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Scooter · 10-19-2007, 04:21 PM

I have no idea where to post this......

Our 20x40x15'high metal RV shed gets condensation and drips when it rains. But not every time it rains. And not at other times. Not during summer and fall.

I can't figure it out. I was not paying close attention last year when this occured. So far this year it has rained a few times, light and heavy (we are at 5 inches since 1 Oct) and NO condensation.

We are in Oregon and relative humidity inside the shed is at 90 percent as per my trusty Radio Shack indicator. No condensation and outside temp is 55 degrees. Inside shed it is also 55 degrees.

The shed is not air tight. It does not leak water but there are gaps at the corners and elsewhere because the panels are corrugated. So there is air movement.

Insulation contractor told me that when the difference between inside and outside air is 2 to 3 degrees, that is when condensation forms. I dunno.....

Anyone out there have a metal shed with or without condensation. With or without insulation?

Thanks

Scooter · 10-19-2007, 04:21 PM

I have no idea where to post this......

Our 20x40x15'high metal RV shed gets condensation and drips when it rains. But not every time it rains. And not at other times. Not during summer and fall.

I can't figure it out. I was not paying close attention last year when this occured. So far this year it has rained a few times, light and heavy (we are at 5 inches since 1 Oct) and NO condensation.

We are in Oregon and relative humidity inside the shed is at 90 percent as per my trusty Radio Shack indicator. No condensation and outside temp is 55 degrees. Inside shed it is also 55 degrees.

The shed is not air tight. It does not leak water but there are gaps at the corners and elsewhere because the panels are corrugated. So there is air movement.

Insulation contractor told me that when the difference between inside and outside air is 2 to 3 degrees, that is when condensation forms. I dunno.....

Anyone out there have a metal shed with or without condensation. With or without insulation?

Thanks

RV Wizard · 10-19-2007, 05:29 PM

I think the insulation contractor may be right. Maybe more air flow would be better than not enough.

CD · 10-19-2007, 07:03 PM

Scooter
We have a metal barn (60X60) that is insulated on under side of the roof. No rain.

NeilV · 10-20-2007, 12:40 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Scooter:
I have no idea where to post this......

Our 20x40x15'high metal RV shed gets condensation and drips when it rains. But not every time it rains. And not at other times. Not during summer and fall.

I can't figure it out. I was not paying close attention last year when this occured. So far this year it has rained a few times, light and heavy (we are at 5 inches since 1 Oct) and NO condensation.

We are in Oregon and relative humidity inside the shed is at 90 percent as per my trusty Radio Shack indicator. No condensation and outside temp is 55 degrees. Inside shed it is also 55 degrees.

The shed is not air tight. It does not leak water but there are gaps at the corners and elsewhere because the panels are corrugated. So there is air movement.

Insulation contractor told me that when the difference between inside and outside air is 2 to 3 degrees, that is when condensation forms. I dunno.....

Anyone out there have a metal shed with or without condensation. With or without insulation?

Thanks </div></BLOCKQUOTE>

My understanding on sheds is that if it is not a heated/air conditioned space then it needs to be a ventilated space not just a leaky space. If there isn't flowthrough airflow then there will be times when condensation is a problem.

Your problem could be a combination or poor ventilation and a bad vapor barrier under your slab. In the cooler months when the water table rises yor slab could be wicking up a ton of water vapor. I would put a good sealant coating on the slab and check out what would be appropriate ventilation options for use in Oregon.

Scooter · 10-20-2007, 04:28 AM

CD: What type insulation, spray-on or sandwiched aluminum foil with the dimples or...........?

NeilV: We are on gravel. No vapor barrier. As a matter of fact outside water will wick up around the edges and in about a foot or so.

NeilV · 10-20-2007, 07:39 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Scooter:
CD: What type insulation, spray-on or sandwiched aluminum foil with the dimples or...........?

