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Forum topic by SCOTSMAN posted 09-05-2013 06:37 PM 1579 views 0 times favorited 15 replies Add to Favorites Watch
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SCOTSMAN

5538 posts in 2310 days


09-05-2013 06:37 PM

Right a last chance effort to get this correct before I order the non returnable materials.
I told you earlier in last summer we built, my sons with help from the neighbours a steel galvanized shed twenty foot by ten foot (big enough for a family car.) to be used for storing precious timber etc.
Question is anyway during the cold frosty snowy nights it ended up with the roof dripping (like a shower) over everything inside.I have been told by some that it is caused by the warmer air inside coming into contact with the freezing cold metal outside and also inside too as it hits the cold turns the air vapour into water with catastophic results for me.
I intend unless told otherwise to cover the inside ( while the weather is warm) with 50mm or two inch polystyrene sheeting eight foot by four cut to correct sizing glued onto the profile with special glue.This means the warm air inside does not come in direct contact with the very cold ceiling.I guess some people tell me it will work others have reservations.Please note electricity is not inside the shed so a heater is out of the question not to say expense as heating is expensive here.Please advise as I intend to order very soon.Alistair

-- excuse my typing as I have a form of parkinsons disease


15 replies so far

View Shawn Masterson's profile

Shawn Masterson

1262 posts in 673 days


#1 posted 09-05-2013 06:55 PM

My first thought would be get prices on having it spray foamed. my concern with the foam sheets is that it may not be tight enough against the steel and you would get drips at the joints. My neighbor had the same condensation problem in his lean to. He removed the steel and sheeted the roof then papered then put the steel back down. this solved his problems. the spray foam would be a tight install sealing any leaks and I would think it would solve the condensation problem. contact an insulation company and they would know for sure.

View Joe Lyddon's profile

Joe Lyddon

7889 posts in 2777 days


#2 posted 09-05-2013 06:56 PM

Sounds good to me… BUT, I am NO Expert on the subject.

Good Luck.

-- Have Fun! Joe Lyddon - Alta Loma, CA USA - Home: http://www.WoodworkStuff.net ... My Small Gallery: http://www.ncwoodworker.net/pp/showgallery.php?ppuser=1389&cat=500"

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teejk

1215 posts in 1409 days


#3 posted 09-05-2013 07:19 PM

I was told to not use spray foam on steel…the different materials lead to different expansion/contraction rates and pockets would form that would lead to premature rusting of the steel. Keep that in mind but do consult with an insulation contractor. I personally would try to get some airflow above an insulation layer. The insulation might get damp from above but with air movement it will dry out.

View crank49's profile

crank49

3481 posts in 1696 days


#4 posted 09-05-2013 07:57 PM

The condensation has to be due to temperature difference, inside/outside, and humidity inside.

Question-1, why was the interior warm if it was not heated?

Question-2, if it is not heated anyway, would you mind ventilating it. Might avoid the need for insulation.

It might be a good idea to spray some of that expanding “foam from a can” into the joints.

With a non-heated interior, and with 2” of polystyrene foam and sealed joints that should handle it.

-- Michael :-{| “If you tell a big enough lie and tell it frequently enough, it will be believed.” ― A H

View JonJ's profile

JonJ

163 posts in 2565 days


#5 posted 09-05-2013 08:23 PM

It may be mentioned, but I missed it if so. What type of floor is it? If it is dirt/gravel or concrete without vapor barrier, that could be where most of the moisture is coming from. If you have concrete, and don’t know if there is a vapor barrier, a simple test is to lay something on the floor overnight (like a rubber floor mat) and see if is dark (damp) underneath the next morning. The floor would not be the sole source of the problem, but it can make a lot of moisture, and needs to be addressed in addition to insulating metal.

-- Jon

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Tugboater78

1225 posts in 917 days


#6 posted 09-05-2013 08:28 PM

That sheeting with a gap between it and the steel roof should fix your problem granted the eaves are opentallow air movement. I am no expert either but what little knowledge I do have, tells me this. Ther roof is “sweating” and if it is allowed a chance to “breath” the condensation should be minimal or eliminated.

