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optimistic
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# Posted: 25 Nov 2013 08:49am
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My cabin was a prefab shed I am converting into a cabin. 12x12 with 13ft ceilings. The walls are built from 2x4s 16oc. Then there is a 1/2" wood panel material that is made of two wood types: a plywood sheet that is glued/attached to a weather treated wood sheet - that faces the outside and acts as siding.... I can't explain it any better but if it is critical I can probably find exactly what it is from the company that made me the shed.
Then I have 2x6 floor joists that sits on five 4x4 skids... Classic shed construction.
My cabin is about 75% insulated but no vapor barrier yet or wall finish (almost anywhere). I don't have a shower, kitchen, or bathroom installed yet.
Yesterday, I noticed water accumulating in a corner where the 2x4 wall studs meet the bottom/sill plate and the plywood sheathing... When I touched the sheathing it felt wet.. almost soaking wet. I then touched the same spot on different walls (where the sill plate and sheathing meet) and they were all wet... Where the hell is water coming in from? I have gutters, metal roof overhang, and the walls seems to be water tights. There is no snow on the ground.
Also, I didn't want to pull out insulation where it was installed but I was able to stick my hand beyond a place with insulation - and it felt dry... but I just checked in one spot.
I am attaching photos of where this was but obviously it happens basically every place the sill plates and sheathing meet - I just didn't think it is necessary to have 20 photos of the same thing. I am worried this will rot my cabin and I really have no idea where this could be coming from beside condensation... I am hoping you guys will agree and tell me that once I insulate I will be home free..
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MtnDon
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# Posted: 25 Nov 2013 10:02am
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Sounds like condensation. Was it there when you arrived? Or only after the cabin had been occupied a while with prople inside? Cooking food, boiling water? What was the source of heating?
The perimeter down low will be the coldest spot even with a fire going. Chances are good that with insulation and a vapor barrier (6 mil poly) you will not have that problem.
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SE Ohio
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# Posted: 25 Nov 2013 10:11am - Edited by: SE Ohio
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Going out on a limb here... If the plywood was very cold and a non-vented propane appliance was being used, I have a hypothesis. Since heat rises, the bottom of the wall is much colder than the top. Extra moisture from propane or other combustion (and human exhalation) condensed on the lower colder areas. Could this be the case? If so you might have noticed the extra humidity. Insulated walls would prevent this in the future.
Exposed metal roofs are even worse for condensation. I've read of folks getting "rain" indoors!
If the exterior isn't sealed enough, it may be possible for exterior water (rain) to wick through, especially up the exposed bottom of the sheeting. Recent heavy rain?
After that, I'm outta ideas! Good luck.
(edit - I see Mtn Don wrote a response as I wrote... I'll have to get up earlier next time)
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optimistic
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# Posted: 25 Nov 2013 10:21am
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Don -
I didn't notice it or checked when I arrived but only after we spent the night there already... I will check it when we first get these this weekend. No cooking food, no appliances are in the cabin, and no boiling water... source of heating is the wood burning stove that has an air intake from the outside.
SE ohio - no propane appliance or any appliance is present in my cabin. wood burning stove provides the heat. I hope this is indeed condensation and that insulation will solve this.
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Dillio187
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# Posted: 25 Nov 2013 12:08pm
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the seam between the sheeting and the framing is likely leaking cold air, causing condensation much like a leaky window. Seal the seam between the framing and the sheeting and it will help out, as well as a proper vapor barrier as the others have mentioned.
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toyota_mdt_tech
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# Posted: 25 Nov 2013 12:34pm
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Condensation is what it sounds like. If there is a large temp difference from inside to outside, can happen also. Very humid plus temp difference from inside vs outside. Good ventilation and insulation with good vapor barriers helps a lot. Do you have a water tight (non breathable) vapor barrier on the ground below the cabin? This should be a black (no UV penetration) type.
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Martian
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# Posted: 25 Nov 2013 01:26pm
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Besides the tips you've received above, try using a small fan to circulate the air. I imagine there is some striation of the warm/cold air down close to the floor.