NeilV: We are on gravel. No vapor barrier. As a matter of fact outside water will wick up around the edges and in about a foot or so. </div></BLOCKQUOTE>

Scooter,

Well there you go! I would not expect anything less then a condensate problem. You could try putting a preforated drain line under the gravel all around the edges and pipe it off to a leech field or retention area away from the structure.

Let us know which way you decide to go an how it works out.

Pusherman · 10-20-2007, 01:06 PM

Metal roof barns have a history of 'raining' inside due to condensation. A couple considerations..

CD is correct -- insulate the celiling joists (not the rafters) and make sure the attic area is ventilated. You need to add a vapor barrier on the 'warm' side, which is the down side. This should stop most of the rain.

To cut down on the vapor intrusion I would higly recommend putting a vapor barrier down on the floor. This could, of course, mean a concrete floor with plastic underneath, but you might try digging it out, putting plastic down, and then backfilling with a shallow surface of sand (to protect the plastic) and then gravel on top of the plastic vapor barrier.

If you can afford the concrete, I'd go that route. I'd also be sure to take care of the drainage problem around the outside walls as well.

Toby · 10-20-2007, 02:30 PM

Scooter

You did not say you had electricity to the shed. If you do, get a coule of wallmart box fans and put in the windows. You will need to get the moisture out of the inside air. Find "Gordons" fix for treating you slab. He also live in Ore. s/Toby

fun time · 10-20-2007, 03:07 PM

I had the same problem but with a stick building. Made the mistake of having gravel instead of cement orginally and not enough ventilation. Solved it by the following"
1. Had a commercial blacktopper put in commercial grade blacktop then sealed it. That stopped a lot of the moisture right there.
2. Installed gable fans on timers which run about 6 hours a day in the fall and spring and about 2 hours a day in the winter depending on the weather. That took care of all moisture. You would not believe what those gable vents with fans do for keeping things fresh and moving air. Highly recommend it. I just installed a similar vent but lower to keep air moving under the MH. Good luck

CD · 10-20-2007, 07:59 PM

Scooter
I don't know what brand etc. of the insulation is. It is against the metal. The barn is not tight by any means as it has door openings for the animals that are always open. It also has an open vent at the peak of the roof.

doc · 10-21-2007, 04:58 AM

A friend of ours has an insulation company and has just bought a second spray machine. This thing sprays two chemicals that mix in the head as it is sprayed on the wall. It expands into a foam and hardens in minutes. He then comes back with some sort of device that cuts the excess off level with the studs. Sort of like the stuff you buy in a can at Lowes or Home Depot except he does 4 and 5 thousand square feet homes.
Not only would this stuff stop the moisture weepage, it would tighten up the metal fabrication and also make it quiter as well.

Downside is that it is not cheap.

NeilV · 10-21-2007, 05:24 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by doc:
A friend of ours has an insulation company and has just bought a second spray machine. This thing sprays two chemicals that mix in the head as it is sprayed on the wall. It expands into a foam and hardens in minutes. He then comes back with some sort of device that cuts the excess off level with the studs. Sort of like the stuff you buy in a can at Lowes or Home Depot except he does 4 and 5 thousand square feet homes.
Not only would this stuff stop the moisture weepage, it would tighten up the metal fabrication and also make it quiter as well.

Downside is that it is not cheap. </div></BLOCKQUOTE>

The moister comming in from the slab or the lack of a slab in the original posters case would still need to be addressed first. Icenine type insulations do seal up a building and dehumidification can then become a critical factor with its use. The mosture would be masked but would not dissapear and sealed in like that could do more damage then before.

calliopeguy · 10-29-2007, 03:45 PM

I had the exact same problem with my metal shed, small vent openings in each end, gravel floor. The condensation was so bad it actually was a layer of water on the bottom of the roof. I have since moved and built another metal metal shed (30' x 60'), concrete floor. This time I also put in three (3) 10' vent caps on the roof peak...absolutely zero condensation. For me I believe the answer was maximum ventilation.
Ken