-- Justin - the tugboat woodworker - " nothing changed me like the first shnick from a well sharpened, decent hand plane"

View Porchfish's profile

Porchfish

579 posts in 1257 days


#7 posted 09-05-2013 10:15 PM

Jon J makes an important point that we all should have thought of Alistair. I think you are on the right track with the addition of 2” of insulating foam and that should provide your solution, as long as the flooring is taken into consideration. Concrete floors can be sealed relatively inexpensively. this solution would work here in our North Florida Region, an insulation specialist for your snowy region should be consulted for his opinion on your approach. P.S. If the side walls are left uninsulated they will also collect condensation for the same reason the ceiling did. Here your insulation specialist for your climate would be able to give you the best advice. Best of luck Alistair ! Take care of yourself too ! Your North Florida friend, Don S.

-- If it smells good, eat it ! The pig caught under the fence is the one doing all thesquealing

View danoaz's profile

danoaz

178 posts in 895 days


#8 posted 09-06-2013 12:00 AM

@Scotsman – As an architect, I can mention some things and you can decide for yourself if it makes sense. The cause and affect is correct in your description. I am guessing that the roof is a corrugated metal with some sort of metal framing? Attaching the polystyrene will help but you will want to tape all the seams to prevent the warmer air from seeping up and causing other problems like rust or moisture degrading the glue over time. Ideally you would want to do that on the walls as well to make a sealed envelope inside, but you have to be aware of not trapping the moisture in the walls even if you seal it well. It gets a little hard to describe here, but you need some vent holes at the bottom and so I am not sure how the walls come down on to a slab maybe ? Going back to the roof, the air flow between the poly and the flutes of the metal roof should remain free or open to keep air circulating there as well. Another challenge is with the roof framing and how to deal with those areas. Maybe if you can describe it better or send a picture that would help. I hope I haven’t confused you.

-- "Simplicity and repose are the qualities that measure the true value of any work of art." Frank LLoyd Wright

View PASs's profile

PASs

571 posts in 1823 days


#9 posted 09-06-2013 12:20 AM

Alistair,
Watch this video.
Poor Man's Spray Foam
I intend to do this in my attic (to create a thermal break) and in the walls and ceiling of my shop.

-- Pete, "It isn't broken, you just aren't using it right."

View TopamaxSurvivor's profile

TopamaxSurvivor

15030 posts in 2401 days


#10 posted 09-06-2013 01:53 AM

No expert, but I have seen a this fiber glass insulation with some type of cloth looking material backing stop the drips. All you need to do is keep the moisture filled air from touching the cold metal.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View mastersus's profile

mastersus

13 posts in 469 days


#11 posted 09-12-2013 09:12 PM

Hi Scotsman, fellow Scot putting his oar in, polythene bubble wrap (thicker the better) fixed on the corrugations/profile with spray adhesive or carpet layers double sided tape, spay on might be easier for you, here’s a link for you on the glue – http://www.tesco.com/direct/spray-adhesive/610-7659.prd?pageLevel=&skuId=610-7659&kpid=610-7659&gclid=CNjN8OjhxrkCFXMbtAodVRwAQw and the bubblewrap (unless you someone who can get it for you easily) – http://www.kitepackaging.co.uk/scp/bubble-wrap/large-bubble-wrap/ ...lang may your lum reek…mastersus

-- AL, frae bonny Scotland

View Jim Finn's profile

Jim Finn

1733 posts in 1647 days


#12 posted 09-13-2013 12:38 PM

Would just leaving the door open, so that there is no temperature difference between outside and inside, work? I would try that first.

-- In God We Trust

View PASs's profile

PASs

571 posts in 1823 days


#13 posted 09-13-2013 12:49 PM

Alistair,
Along the line of Jim’s reply, if you’re just worried about condensation and not temperature, why not ventilate the shed. I put a couple of louvered vents in my sheet metal garden / wood storage shed. They even have screening built in.

-- Pete, "It isn't broken, you just aren't using it right."

View stefang's profile

stefang

13530 posts in 2059 days


#14 posted 09-13-2013 04:58 PM

Polystyrene is highly flammable and it makes poisonous gas when burning. Maybe not a issue in your storage shed. Here in Norway we always seal insulation with plastic sheeting on the inside of the insulation as a moisture barrier between the inside of the shed and the insulation or whatever is on the outside of it, similar to what Danoaz said. I assume the moisture is coming from storing wet wood that is drying out, and that being the case some ventilation would be desirable as PASs said. Both good suggestions.

-- Mike, an American living in Norway.

View Gary's profile

Gary

7534 posts in 2158 days


#15 posted 09-25-2013 11:27 AM

Alistair, did you get your problem solved?

-- Gary, DeKalb Texas only 4 miles from the mill

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