# inside leaking roof on my new woodshed all steel construction?



## SCOTSMAN (Aug 1, 2008)

I have the most awful condensation dripping from the roof of my new all steel workshop storage shed.I have been told that applying a few thin rolls of polystyrene insulation material will stop it how thick does it have to be any other information wood be most helpful too? I am sure it's not a leak as the whole roof inside is dripping.Alistair


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## chrisstef (Mar 3, 2010)

I wonder if a small dehumidifier would help out Alistair? In terms of the pS insulation i cant imagine anythign over 1" would be needed.

Were the roof seams welded? Maybe they burnt through a small portion?

Just tossing ideas around.


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## MrRon (Jul 9, 2009)

A spray-on insulation applied to the roof might work; the type used on mobile homes. Condensation is due to warm moist air striking a cold surface.


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## Chipncut (Aug 18, 2006)

*I had a friend who built a ice fishing dark house for spearing fish out of aluminum sheets.

When he lit his small heater, condensation would build up, & freeze it would melt, & drip off of the sheeting.*


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## Built2Last (Nov 17, 2008)

This is the reason they build most storage building out of aluminum, it doesn't do that. With steel, you would have to keep it bone dry, so I don't think a dehumidifier would help. If it got the humidity low eoungh to stop the condensation, you lumber may get to dry. You best soulution, is to put fiberglass insulation on the top, preferebly the kind with a plastic backing like they use on Butler type buildings. I built an 80 by 88 shop with steel roofing and had the same problem, " like a rain forest up in there". You can also spray the foam type but here its hard to find someone to spray a small building. Good luck!!


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## donwilwol (May 16, 2011)

It needs to be thick enough to keep the warmer moist air from making contact with the metal. I would suggest talking to someone who knows your climate conditions for what you need.

I think mrron is on the money but don't know how thick it should be.


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## teejk (Jan 19, 2011)

condensation issue. I was told NOT to spray foam since the steel and material expand/contract at different rates leading to pockets of moisture that will cause a premature failure of the steel. cut in gable end vents to start (warm air seeks cold air). an industrial ceiling fan (pretty cheap) would help also I think.


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## patron (Apr 2, 2009)

most old tin roofs just laid the tin on cross stringers

would rot the top of the wall plates and stringers
from the condensation thru the metal

the way to stop it 
is why they put tar paper 
under the metal
so the water goes out
without catching on the stringers or wall plates

like a sub-roof for the water

many old barns were so open 
that it wasn't a problem


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## donwilwol (May 16, 2011)

When I built my shop I was told to plywood the roof instead of using strapping because it would prevent condensation. Its worked so far.


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## HorizontalMike (Jun 3, 2010)

I'm sorry to hear that Scotsman. Is it too late to add a roof vent? On my metal shop I have an 8ft long vent along the gable. It has a chain pull to open and close the vent from the inside. Just a thought.

Similar to one of these:


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## renners (Apr 9, 2010)

Any chance you could post a photo Alistair?

There's a number of things you could do, but without knowing the construction it difficult to know where to start.

Also, would you be able to take the roof off in the spring or are you trying to avoid that?


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## teejk (Jan 19, 2011)

was thinking the same thing Renners…without knowing the structure it's hard to make suggestions. Cheapest solutions though would be to get the warm moist air outside (warm air moves to cold air) via gable vents or drive it back down via fan(s).

surprised he doesn't have a ridge vent on the top (pretty much code now I think)...I have it in my steel building along with ventilated sofitts that creates an automatic air flow.


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## juniorjock (Feb 3, 2008)

Lots of good stuff here. I've had the same problem. Cold meets heat = condensation. I installed some R13 insulation and I think that has taken care of it. I do pull it out in a couple of places to check it every now and then. Just wondering if a vapor barrier would help or would that be worse because its on the paper side of the insulation??


