Sweating Under A Metal Roof

roof masters

I am relatively new to roofing business, but want to get a reputation for good work and good advice. Customer asked me about problems in a metal roof installed by another contractor. It is a metal roof installed over some rubber-product membrane directly on lath (which was in place for prior cedar shake roof). This metal roof is 5 yrs old and it appears that there has been a problem with condensation and sweating on the warm side of the membrane, causing the insulation to saturate, mold to develope, and some structural wood rot to start. He wants to know what needs to be done to correct this problem. These are vaulted cielings, thus no attic. Is a total redo with solid redecking installation the only solution? Does all the insulation and dry wall need to be replaced? Would like to help him out and would like to get the job, but customer needs to know if the prior contractor has some responsibility to fix the problem.

Mitch M

My only experience with metal roofing has been on the commercial side and that was with pre-engineered steel buildings. My first thought is there is probably no air gap as required by code between the insulation and the decking. This area must be vented. That would allow the warm air to have direct contact with the cold metal thus creating the condensation.

Now, several questions come to mind. How old is it? Was there an Architect involved? And ultimately was it permitted? If it is relatively new, then I think the HO needs to talk with the contractor who put it on and make him aware of it. If it is older then he needs to talk to a lawyer first. I am not saying that the contractor is at fault, but he needs to make sure he does it by the book so if the contractor or whoever is at fault, then he has recourse.

I am sure you want to help the customer, but I would hope more importantly you want to protect your reputation. Be careful of what you say around anybody. I would maybe even go as far as suggesting to the HO to hire an independent consultant so that it stays on neutral ground. That way no one can say that you were trying to create work for yourself.

Try to post some pictures so that we can get a better feel for what is going on.

And last but not least, Welcome to the board!

Justusjeff

What kind of heat source is in the house? I was called to a home with a moisture problem in the attic. The plywood appeared as though someone sprayed it with a hose. Water was dropping onto his insulated ceilings and also running through the exterior of the aluminum eaves. For 17 years the owner ran a coal stove with no problem. He replaced the stove with 2 wall mount non vented gas heaters. The problems started showing up when the units were run longer in the colder weather. One of the by-products of burning any gas, kerosene, etc is water which collects on your colder surfaces..... windows, poorly insulated walls and underside of attic roofs. Just a possibility that should be checked.

red_cedar

Almost sounds like it may not necesarily be the metal roof and might be the "rubber membrane". I wonder if its an ice and water shield?
The membrane may not be letting out any moisture that is being created, in which case it doesnt matter if its solid decking or spaced sheating. If was solid sheating you just would not notice the problems as soon, but would still have the same end result. You could try to correct from the inside like putting a vapor barrier ( plastic sheet ) behind drywall. You mentioned rotted wood members, mold. Might be best to just redo the whole thing but still put the vapor barrier on the inside next time. Stop the moisture before it gets to the insulation.
If you redo, you should be able to reuse the metal.

Roofing contractor fault? Hard to say. Was he was under the direction of another? When I am asked to do something i feel will have problems, I get them ( owner, responisble party ) to sign off on it. Pisses people off but it saves mine and everyone asscoiated with the company ass down the road.

( sorry for the incorrect spelling )

joasis

Be very careful when you follow up another contractor's problems, even 5 years later. You don't want to gain "ownership" of the problem, and thus, liability.

The design is at fault primarily, and it will take some planning and thought, plus an experienced eye to maybe see a workable solution. Being "relatively new" to the roofing world, this is probably one you you co-op with a general contractor on, since the scope of your business is not close to what it will take to fix the problem.

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mics_54

I was going to comment but I think I will just pass other than to say it's an old topic and discussed many times. search the threads....or buy a science book.

Lab Rat

Photos would show everyone reading the thread what you are looking
into but there are countless questions that come to mind starting off.
#1 obviously there is a ventilation issue, what kind of vents are there?
#2 where is the moisture coming from, can it be stopped?
#3 what size is the rafters? Was there enough room for air flow?
#4 what size and type fiberglass insulation was used?
#5 The Membrane was there when the Shake Shingles were on there
why is it sweating now?
#6 The Steel roof was on for 5 years and the moisture problem is
now just showing up?
#7 have the Ceilings always been vaulted? or just recently?
It sounds like its going to be a total gut job if there’s mold involved
and then put in the right ventilation, insulation, take off the old lath and
resheet it. BUT!!
I tend to agree with Joasis, being that you are just starting out
in the roofing business and have not asked the right
Questions that should be asked, then you need to let an
expert in construction take a look at it before you get into
something that could potentially end your early start in roofing.

roof masters

Hey, Thanks for all the advice. Good questions to ask the HO. As I understand the situation, the membrane was placed when the metal was installed; the type of heat is electric and has been the same since the house was built. From the inside it looks like there are a few areas where mold is showing through the sheetrock and the small area where the HO removed the sheetrock was full of mold and some wood root, soaking wet. He had torn out/dumped the insulation so I could not tell what was there originally. The HO tells me that he has contacted the original contractor and the job was subcontracted. Will need to get on the roof to check ventilation situation (it is a very steep roof on a bluff and could not really see from ground). This seems like it may be more than I want to handle at this point, but I don't want to leave the owner in the lurch. He has 2 other larger buildings that need new roofs...