
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# Posted: 6 Jan 2022 13:41
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Quoting: Nate R I think you have to use the "pro" version of the great stuff cans that don't come with a straw and are larger.....Available at HD, IIRC.
Yup.. That is correct.. There is only one standard for the guns, so unless that gun was faulty a "pro" screw on can should have fit!
The gun is WAY WAY better than the cans with a straw. Way more control and you can dispense exactly what you need.
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Brettny
Member
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# Posted: 6 Jan 2022 16:49
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I looked into the pro gun for canned foam. It costs more than the non pro stuff and I have to clean a gun when I'm done.
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WILL1E
Moderator
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# Posted: 7 Jan 2022 08:05
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Quoting: Nate R I think you have to use the "pro" version of the great stuff cans that don't come with a straw and are larger.....Available at HD, IIRC.
Never knew there was "pro" stuff, just assumed the next level up was the big fancy kits that everyone talks about on here. I'll have to look and find the pro stuff. Do they keep it in the same area as the straw canned stuff?
Quoting: Brettny I looked into the pro gun for canned foam. It costs more than the non pro stuff and I have to clean a gun when I'm done.
Well you can leave the can on for 30 days as long as you close the nozzle after you are done. They sell the can of cleaner, since i haven't used the gun yet i'm not sure how much it uses per cleaning.
Does anyone know if they make an attachment that cause it to spray out more like a fan vs. a bead?
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Nate R
Member
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# Posted: 7 Jan 2022 08:38
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Yeah, I've heard mixed reviews on the Pro stuff and gun for people who aren't using it every day..... I've stuck to the straw cans, so far.
https://www.homedepot.com/p/GREAT-STUFF-PRO-24-oz-Gaps-and-Cracks-Insulating-Foam-Sea lant-341557/202892471?
This stuff is made for the guns, I believe. I've seen it in various locations at different HDs.....sometimes by the straw can stuff, sometimes not.
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travellerw
Member
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# Posted: 7 Jan 2022 11:29 - Edited by: travellerw
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Quoting: Nate R Yeah, I've heard mixed reviews on the Pro stuff and gun for people who aren't using it every day..... I've stuck to the straw cans, so far.
I bought my cans from a builder supply and they turned out about %25 cheaper and you got more foam. However it might be a wash once you factor in the cleaner.
To me, it was just a better solution. More control, less mess and easier to use. You don't have to clean it every time, only if you are leaving it for more than 2 days or so. There is a ball bearing that seals up the wand when not in use.
It also let me build my stairs with the Great Stuff Pro Construction adhesive instead of PL based glue. Everyone says it a much better bond than PL.. I guess time will tell, but it was interesting to work with and sure seemed to stick REALLY well.
I had terrible experiences with new straw on the Great-Stuff cans. I had one break, then the second one leaked all over my hands.
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