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## HorizontalMike (Jun 3, 2010)

JJ,
You may be on to something there. Insulation will sure help minimize temperature fluctuations inside, but one still needs to vent air on those days of extreme variation. I think I am using something called Solartex, or the like, on my shop. It is only 1/4in thick, has a vapor barrier, a radiant heat barrier, and 1/4in of fiberglass insulation. In south Texas this is perfect! In the middle of winter I can heat my 24×30 shop with a single 1000w baseboard heater. I get up to mid-60s within a couple of hours.


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## DrDirt (Feb 26, 2008)

Good Points, I have seen best results on metal buildings (Morton is the big company here in Kansas) but there are others, is to go with the spray on foam, as there no water trapped anywhere.

Allistair didn't mention what he was using for heating. If it is kerosene or Propane, there is a lot of water there. So an option depending on how warm you like it, and the kwHr rate for electricity is to use an electric heater.


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## SASmith (Mar 22, 2010)

Around here most pole barns have something like this to prevent condensation. It is less than a half inch thick. Not sure of the R factor (low I'm sure) but it does prevent condensation.

It is typically installed between the purlins and the roof metal.


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## teejk (Jan 19, 2011)

kinda too late SASmith…that material goes on before the roof steel and I think he'd be crazy to remove it (those washer head screws are meant to go down once and only once).

if we get a better idea of the framing, he'll have a pile of BTDT suggestions (and several in this group tend to buy Harbor Freight stuff so we know he'll get a mix of solutions from Rolls Royce to Yugo). Let's watch and learn!


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## a1Jim (Aug 9, 2008)

Sorry for your problems Alistair
Spray foam seems like your best choice ,I've found that sometimes paying someone to do the job cost the same is buying the material and equipment to do it yourself. Paying someone gets you a guarantee .ether way it's not cheep.
I would be calling the guys who put it up an ask them why they didn't tell you about this problem.


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## teejk (Jan 19, 2011)

a1Jim…he/us will get it figured out! trust us!


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## a1Jim (Aug 9, 2008)

Teejk 
Since I'm a contractor of 25 years I thought I would offer Alistair my input.


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## teejk (Jan 19, 2011)

a1Jim…I didn't mean to offend but have you done steel buildings without a ceiling before? we are talking about "pole barns" (I think…hard to tell).

I contracted for 30×56 on slab (radiant in-floor heat) finished with white steel interior walls and ceilings (10'). Prior to selecting my design, I did do some reading and learned that spray-on foam and steel do not get along at all. That was a 4 years ago and perhaps the technology has improved but I doubt it…the steel might be 23 ga at best and even in my shop it snaps/crackles/pops with temperature changes. The issue with spray-on is the steel moves a lot and the foam develops fissures…moisture gets trapped and the steel rusts from the inside out.

let's get a better idea of what we are talking about and help the guy out with the best/most economical solution.


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## a1Jim (Aug 9, 2008)

I don't think that anyone on Ljs has the right to tell another member to shut up or stifle them self whether the other person knows what there talking about or not. Alisair has been a friend of mine for some time.

I've only built a couple dozen pole barns in the last ten years . The problem is the contrast between the hot and cold so you don't need 12" of foam. The last pole barn roof that I built and had a spray job the customer contracted himself and has been in place about 5years ,as has been stated earlier it would have been better to insulate before putting roof on with the standard roll out insulation. The spray on material may differ but they one I was just talking about has lasted this long and I doubt he will have problems in the future.


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## juniorjock (Feb 3, 2008)

wow


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## noblevfd (Dec 7, 2008)

I built a 30 by 50 pole barn bought as a kit and it came with bubble wrap foil on one side white on other side to prevent condensation or I could have went with osb with same results you don't need allot the wrap comes in 48" rolls and will not absorb moisture like fiberglass I used prodex insul on the side walls would also work both are only around 1/4 in but if you are all steel don't how you would fasten to roof sorry to hear about your problem hope you can come up with a fix

good luck
noblevfd


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## Grandpa (Jan 28, 2011)

I had a problem like you are talking about. It rained inside my shop a couple of times. Really messes up your tools. I had an uninsulated building with a metal roof and no ceiling. When I moved to the country I built another building and this time I added fiberglass insulation. This was about 2" thick and there is a vapor barrier on the inside. The metal covered the insulation. I have this on the walls and ceiling. I heat with a kerosene heater and have not had a problem in the 12 years I have lived here. Maybe you could add something. I see a lot of blown insulation that adheres to the inside of the metal. It seems to work.


