Can anybody provide / point me in the direction to how to properly insulate/vent a mansard roof. I am currently getting alot of icicles which indicates that heat is getting through the roof and melting snow, causing huge icicles. <!—-><!—-><!—->
There does not appear to be any proper ventilation in place. <!—-> <!—->
How do I ventilate this roof? I would think that a vent on the flat part of the roof would be asking for leaks. Should there be vents installed near the top part of the sloped section? Should I just blow a ton of insulation into the top part, and behind the sloped sections and hope for the best?<!—-> <!—->
I should add that there is an apartment on this level which is currently vacant, but i would rather not do too much damage. <!—-><!—->
PLEASE HELP! <!—-><!—->
PS: Is Dino still on this board?
Replies
There does not appear to be any proper ventilation in place.
A proper Mansard roof (steep sides up to a flat, parapet-less top) is a classic example of how you can't simply mandate that venting a roof will equal no problems with that roof.
Now, are the icicles on the bottom of the sloped roof, or at the joint between flat and sloped? Any signs of leaks from the flat roof?
Normally, the mansard sloped section is too steep to have much ice dam worry--normally.
Now, are you seeing other things to worry about (like signs of roof leaks)?
PS: Is Dino still on this board?
He's around, he's also a bit busy, too.
Hi there, thanks for the response.
The icicles are at the bottom of the sloped roof, on the overhanging part (near the soffits) I am not seeing any signs of a leak, but its on the roadmap to have the roof replaced, both the flat sections and the sloped parts. When redoing, I will have them I&W the sloped part.
I am in the attic (3rd floor apartment) doing some reno's .. removing baseboards..adding new wiring etc.. and have not seen any evidence of water damage and thats a good sign, but there are several areas where the plaster has separated from the lathe (indicating problems in the past?? maybe?).. on a side note.. where can I buy plaster repair screws and washers online?
so, .. i guess my questions are :
A) should i worry about the immense icicles?
B) should i add a ton more insulation, to keep heat in the apartment from melting snow and turning into icicles
C) should i add more ventilation?
D) should i hire a wrecking crane?
Thanks to all :)
D) should i hire a wrecking crane?
Dunno <g> I'm not the world's biggest Mansard fan--I'm likely not the best person to ask. <g> The question really will be if your local AHJ requires more than you presently expect (a less-than desireable Surprise!).
C) should i add more ventilation?
I'm the last person to ask about that--I'm no fan of ventilation="good" roof (the science does not really back that up except in very narrowly-defined climate regions).
B) should i add a ton more insulation, to keep heat in the apartment from melting snow and turning into icicles
Hard to argue against a person wanting to add more insulation. The trick of it would be in installing the insulation out of contact with your cold surfaces. The big, giant, weak point in a Mansard is that joint from flat to sloped. It has zero tolerance of uh-ohs. It's where you are most likely to see snow melting into an ice dam I'm thinking, and ading a frozen, non-draining parapet to the edge of a person's roof hardly seems like a long-term good thing.
The (very possibly) real issue you might need is in draft-proofing the interior ceiling-to-roof juncture (especially as it's very likely you have the ceiling hung from the flat roof's "rafters" and thus have no way to decouple heat transfer from the ceiling inside through the rafter and then out to the roof deck above.
A) should i worry about the immense icicles?
Maybe, especially if the weather goes through the swings we've had locally, I'd not stand underneath any of them <g> . . .
Hopefully some one with significantly more northern experience will chime in on whether one wants a different/better/unique-to-climate drip edge where icicles collect.
Hmm, bears thinking about, and it's after 1700, and I clearly need some brain lubricant (been a tough day in the trenches of architecture).Occupational hazard of my occupation not being around (sorry Bubba)
Hi Again,
There is acually an 3 ft attic space between the ceiling in the apartment, and the roof where i can access to blow in insulation. I think i can access behind the sloped sections from within this section, but am not positive.
Are there any other 'experts' on this type of roof in a canadian climate?
Thanks!Rav
RE: Plaster WashersTry Vandykes (sp) supply, they have a web site. Also, Charles Street Supply, Charles Street, Boston, carries them also. Oh, yes, HomeDespair also carries them (at least the one in my City does).Renaissance Restorations LLCVictorian Home Restoration Serviceshttp://www.renaissancerestorations.com
My take is that insulating with a foam product ought to do the trick. We used Corbond in the sloped walls and the pitched roof as well. We installed Grace Ice & Water shield on the original roof deck, plus Royal Duraslate to cover the thing up.
The Corbond approach really only works if you have access to open cavities. Otherwise, a poured Icynene or dense-pack cellulose might work better.
We eliminated the roof vents and have lived happily ever after. We have no icicles anywhere, our roof stays covered with snow and ice long after after all other roofs in the area have gone bare. The only area where we have issues is the standing-seam copper roof areas below the main roof where insolation causes some issues by melt/freeze action.