Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Building & Construction

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 01-13-2009, 07:34 PM   #1
Newbie
 
Join Date: Jan 2009
Posts: 3
Rewards Points: 10
Default

Will my roof rot?


I have a 1880's queen ann victorian with a mansard roof. The roof comes down alongside the 3rd floor walls and there is no insulation in the wall. The cavity between wall and roof varies from maybe 14" at the top to 30" at the bottom. One insulation contractor told me that he can fill the cavity with insulation (no venting needed) and another company said that I will rot out the roof if I fill it with insulation. Does anyone have any advice or a better way to do it? The most of the walls are plastered.

richk is offline   Reply With Quote
Old 01-14-2009, 06:54 AM   #2
Member
 
Join Date: Dec 2008
Location: Wilmington, DE
Posts: 3,118
Rewards Points: 2,000
Default

Will my roof rot?


In general, insulation that touches the roof sheathing can cause condensation on the underside of the sheathing, which will rot out the deck. Not sure about mansard type roof.

Just Bill is offline   Reply With Quote
Old 01-14-2009, 07:46 AM   #3
Mold!! Let's kill it!
 
Join Date: Feb 2008
Location: Central Pennsylvania
Posts: 2,849
Rewards Points: 2,012
Default

Will my roof rot?


You need to maintain at least 1-1/2 inches of free space between the insulation and the roof deck for air flow.
Maintenance 6 is offline   Reply With Quote
Old 01-14-2009, 07:48 AM   #4
Remodeling Contractor
 
Join Date: Dec 2008
Location: Sandy Hook, CT
Posts: 3,590
Rewards Points: 2,000
Default

Will my roof rot?


Both are right. You need to keep the ventilation throughout the roof and you can insulate. But not with the blown insulation suggested. Check with a contractor providing icynene system. This is a spray foam that allows air to still circulate, and insulates better than any other system. Be ready for sticker shock.
Bob Mariani is offline   Reply With Quote
Old 01-15-2009, 11:57 AM   #5
Member
 
Join Date: Jul 2007
Posts: 1,702
Rewards Points: 1,224
Default

Will my roof rot?


So you are talking about the nearly vertical portion of a Mansard roof. I can see why you are getting conflicting advice. Contractor 1 looks at it as essentially a vertical wall and suggests blown in insulation. Contractor 2 looks at it as a roof and therefore needs ventilation.

Can you find out what has been done for other Mansard roofs in your area and whether or not it has caused problems? Local climate is going to be a factor in whether one technique or another is the best choice. It wouldn't hurt to get the opinion of a few other contractors that have experience with Mansard roofs.
jogr is online now   Reply With Quote
Old 01-15-2009, 06:04 PM   #6
Remodeling Contractor
 
Join Date: Dec 2008
Location: Sandy Hook, CT
Posts: 3,590
Rewards Points: 2,000
Default

Will my roof rot?


Quote:
Originally Posted by jogr View Post
So you are talking about the nearly vertical portion of a Mansard roof. I can see why you are getting conflicting advice. Contractor 1 looks at it as essentially a vertical wall and suggests blown in insulation. Contractor 2 looks at it as a roof and therefore needs ventilation.

Can you find out what has been done for other Mansard roofs in your area and whether or not it has caused problems? Local climate is going to be a factor in whether one technique or another is the best choice. It wouldn't hurt to get the opinion of a few other contractors that have experience with Mansard roofs.
I had to completely rebuild one in Delaware last summer.. completely rotted out, not ventilation.
Bob Mariani is offline   Reply With Quote
Old 01-16-2009, 08:34 PM   #7
Member
 
Join Date: Jan 2009
Location: South of Boston, MA
Posts: 17,248
Rewards Points: 2,000
Default

Will my roof rot?