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## gfadvm (Jan 13, 2011)

Alaistair, Stay away from the blown on paper mache looking insulation. It looks good when first done but will soon begin to separate and drop huge clumps! I think the spray foam doesn't have this problem but you may have to prep the metal before spraying as most sheet metal has a thin oily coating that bakes off the outside quickly in the sun. Not so on the inside. I had problems painting the underside of a metal roof until I prepped the surface.


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## a1Jim (Aug 9, 2008)

Sounds like Grandpa has a good idea just wondering how you hung the insulation on the ceiling if you had metal trusses?


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## Grandpa (Jan 28, 2011)

My insulation was put over the purlins then the metal was added. This traps the insulation and also squeezes the insulation to ….well, really thin in those areas. I know this isn't the best situation but it is done a lot in our area. Using chicken wire first then putting the insulation on then the metal is a good system. My interior is white since the moisture barrier is white. The insulation is part of the enevelope. That is a good question. Guess I left you hanging. We do that a lot in SW Oklahoma. The temps are moderate and this works for us. BTW my daughter posted a photo on Facebook yesterday (Dec 6) of my grandaughters in their front yard. They had been swimming at the rec center and were wearing their swim suits and had a terry cover up thrown over their shoulders. Moderate so far but we are expecting some cooler weather next week.


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## RonInOhio (Jul 23, 2010)

Kerosene and Propane heaters create a lot of moisture. Obviously losing a lot of heat out the roof.

Best bet is to put up rigid insulation board or Reflectix from the inside if practical. Any kind of R factor would probably take care of the condensation. Might want to consider some kind of gable vent first and see if that helps.


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## renners (Apr 9, 2010)

Best wait for he photo guys. What you on the left side of the Atlantic call a steel shed is a different thing to what those on the right side call a steel shed.

Steel Shed (American) - Massive steel structure, fully tricked up, Interlocking insulated panels, a woodworkers dream.

Steel Shed (UK) - Probably 6×8 or 8×12, small box steel welded frame, uninsulated corrugated tin sheeting, siting on breeze blocks, a garden shed.

That's not to belittle Alistair's shed, but I think you're overdoing the solutions because your definition of steel shed is a whole lot different than what the shed probably is.


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## Howie (May 25, 2010)

I think the combination of spray on insulation(Jim) and added circulation (Mike and others) will fix your situation.


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## macatlin1 (May 5, 2010)

My metal shed had the same problem and I found that the moisture was coming up from the concrete floor. I got some old vinyl flooring and covered the concrete and used carpet tape (double sided) to hold 6 mil plastic to the tube frame work that makes up the shed structure. The plastic only goes to the roof corners so any drips that do occur can escape. The only trouble I have had is the tape can't stand the summer heat and the plastic starts to come down in places.


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## SCOTSMAN (Aug 1, 2008)

Jim is a dear friend of mine and I welcome any input he has to offer without being insulted an insult to him is an insult to me.Thanks all others


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## dhazelton (Feb 11, 2012)

No much info to go on here - is it heated and what type of heating (gas furnace probably the worst offender)? Is there a poured floor with a vapor barrier?

The two pound (high density, closed cell) foam does not cause rotting, as 1 inch of that spray has a full permeability rating, meaning moisture will NOT migrate through it. The open celled foam is not as effecient and moisture will easily travel through it. Foam is incredibly expensive, but basically the best stuff there is.

The rolls of insulated foil will help, but retrofitting is not as efficient as installing during time of construction. You can do it, just a pain in the butt and you'll want to tape the seams which is difficult when the material is up there unsupported.


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## teejk (Jan 19, 2011)

sorry Scotsman…I wasn't insulting him. I was basically saying that more information was needed and that the collective wisdom of this board (Jim included) would certainly come up with an effective solution.


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