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Condensation Problems
Roof has been in place two years. When frost forms on roof and melts, I get leaks at all (seven) skylights. Roffer did my barn but I find out has never done roof on new construction. Roof is 12/12 pitch, 2x12 with 1/2" OSB, 2x4 horizontal grid over OSB, metal over that. Metal is screwed to 2x4's with what look like sheet metal screws (exposed) with rubber washers. Insulation between rafters inside. Underside of 2x12 rafters are open to living area, I cannot drywall of finish because or exteme moisture from condensation.
HELP!!!! Pllease!!!! Carl D.

I am not sure I am following your question. You talk about condesation but also about leaking skylights. I am so confused! :-)

Anyway, is there any ventilatin in the attic beneath all of this?

Have you contacted the roofing manufacturer for their input?

Can you provide me any more details or even photos?

Todd Miller
Leaks occure at the skylights because the water tracks down the plywood until it hits the header for the skylight.

Styrofoam shields create an air spaces between the insulation and the plywood. They are in each space between the rafters running from soffit to peak. The soffit and peak are vented.

I will call the roofer to get the manufacturer, he bought materials at Menards.

My StarBand internet connection has taken a hit and I will post pictures after it is restored, I am using a temp dial-up and only getting 16K throughput, how do I post pictures?

Thank You for trying to help!!!!!!
Carl, thanks for the additional information. I am guessing the problem is due to improper flashhing around the skylights.

There is no way to post pictures here. What you can do is just email them direct to me at tmiller@classicroof.com

All Best!
Also, Carl, I am curious, is there any underlayment on top of the plywood?

There also may be a problem with the way the ridge is finished.

In most cases, manufacturers of roofing similar to what you have will wnat it installed direct on top of the decking (and underlayment) rather than on top of strapping boards.
New construction house with 2 1/2 x 12 pitch shed roof. We are installing metal roof on perlins mounted over 12" laminates. Plan to drywall ceiling and insulate. What would best insulation type and method be? Should we vent under metal roof or spray foam or cellulose and adhere to metal roof filling in entire cavity? We are in Eastern Ohio, lots of every kind of weather. Thank You!
Ihave read your posts about condensation ;however I think you folks have danced around the complaint.
I am currently working on plans for a mountain home and all of your competition that I have talked to advise me not to use metal roofing as the problem perpetuates to dry rot and serious mold conditions ,be specific what is your rebutal to these statements, FRANK
I have worked withg metal roofing on residential applications for 25 years. I know of many metal roof installations over 75 years old. (Wow -- that's even older than me!) I have never ever ever seen a properly constructed roof system incorporating metal on the exterior which resulted in rot or mold.

I do not know where to even start in answering your question. The post above yours is such a good example of the problem. In it, the writer is talking about installing a metal roof and has already planned out the complete roof system with one major flaw -- no consideration appears to have been given to choosing the right product for his installation (note the low pitch roof) nor to then making sure that the installation is within the manufacturer's specifications.

A failproof roof system will consist of the following, from the living space on outward. Many of the things that I am mentioning here are required by building code, by the way, but still often get ignored.

Drywall or other ceiling finish
Vapor (air) barrier
Properly vented attic space
Solid decking
Quality underlayment
Metal roof covering designed for the pitch of the roof.

It's really that simple yet I see and hear of people trying every variation imaginable, most of them wrong and leading to failure.

Can there be variations to what I have described? Yes but it is critical that those variations meet the installation requirements specified by the manufacturer of the roofing, as well as by building codes.

As an industry, we are trying very hard to educate people about the proper way to construct a residential metal roofing system. However, there are still many many instances of people buying products not really intended for residential application and then installing them on residences with incorrect procedures.

Condensation occurs when warm moist air hits a cool surface. The phenomena of condensation has nothing to do with metal. Any cool material, introduced to warm, moist air, will support condensation.

I have seen many many attics of older homes with standard shingle roofs where condensation and icing are occurring regularly and causing damage. In most cases, this occurs when older homes are remodeled with siding, windows, doors -- all things which make the house more airtight but then no ventilation is added to the attic. As the result, warm moist air which used to escape through leaky windows now migrates to the attic and, because it is not vented out, it condenses.

I am sorry if it appears we have been "dancing". That is absolutely not our intent. The problem is that metal roof systems, frequently metal roof systems not really intended for residential use, are being purchased and installed on homes without correct procedures.

