Pole Barn Condensation

I'm about to put up a pole barn to shed equipment and to store hay. I will probably put in some concrete in one end as that will be the only flat spot I have around here.

I was going to sheet the thing with OSB to avoid getting the raining inside so many people seem to have, but after doing the math I am looking at over 5 grand more to go that route with the OSB and extra poles and trusses. This will be a 40 by 80 building by the way.

I have read a ton of stuff online, and I see many ideas on preventing the condensation on the inside of the roof. I live in Upper Michigan so we have major snow load considerations.

I'm looking for input on ways to avoid condensation without spending 5 grand extra. I see where Menards sells a condensation blanket. Has anyone used anything like that or have anything to state that would help me out?

I appreciate the help.

Thanks.

Check out polebarnsdirect.com They have this stuff that looks like bubble wrap with a silver side. the silver side goes against the tin, white plastic side down. It has an R value of 1. I had them put it in my 40x104, with trusses on 4 foot centers. The only drippig I had was directly down the center of the building from the ridge cap, which had to be left open, but it was very minimal, and yes, where I come from, everything sweats bad during the late winter.

IMHO there are 3 things that cause moisture problems in pole buildings.

1. Inadequate ventilation.

2. Lack of vapor barrier under floor.

3. Building is placed on a site with inadequate drainage or high water table. You can't build in a swamp and expect a dry building.

We call it bubble wrap here just some bubbles of plastic between tinfoil. I think the real name is microfoil. Would be light and solve you water problems I think.

Scott,

What happens in an unheated pole barn with a tin ceiling in a place with high humidity is the same thing that happens when you pour a nice glass of iced tea in august. The outside of the glass sweats, because condensation forms from the humidity in the air. humidity is a wicked thing.

If a pole barn roof gets a snow load on it, and the air temp goes up in the day sun, with high humidity, and the inside of the building gets heated up quickly, it literally looks like rain. I can understand it would be hard to imagine if you don't have humidity.

Just be careful with what you use. The bird's love some of the material's used for that purpose unless you keep it tightly closed.

Just as simple as stretching good quality house wrap under the roof steel to control the condensation. Do it all the time here in Iowa ,and a good ridge vent doesn't hurt a thing either.

I just finished putting a roof on my new garage. Walters Buildings has a product that is sprayed on the underneath side of the sheet metal to prevent inside rain. www.waltersbuildings.com Good Luck, Ellis

I live in Indiana. My pole barn was designed by people from Michigan for snow load and was constructed by a crew from Michigan. I had it built with trusses on 2 ft, shingled roof, 35 year shingles, 1 ft vented over hang, venta-ridge down the middle, no plastic under a 6 inch concrete floor, no plastic period, no bubble wrap, nothing on the inside of the OSB, and for the past 5 years NO CONDENSATION. I even park my truck, that I drive daily, in the barn wet, covered with snow, and ABSOLUYELY NO CONDENSATION.

Proper ventilation is the key. No heat, No insulation. Even the floor, never condensation.

IMHO, metal roof will sooner or later form condensation. Where I live, I've seem metal roof on pole barns, removed and shingles installed.
George

(quoted from post at 20:28:32 06/30/13) Scott,

What happens in an unheated pole barn with a tin ceiling in a place with high humidity is the same thing that happens when you pour a nice glass of iced tea in august. The outside of the glass sweats, because condensation forms from the humidity in the air. humidity is a wicked thing.

If a pole barn roof gets a snow load on it, and the air temp goes up in the day sun, with high humidity, and the inside of the building gets heated up quickly, it literally looks like rain. I can understand it would be hard to imagine if you don't have humidity.

Click to expand...

I know what humidity is. I'm in Minnesota. :wink:

The only buildings I am aware of that sweat around here are either on heavy, wet soil, or have poor ventilation. Sweating is unheard of where there is lighter soil,and the building pad has drainage away from it.

Typar or metal roof underlay before steel and problems solved. You can almost solve it with ventilation if the building is in an open and sunny area but that won't work in the trees and in shoulder season if you have snow lay on the roof during warm wet raining days.

Its pretty simple really, anytime a surface is colder than the dew point water condenses on it. You can try to ventilate to keep the surfaces close to the air temp so it can't condense, you can insulate surfaces using the roof underlay or osb so the surface can follow the inside temp faster or you can seal it up and not let moisture get in the building + remove any that does.

The underlay is the cheapest option.

Ridge vent takes care of most of it in my building here in central Iowa.

JM that"s what they used on mine,no drips in over 11 years. bill

Make sure you use poles that have the correct amount of chemical, otherwise they will not last. Must use the proper amount for 'Critical Structural";
Treated Wood

ESR-1980, October 1, 2012

“NatureWood”
Alkaline Copper Quaternary ACQ
0.60 pcf for Ground Contact / Critical Structures / Foundation Use
for Permanent Wood Foundations / Sawn & Round Building Poles
AWPA U1 Use Category UC4A = “Ground Contact, General Use”
for deck posts, fence posts. 0.40 pcf
AWPA U1 Use Category UC4B = “Ground Contact, Heavy Duty”
for Critical Structural 0.60 pcf

“Micro-Pro / Smart-Sense”
Micronized Copper Quaternary MCQ
0.60 pcf for Ground Contact / Critical Structures / Foundation Use
for Permanent Wood Foundations / Sawn & Round Building Poles AWPA U1 Use Category UC4A = “Ground Contact, General Use”
for deck posts, fence posts. 0.34 pcf
AWPA U1 Use Category UC4B = “Ground Contact, Heavy Duty”
for Critical Structural 0.60 pcf