Tom
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Truecabin
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# Posted: 25 Nov 2013 01:48pm
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no power no fan
same as a cold beer does in a warm room that has humid air from lots of people breathing
after you insulate your wall will be warm now and it wont get wet
your vapor barrier will stop the mosture from getting to the cold siding
everythings the same inside except tha wall is warm so it wont take the water out of the air
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optimistic
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# Posted: 25 Nov 2013 02:00pm
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Thank you so much everyone!
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PA_Bound
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# Posted: 25 Nov 2013 02:22pm
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How about the same area on the outside of the wall? In particular, the cut edge. Are they wet or dry?
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rayyy
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# Posted: 25 Nov 2013 05:07pm
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When it drop's below freezing,moisture trapped inside will condensate onto the colder surfaces inside your cabin.That includes wood,glass,metal or any surface that get's cold.Your insulation and vaper barrier arn't in these areas as of yet.Moisture will gather there.Once you insulate and vaper barrier are in,that moister will collect somewhere else inside like your windows and doors,even the metal screws or nails holding your ceiling up will produce moisture.Especially if your burning propane inside for heat.Your always going to have lot's of moister to deal with.A through the wall vented heater is best for this.Unvented propane heaters give off a lot of moisture and it will show up in the stranges places.
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optimistic
Member
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# Posted: 25 Nov 2013 05:50pm
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PA- I didn't touch the outside but I am guessing not... Didn't look wet
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Martian
Member
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# Posted: 25 Nov 2013 06:52pm - Edited by: Martian
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I can tell you from personal experience, even if the wall is insulated, you are going to get moisture about 2" above the floor, unless you keep the air moving. Also, there will be moisture behind any furniture or box you put against the wall.
I have 2X4 walls in both my cabins. They are insulated. If the ceiling fan is off, and its really cold, below 25F for awhile, then those places I listed above, condensate. The floor in one is insulated, but the other, which has a wood stove, is not. The wood stove helps a lot, but there is still a slight dampness at the bottom plate. Wood framing passes the cold eventually; so even if you spray in foam, you may still have condensation. Just not as quickly. 
If you operate on 12vdc, then I'd suggest a small 12vdc fan to circulate the air.
Tom
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tcmatt
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# Posted: 25 Nov 2013 08:36pm
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It doesn't look like there is any airflow/circualtion of air under the cabin. Does anyone think that might be the cause? Moisture from below?
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PA_Bound
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# Posted: 25 Nov 2013 09:23pm
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One more question, how cold was it outside when you noticed this?
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rockies
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# Posted: 25 Nov 2013 09:46pm
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Unfortunately batt insulation and a vapour barrier won't stop the condensation from appearing on the inside of the outer wall sheathing. Even with batt insulation installed, the material is porous, so there is always a convection draft occuring in the wall cavity as the warmer air next to the interior wall finish will rise and the air next to the colder exterior sheathing falls. Any vapour that gets in from the tiniest hole (from either outside or inside) will stick to the coldest surface and eventually cause mold or rot. The best thing to do is raise the temperature of the exterior sheathing surface, either with a "closed cell" spray on insulation (Tiger Foam makes a kit for DIYers) or wrapping the exterior with two thin layers of rigid insulation and offsetting and taping the seams. This article on the buildingscience.com website might help. There are a lot of others on insulation, vapour barriers, etc. as well
http://www.buildingscience.com/documents/insights/bsi-049-confusion-about-diffusion/? searchterm=dew point
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toyota_mdt_tech
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# Posted: 27 Nov 2013 10:37am
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To keep air moving while you are away and temp the same inside vs outside to reduce tyhis condensation, could you install large vents at each end on the gables and then when away, have an inside shudder to oepn them up, then when there with heat, have them closed?
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optimistic
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# Posted: 27 Nov 2013 02:03pm
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PA- about 20....
rockies- I thought about doing that - putting sheets of rigid foam on the outside. I planed on doing live edge boards anyway on top of what I have now... Next year.
toyota- how about leaving some windows a bit open? will that work?