Example of a Mansard roof
If they are talking about the part of the roof the roof near the top row of windows then that is roofing. There should be venting
Does the underside of the sloped roof have vents?
Scuba_Dave is offline   Reply With Quote
Old 01-16-2009, 09:20 PM   #8
Member
 
Join Date: Jan 2009
Posts: 489
Rewards Points: 250
Default

Will my roof rot?


You should be able to fully insulate the wall cavities in the lower part of the roof. It acting as the walls not as the roof. The worry is that you are going to impede the flow of air that removes moisture as it rises to the roof. First of all, you probably don't have any type of soffit venting or ridge venting to even make this possible. Secondly, this old house is probably leaky enough where a lot of moisture leaves even before it gets to the roof. If it is going to be a problem, or turns into one, you will have to install some soffit vents and ridge venting.

Josh Jaros (Jaros Bros. Construction)
jaros bros. is offline   Reply With Quote
Old 01-17-2009, 06:17 PM   #9
Newbie
 
Join Date: Jan 2009
Posts: 3
Rewards Points: 10
Default

Will my roof rot?


Thanks alot for all of your input, I'm thinking of taking foam board and attaching strips to the back and then attaching that to the roof. that would allow air to flow through just to make sure it's not a problem. Some of you mentioned ridgevent and soffit vents. I have neither, but the former owner installed a roof fan. Do I need more than that? What about soffit vents? I'll put a pic from the street on my photos.
richk is offline   Reply With Quote
Old 01-17-2009, 06:24 PM   #10
Member
 
Join Date: Jan 2009
Posts: 489
Rewards Points: 250
Default

Will my roof rot?


Soffit and ridge vents complement themselves. You can't have one without the other and expect the system to work. Think of it like a chimney and the smoke like moisture that builds up in your house. As the hot air rises it carries moisture with it. Without an opening to escape at the top, you just have a lot of moisture building up. Without an opening to allow makeup air, you again just have a lot of stagnant air. You need to create a chimney effect for moisture to escape.

Josh Jaros (Jaros Bros. Construction)
jaros bros. is offline   Reply With Quote
Old 01-17-2009, 06:29 PM   #11
Newbie
 
Join Date: Jan 2009
Posts: 3
Rewards Points: 10
Default

Will my roof rot?


thanks jaros bros. Do you think that a fan is enough or will I need add ridge vent. Actually, the mansard roof rises about 3ft above the attic floor and there is another soffit up there. Would it work to put vents in the lower soffits and also the upper soffits? If you look at the pics in my "photos" box you might be able to get a better idea of what I'm talking about.
richk is offline   Reply With Quote
Old 01-17-2009, 06:41 PM   #12
Member
 
Join Date: Jan 2009
Posts: 489
Rewards Points: 250
Default

Will my roof rot?


Most older houses leak enough that you probably don't need excessive amounts of air flow to keep the moisture from building up in your attic. Has the building been tightened up? Where do you live? The coasts tend to have a higher humidity than the central states. Have you noticed humidity problems in the past? Can you take some readings of moisture and temperature to determine if you have enough venting? Do you have air exchangers in this building to get the moisture out? Are there fans in the bathrooms? Vapor barriers behind drywall or on the exterior?

Josh Jaros (Jaros Bros. Construction)
jaros bros. is offline   Reply With Quote
Old 01-17-2009, 06:43 PM   #13
Member
 
Join Date: Jan 2009
Posts: 489
Rewards Points: 250
Default

Will my roof rot?


How much CFM does the fan move?

Josh Jaros (Jaros Bros. Construction)

jaros bros. is offline   Reply With Quote
Reply

Tags
insulation, moisture, roof


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Flat roof questions, advice, ballpark estimate JerryH Roofing/Siding 18 11-07-2008 05:08 PM
Rubber Roof and Roof Deck vianak Roofing/Siding 2 10-09-2008 06:37 PM
Flat roof - Rolled? - leaks Advice? JJ2001 Roofing/Siding 4 11-19-2006 07:17 AM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.