Proper Roof Ventilation

jonathan03

I have a three story house with a metal roof, 10/12 pitch. There are 2x4 joists and the owner packed them full of insulation and drywalled over them. There is no ventilation so obviously the drywall seams crack all over. What is the right way to vent a roof on a house like this? Do I need a vent on the outside to the exterior or a vent on the inside to the interior? I would like to have a finished third floor but the seams keep cracking.

Thanks.

Mark Harvey

Venting a roof is important because it lets the warm air from the inside escape rather that accumulate at the highest points. There should be vents (Soffits) under the eaves on the outside and and vents high up on the roof. This allows for proper circulation. Chec out a ridge vent on the net to see an option worth considering. The ridge vent may be the easiest solution to your issue. Also, there should be a space between the insulation and the roof sheathing to allow for air movement. If the insulation is over sized, blocking the flow of air, the problem may (probably will) continue.
Good luck.

jonathan03

I should have added that my house is 130 years old, balloon frame construction with a 10/12 pitched metal roof. It has box gutters which I need to redo anyway. The third floor is a half story and I want to keep it finished.

Should I add vents in the bottom of the box gutters like soffits in new construction? Or is it a waste of time because something else will block the flow of air?

Mark Harvey

With a building of that vintage, I'd contact a local roofing company or history buff to see more about the actual construction. The principal is the same in that you should have proper ventilation but I'm not sure what can or can't be done without disrupting the integrety of the building. Again, ask around. If you know of other buildings of a similar nature, especially in your neck of the woods, ... if you feel comfortable... knock on the door and ask the questions. Others may have gone through this before and you won't have to re-invent the wheel. Hope this helps.

AaronB

Your ceilings are probably cracking from the weight of the drywall and/or snow load.

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