ESR-2240, January 1, 2012

“Micro-Pro / Life-Wood”
Micronized Copper (tebuconazole) Azole MCA
0.23 pcf for Ground Contact / Critical Structural / Foundation Use
for Permanent Wood Foundations / Sawn & Round Building Poles
AWPA U1 Use Category UC4A = “Ground Contact, General Use”
for deck posts, fence posts. 0.15 pcf
AWPA U1 Use Category UC4B = “Ground Contact, Heavy Duty”
for Critical Structural 0.23 pcf

I think I would use most anything but OSB. My first choice would be vinyl faced metal building insulation. It would make the building much cooler on hot summer days. If that was too expensive I would use house wrap such as Tyvek.

I had a 60'X 88' X 16' machine shed put up 5 years ago. Metal roof with 2' overhangs along sides and one end and a 4' overhang over the end that's most used. 5" concrete floor w/re-rod. Extra concrete at ends. No moisture barrier needed under floor because ground it sits on is high, well drained and sandy. Yours might be different. I have ABSOLUTELY NO MOISTURE PROBLEMS inside this building for the following reasons:
1. Black metal roof. Absorbs heat from the sun.
2. Continuous vented ridge with bird proofing.
3. Vented soffets along sides with bird proofing.

The combination of the black roof absorbing heat from the sun with the resulting heat buildup exiting through the ridge vent while at the same time drawing fresh air through the vented soffets is more than enough to ventilate the entire building. Proof of this is no rust buildup on anything. One of my discs has been sitting in the same place for two years and the disc blades are as shiney as they were when it came in. Same with my Great Plains drill which was last used for planting soybeans in 2012. The black roof is also a big help in getting the snow to slide off. Once a little of the roof is exposed to the sun it is amazing how fast it clears the entire roof. Neighbor has the "economy" version of this shed with no vents and he has such a moisture problem that he leaves the doors open for ventilation. Stores most of his machinery outside because it rusts less outside than inside that machine shed. I'm a little south of you in the Green Bay area. As far as snow loading the roof as installed has a 50 year snow load warranty. Trusses are on 8' centers which was called for in my area. Your area might call for closer truss spacing. As far as building quality, my concrete contractor was rather outspoken as to what building mfg put out "crap" and which were better. Mine is generally regarded as one of the better built sheds. Look around your area and ask questions. Do some homework. Builders websites, etc.
I went with white sides, ends and doors to prevent too much heat build up down low. Opening the doors brings the inside temperature down to outside temp in the shade. The 16' high sides help to keep the high temp up where it belongs. I recommend at least 16' high for hay storage and to allow for combine passage. It also makes it easy for the concrete trucks to drive right in when laying the floor. You might need a moisture barrier under the floor but in my case, as soon as the concrete contractor saw what I had, he said: "You do not need a moisture barrier". He was right.

Venting is an absolute. I have used cupolas but got rain inside. On my latest building I used the 10' ridge cap vents, using 2 on a 50' building.

The other thing is sweating. When the roof and the atmosphere are at the same temp no problem. But when the roof is cooler than the ambient it will sweat and drip amount depends upon humidity for one thing. The water will run down the tin to your roof pearlin and drip from there.

To stop it you need a vapor barrier. I have a tin roof and use the vinyl covered rolls containing an air bubble core with a layer of alum foil on both sides and then vinyl over that. It has adhesive where each layer meets the other so that you can seal it all up and if a sag should occur the water couldn't get out.

I have a roof extension to the building of 15' forming a lean-to shed and it drips due to no insulation being under that.

I never had a composition roof sweat, course I always included 15# felt as the first layer over the wood sheeting as others have mentioned.

Felt under a tin roof wouldn't work as the felt would sag and drip in the sags.

HTH,
Mark

Something else I forgot. On poles, in '81 I had Morton Buildings build a building for me. Their building methodology was to put 3 heavily creosote treated short posts, attached together to form essentially one post in the hole with concrete. Stuck out of the ground about 3'.

To that they would attach the upper 3 layered "poles" which were untreated. They used 3 of different upper lengths allowing them to add the upper portion with staggered attachment points for strength.

Today most of the posts are 50% or better eaten away by termites and rot. Expect any day the building will fall apart. Probably not, but will have some serious shifting issues....doors won't fit.

On my new pole barn I installed the poles in plastic socks. The poles are treated and 5" square. The plastic sock is a heavy duty plastic square tube that keeps the wood from touching the soil, sticking up about a foot above the slab. Shouldn't have a problem with that.

Mark

I used to have quite a bit of condensation in my pole barn. Somedays I'd walk in there, everything metal would be wet. I put a concrete floor in, with a vapor barrier, and don't have condensation any more.

The chicken house we put up last year has some kind of felt stuck to the bottom of the steel, it came that way from the factory, it will not peel off, I tried. The contractor said it might sweat a little but the wet felt creates another layer and mediates temperature to prevent further sweating.

Nate

They now make steel roof sheeting that comes with a vapor barrier. Does require a little more care to install. Had a 90X50 erected last summer and seriously thought about going with the new sheeting but since it takes more care and contractors are always in a hurry, decided against it. If doing it myself wouldn't hesitate. Spent over $7000 to foam insulate the roof instead, which isn't a cheap alternative but does work.