If you want a metal roof for your home, the best thing you can do is work with a Metal Roofing Alliance member manufacturer. Give them a call, discuss your installation, make sure that the installation procedures are correct, make sure that you have an experienced installer. The end result will be a successful metal roof installation.

Thanks so much for considering metal. Please don't give up on us because misinformed people have installed metal products incorrectly, resulting in problems.
Craig, I do appreciate your questions. Thank you.

First of all, with a roof that is just 2.5:12 pitch, you must find a roof system intended for that pitch. Next, you must make sure that the roof system you find is approved by its manufacturer for residential application.

Following the above, I have a hunch you will find a product which must be installed over solid decking and underlayment rather than over purlins, especially for a residential job.

In your case, you will likely end up with drywall, vapor (air) barrier, insulation meeting the requirements of your cold climate, vented attic (soffit and ridge vents), solid decking, quality underlayment, metal roof system.

By the way, increasing your roof pitch to 3:12 or 4:12 will open you up to a much wider variety of product choices.
I believe that the skylights are solid, I can piy a hose to them and not create a leak. Sometimes I can see the water track from several feet above the skylight.

The roofer did work on the ridge that stopped some specific leaks.

When the oof is covered with frost and the sun hits it I have leaks in multiple places, that is why I was thinking it was condensation. I believe that it can happen withother types of roofs, but I have a metal roof.

I will try to contact the manufacturer.

I will try to get a 'certified' metal roof installer to look at my roof.

I was hoping to get an answer like......
"You need to insulate and tar paper before applying the metal"

Thank you, Carl D.
Hi Carl,

Sometimes, it is so hard to really explain things in these postings. There is certainly every chance that there is something going on with your general construction which is a contributing factor here. The fact that some leaks were fixed by working on the ridge, though, really makes me wonder if there are not additional ridge problems.

I would encourage you, if you wish, to call me at my office so we can talk this through a bit. You can also email photos to me. My office number is 1-800-543-8938 ext 201 and my email is tmiller@classicroof.com

Following is a good summary of a roof system that will work. Yes, there are other possibilities but this listing of roof assembly components, from the living space to the outside will work:

1. Drywall or other ceiling finish; 2. Vapor (air) barrier; 3. Insulation; 4. Properly vented attic space; 5. Solid decking; 6. Quality underlayment; 7. Metal roof covering designed for the pitch of the roof.

they put my metal roof on then insulation and sheet
rock nothing else my new seiling is coming down of course they said with all the vents this should not happen even in the tool room their is so much moisture on the metal, this room has not been finished what can we do with out having to rip all off.
the roof has a lot of vents
Building codes call for a 1" vented airspace beneath all roof decks. Ignoring this is asking for trouble, regardless of the roofing material. Additionally, I would suggest an air barrier behind the drywall.

There is no "quick cheap" fix to the mistakes made on this roof. I am sorry.
I have a 35 year old log home onto which i had a copper roof installed. For the most part it is less problematic than the shingle roof (which lasted only 12 yrs.) that it replaced. I live in upstate ny and this season is fluctuating so that it seems to be a larger problem than at first. The condensation is occuring more frequently and expansively. the roof consists of 3/4 tongue and groove, 3/4 ply, 1 1/4 cellulose, 20 gauge cooper. Is it my understanding that their should be a 1 in. gap in the midst and if so where? Also if it is badly constructed could it help to insulate the inside ceiling if so with what would you recommend?

I think i got a bit zealous with sending the first message. I want to say that i think this a wonderful site and i hope to resolve my problems with your help. some of the particularities i left out are the fact that most of the leaks or dripping points are from the cathedral ceiling proximate to the wood stove. Around the skylights and in the adjacent room where there is an area that warm air pools. I've stopped some momentum with fans toward the particular area.
There should be a vented gap between the bottom of the plywood and the insulation. This vents out moisture from inside the home and keeps it from condensing on the cool decking. An air barrier behind the T & G would also be helpful.
You probably have no interior air barrier like Todd noted and warm moist air is moving up through the assembly. Additionally you probably do not have enough insulation which further contributes to heat loss and condensation from ambient air. With no vented air space there is no place for the condensation to migrate out except into the assembly which indicates that a proper moisture barrier may not have been installed. Forcing the hot air down will help reduce the stack pressure however sooner or later you will need to address the deficiencies.
Hi There

Just recently found this forum - it's exactly what i was looking for.
I am in the process of winterizing an existing porch on the front of my house which has a metal roof. I have installed windows and enclosed both open walls. I have noticed on the last few mornings after a cold night that significant condensation is forming on the inside of the roof. How can I eliminate this? Do I insulate from the inside? outside?

