Pole Barn Condensation

[Dayong]

This message is a reply to an archived post by UP Oliver on June 30, 2013 at 18:17:00.
The original subject was "Pole Barn Condensation".

I just came back from my pole barn at 11am. I have a lot of moisture (frost on inside the roof)in my barn and its dripping. I have a ridge vent the eves are open, I have a 16 foot door open, and a 8 foot door open, and it did not snow or rain for days. can't be inadequate ventalation. It must be the temperature and moisture from the ground because I don't have concrete floors

 

[Mike M]

Sounds like the builder did not put a vapor barrier under the roof sheeting. That's a big NO NO.

 

[Dean]

You need the plastic bubble lininig beneath the metal.

I've never had a drip of any type from mine regardless of weather.

Dean

 

[rustyfarmall]

I've got the vapor barrier under the concrete, vented roof ridge, and vented eaves. Most of the time it all works quite well, but occasionally, under certain weather conditions and temperatures, the floor will be damp, and the tractors parked inside will be "sweaty". Only way to stop it, I think, would be a fully insulated and climate controlled interior.

 

[paul]

I had that the first year.

Since then its a very minor problem, can't see I never see any condensation, but not enough to drip.

The first year, the wood, the dirt, the gravel, it is all evaporating out moisture.....

I was worried that first year. I didn't think it would be a problem, as dads old shed from 1962 never ever sweated. Tho it was a poured concrete stem wall, not a pole barn, so the ground dries out and stays dry. A pole barn, the moisture can seep in from the side and keep the floor damp on you?

Paul

 

[Geo-TH,In]

A pole barn like yours is a good lesson in relative humidity, dew point and condensation.

As a kid growing up on a dairy farm, our cattle shed which was open on the south so cows could come and go as they wanted. It was an ice cave at night. As soon as the sun came out the frozen condensation melted and it was a stinky rain forest. 50 years ago I don't think anyone cared about moisture barriers.

I designed my pole barn without a metal roof. I've never had the first condensation issue. I used 1/2 inch OSB and 35 year shingles. I have a 6 inch concrete floor. NO PLASTIC under floor. I can park a truck in barn covered with snow. Floor can be wet. ABSOLUTELY NO CONDENSATION PROBLEM.

That's why I'm not a fan of metal roofs. I learned that lesson 50 years ago.

 

[NoNewParts]

gutters?
Take a walk away from the shed so you can see the big picture of the ground grade.
I had that problem with one of my dirt floor sheds.
Water migrating underground keeping the floor damp.
Never any water visible above ground.
I added a lot of drain tile, a few under the dirt floor and more tight along the outsides of the building.
dry now

 

[MtMan]

I used one inch insulation under the metal roofing and mine is enclosed and no moisture at all.

 

[Nancy Howell]

We had a problem with condensation on the underside of the roof from the warmth of the hay. The water would run down to a purlin, collect, then drip on the hay causing black mold.

It was way past the point of being able to put insulation up.

Since the purlins were wood, I bought about 20 yds of terry cloth, cut it in long strips and tacked it to the purlins.

The terry cloth (bath towel fabric) absorbed the water and solved the dripping problem.

 

[Cas]

One of my pole barns has a dirt floor and no moisture problem. Hauled in 1&1/2 to 2 feet of gravel to get it off wet ground.
Our winds come come from the southwest and the building is east to west.
I would take some dirt out and haul in a little gravel. As mentioned previously, grade around the building should carry water away from building. As a side note we are on heavy clay.

 

[Texasmark1]

Having had "sheds" with corrugated metal roofs sweat down to the purlins and drip from there, when I had my shop built I had the roof ridge vented and bubble/alum/vinyl roll insulation applied before the metal roofing.

Nar a sweat problem regardless of the weather and yes if you open the doors and let cold damp air in, the floor will sweat even with 3 mil plastic under the slab and anything that was colder that the prevailing moist air will condensate.

So my shop has a 15' roof extension which I use for a parking area for whatever. It is just the sheet metal with no insulation and surenuf water droplets on everything from the purlins.

Mark

 

[RayP(MI)]

Just completed a new pole barn. On the recommendation of my builder, we went with 2 foot spacing on the rafters, 1/2 inch OSB, plastic underlayment and then the steel roofing. We'll see if there is a problem with condensation.

 

[bill mart]

George, do you have to worry about snow load ? Bill

 

[Russ from MN]

We stretched a heavy felt type material (scrap from a paper machine) over the roof purloins before putting the roof steel on. Then we put plastic down on the floor and another heavy paper mill fabric over that. No condensation dripping and I can sweep the floor clean.

 

[Mark6005]

Roof ridges on one building and roof cupola vented on another seem to keep them dry except during damp warm fall weather. Then I get drips. But not too much to worry about.

 

[David G]

Moisture comes up from the floor.

 

[Dave H (MI)]

We have a builder in the area who specializes in pole barns. Has built barns for most of the larger farms in the area. He recommended OSB, then a fabric approved by the steel supplier, then a steel roof. He was absolutely firm that there be no traditional plywood, says he had too many callbacks on it. Does not like shingles either. We hired him for our barn. Meeting to get the site work scheduled Saturday.

 

[bill mart]

why do some builders put OSB under the steel? bill

 

[Texasmark1]

I guess OSB is plastic film. Purpose it to prevent ground moisture from coming up through the concrete.

If the slab is cooler than moisture laden ambient air it will sweat regardless. Just like a glass of iced tea on a hot, humid summer day. The glass is cooler than the ambient and the moisture in the ambient condenses on it.

Mark

 

[Russ from MN]

Oriented strand board (OSB), also known as sterling board, sterling OSB, aspenite, and smartply in British English, is an engineered wood particle board formed by adding adhesives and then compressing layers of wood strands (flakes) in specific orientations

It's a replacement for plywood, more consistent strength and cheaper. Gives you a nice surface to walk on. We put it under steel on our cabin, with tarpaper in between. Time will tell!

 

[Texasmark1]

Okayeeee. Am I to assume that this is done in lieu of a concrete floor?

 

[Geo-TH,In]

My barn was designed my people in Michigan, where snow loading is an issue. My trusses are on 2 ft centers. In 78 we had a bad snow that colapsed some barn and house roofs.

 

[Geo-TH,In]

Where I live the moisture comes mostly from animals and the air, relative humidity. When anything is below dew point temp, mother nature puts condensation on the, grass, concrete, tools, and yes barn roofs.

 

[bill mart]

reason I asked was, lost my barn in 2002 due to snow load. new barn has steel roof and when the snow now gets deep on the roof we heat it up inside with heaters and the snow will slide right off. Bill