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silverwaterlady
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# Posted: 27 Nov 2013 04:03pm - Edited by: silverwaterlady
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I recall that the ground you built on is not well drained. Muddy and wet. Could it be the wood is acting as a wick and sucking up the water?
Building six inches off the ground could have elimated a lot of issues.
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PA_Bound
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# Posted: 27 Nov 2013 04:54pm
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SWLady... That's similar to what I was thinking, and why I earlier asked if the bottom edge of that exterior panel was wet (Opti indicated he didn't think so). That first picture show a fair amount of water, and I was thinking that if it was inside humidity it would be higher on the board and running down, not low and seemingly wicking up. But I could see how that could happen if cold air was being blown from the outside, under that panel, and up into that area. But as warm, humid air typically rises, to be that wet, that low, I would think the iternal air would have to almost tropical.
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neb
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# Posted: 28 Nov 2013 10:04am
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Quoting: Martian I can tell you from personal experience, even if the wall is insulated, you are going to get moisture about 2" above the floor, unless you keep the air moving. Also, there will be moisture behind any furniture or box you put against the wall.
Yes I agree!
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optimistic
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# Posted: 28 Nov 2013 03:37pm
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The ground I built on was not so muddy and there is no way it is wicking...the stones and soil around is very dry. Also it sits on 4x4 which makes it even higher.
I was just thinking about, in order to add insulation under the cabin,to lift the cabin and slide 6x6s under the 4x4s..
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MtnDon
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# Posted: 28 Nov 2013 04:10pm
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Quoting: neb Quoting: Martian I can tell you from personal experience, even if the wall is insulated, you are going to get moisture about 2" above the floor, unless you keep the air moving. Also, there will be moisture behind any furniture or box you put against the wall. Yes I agree!
I believe that depends. If the insulation is done right along with getting the air sealing done right there is no need to have interior condensation. At least that is the case with our mountain cabin. YMMV.
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toyota_mdt_tech
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# Posted: 28 Nov 2013 05:59pm
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Quoting: optimistic oyota- how about leaving some windows a bit open? will that work?
Yes, it would do the same as gable vents, I was just thinking of security reasons. You could build wooden covers to cover your windows, then install a metal vent in the top of the window cover and leave the window open partially, this would give you some security and ventilation also.
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optimistic
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# Posted: 28 Nov 2013 06:58pm
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The ground I built on was not so muddy and there is no way it is wicking...the stones and soil around is very dry. Also it sits on 4x4 which makes it even higher.
I was just thinking about, in order to add insulation under the cabin,to lift the cabin and slide 6x6s under the 4x4s.. Maybe a summer project.
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optimistic
Member
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# Posted: 2 Dec 2013 02:58pm
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I touched the walls as soon as I walked in last weekend... they were dry. so like many have you speculated: it is condensation.
I am almost finished with the insulation so it won't happen anymore.
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creeky
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# Posted: 3 Dec 2013 06:59pm
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Optimistic. It was interesting that the water appeared right where you have cables coming through the wall. So a wind driven rain event.
cough*caulking*cough.
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Redneck7
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# Posted: 4 Dec 2013 12:33am
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From what I am gathering I think it's because te inside is totally sealed. You should try gable end vents so that moisture can escape. Or a roof vent of any sort. If your worried about heat loss, try a source of meh animal ventilation. I'm not sure what those can cost but I don't see much heat loss through your size cabin. Also depending on your wind directions you can install it so the winds don't suck your heat out. Something to consider.
Kyle
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bukhntr
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# Posted: 21 Dec 2013 03:44pm
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I am betting it is just the small gap where the siding is attached to the bottom plate and the moisture you see is from the air exchange difference between inside and out before it evens out to inside air temp. The same way you see frost form above the seam of the sashes in old windows. We have a similar build cabin and did not notice this but I'm guessing if you put a heavy bead of caulk under the bottom edge of siding it will prevent this. After seeing your pics I am going to do this at our cabin this spring
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