I have not insulated the walls or put in the floor yet, but have put in foam insulation to close the openings at the ends of the metal roof, which I know believe is the wrong thing to do.

Thank You

P.S. I am just north of Toronto, Ontario, Canada
I would consider a poly iso spray insulation for the bottom side of the roofing.
Hi Todd,I have bought a Metal Shed 13" Ft X 10" Ft in the back of my Garden,and just want to use it for storage but I have noticed on the last few mornings after a cold night that significant condensation is forming on the inside of the roof. How can I eliminate this? Do I insulate from the inside? outside? another Roof and Plywood?its really bad Condensation,even i am thinking to put wooding floor and Underlayment underneapht,Thanks My email: alboeshi@yahoo.co.uk
Insulating from the inside with an insulation that does not allow moisture to penetrate it should alleviate the issue
As an Architect, I worked on two single family home projects years ago here in Minnesota. We used two different contractors and two different roofers, all very highly respected in this area. Both houses had flat roofs as the Architect I was working for at the time, Ralph Rapson, always wanted flat roofs. One roof was filled with 12" of fiber glass insulation in the 2x12 ceiling joist spaces, then stripped in both directions with wood nailers, then covered with a plywood deck and a BUR. The finished ceiling was sheet rock over a standard 6 mil poly vapor barrier. Metal wind-powered vents were installed in the roof deck to allow the entire roof area to be vented to the exterior.

The second house had the same 2x12" ceiling joists stuffed full of fiberglass insulation, with the 3/4" t&g plywood decking installed directly on top of the joists so there was absolutely no air space above the insulation. A BUR was installed as well. The interior of the exterior walls and ceiling was wrapped with two layers of 6 mil poly which was carefully taped everywhere. The second roof system was not vented, intentionally, in any way whatsoever.

The first roofer said that, of course, a roof has to be vented, especially a flat one here in Minnesota. The second roofer said that with his roof system (and the extra 6 mil poly vapor barrier very carefully installed by professionals), the dew point would be in the plys of the exterior grade plywood roof decking (because there was no dead air space above the insulation and open to the outside ambient temperatures) and, because moisture could not penetrate that decking, there was never any condensation.

Does anyone want to guess which roof failed, partially collapsed and had to be completed replaced?

Of course, it was the first roof, the one that had been vented. There was so much condensation held in the insulation, and above the vapor barrier, that it rotted out the joists; first the sheet rock dropped and then the joists gave way. The solution was to remove the entire roof and framing, re-frame, and foam the entire roof cavity full with no venting anywhere.

Since then I have been vary wary of vented roofs here in Minnesota where the outside air can get down to -30 and drive the dew point into the insulation if there is a vented air space open to the exterior. The logic of the second roofer seems to make lots of sense and his roof is fine after 30 years.

I mention these examples as I contemplate installing a steel roof system (my first)on my unheated (except for a few days in the winter when we will use a wood burning firebox) cabin in Northern Minnesota. I have 3/4" 1"x12" roof boards/decking as the exposed ceilings at an 7/12 pitch over 2x4 rafters with a king-post truss design. I am planning on installing 30 lb felt, then 2x4's running with the rake, eave to ridge, spaced every 4' with 4x8 sheets of rigid foam in between. Then I was going to lay down another set of 2x4's running parallel to the eave, spaced 4' oc, with 4x8 sheets of rigid foam in between. Then I was going to nail down the exposed-fastener steel roofing, using my horizontal 2x4's as nailers for the roofing. Does that sound like a good plan? I don't know how often the steel needs to be nailed in each direction and have seen no directions on other web sites yet. Thanks for ideas and sugestions and comments.
Best approach I have seen used when it comes to insulated roof deck retrofits is well illustrated in this roofing pdf.

Take a look as it describes a very similar approach to your situation.

Many thanks for the suggestion. What Dan is doing is just about the same thing I was going to try; good to see someone else doing it before I try it.

I am concerned about condensation on my roof (I was not planning on building a cold roof for my unheated cabin) because if the eave 2x4 nailers are set horizontally, and if water gets under the metal roof but above the deck, that nailer could act as a dam and accumulated moisture could cause it to rot.


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