DIY Chatroom Home Improvement Forum

DIY Chatroom Home Improvement Forum (http://www.diychatroom.com/)
-   Building & Construction (http://www.diychatroom.com/f19/)
-   -   Existing Cathedral Ceiling Insulation Question (http://www.diychatroom.com/f19/existing-cathedral-ceiling-insulation-question-88790/)

Bob Deb 12-06-2010 12:35 AM

Existing Cathedral Ceiling Insulation Question
 
I searched for this topic & came close, but did not find one that actually matched & hope someone can help.

I am located in New York State & right in the middle of reinforcing the cathedral ceiling of my house due to a major sag. In the worst area, the sag is about 3 inches in less than 6 feet. Before I replace the asphalt shingled roof this coming spring, I decided to inspect the roof structure more closely.

I believe the sag contributed to the cracking & splitting to many of the original asphalt shingles. The house was built in 1987, & the rafters supporting the roof are 2x8's that span 20 feet between the front wall & the support beam at the other end. They probably should have been at least 2x10's minimum.

The existing R19 fiberglass insulation has a vapor barrier & is almost as thick as the depth of the 2x8 rafters, so there is little or no air space for ventilation. I plan to correct the sag on the exterior by adding 2x furring strips contoured to the sag once I tear off the shingles. A layer of plywood sheathing over the furring strips will give me the air space I need above the insulation.

For the interior, I am going to do something similar by adding 2x rafters below the existing 2x8 rafters & a lightweight T&G cedar planking for a false ceiling below the drywall. When I do this false ceiling, I am considering the installation of addition insulation. I was also hoping to avoid the removal of the existing drywall & R19 insulation because of the large area it involves as well as the height.

My question is, will there be any moisture problems by adding insulation below the existing drywall & R19 insulation, & am I going to gain any R value by doing this?

Here are some pics showing how I started the framing. The new beam spans 17 feet & made from two 2x10’s sandwiching Ĺ inch plywood. It’ll be supported every 6 feet with diagonal bracing that is also two 2x10 lumber, & tied to the wall & the 2nd floor, floor joist framing.

http://img.photobucket.com/albums/v5...mCeiling2A.jpg



http://img.photobucket.com/albums/v5...ndofBeam1A.jpg



http://img.photobucket.com/albums/v5...ndofBeam1A.jpg


http://img.photobucket.com/albums/v5...eofCeiling.jpg



http://img.photobucket.com/albums/v5...wwScaffold.jpg

Ron6519 12-06-2010 08:57 AM

It doesn't look like the beam supports the roof framing along the entire room width.
I would have removed all the roofing before putting up a permanent solution. That way the roof framing would be more easily adjusted to the proper level. Using what you have as a stop gap winter measure makes sense as the roof is severely under structured.
You might have used an engineered beam for the load and not needed all the extra framing.
How did you fasten the beams together?
Ron

Bob Deb 12-06-2010 10:22 AM

Quote:

Originally Posted by Ron6519 (Post 546454)
It doesn't look like the beam supports the roof framing along the entire room width.
I would have removed all the roofing before putting up a permanent solution. That way the roof framing would be more easily adjusted to the proper level. Using what you have as a stop gap winter measure makes sense as the roof is severely under structured.
You might have used an engineered beam for the load and not needed all the extra framing.
How did you fasten the beams together?
Ron


You're correct, the new beam isn't supporting any of the rafters yet. I'm not done, & will be adding material between the top of the beam & the bottom of each rafter once I have all the new framing completed & the beam properly supported. I'll tie it all in with rafter ties (hurricane straps) as well. Each one is a different distance from the new beam so it will be a pain in the neck.

The beam span is approximately 18 feet & is constructed of two 2x10's with plywood sandwiched in between. I used construction adhesive & screws, & it will be supported by the diagonal bracing you see in the photos at 4 locations about 6 feet apart from one another & also made from 2x10's. The diagonal bracing is anchored to the front wall of the house & the edge of the floor joists of the 2nd floor loft.

I'm using 2x6's to create the supports & bolting them all to the diagonal bracing creating a truss. I'll have photos later to help clarify what I did. I would have liked to have used an engineered beam like I did to support the loft I built 12 years ago, but to install that would require opening a wall to get the entire length of the beam into the pocket where it sits. The beam I just installed was built in place.

I agree, tearing off the roof would help with getting the rafters back in position, but I am working alone during my vacation time & on a limited budget. I can't risk exposing the interior to the possibility of some really bad weather. The way I am looking at the overall project now, is that the sag will never get worse & there will not be structural failure with the additional framing I am installing.

I appreciate the input & the good eye. :thumbsup:

Ron6519 12-06-2010 12:01 PM

Screws are a generic description. The fasteners need to be rated to the task.
You can probably jack the beam into a close position using a 20 ton jack. The tricky part will be stabilizing the load at that height while you shim the ends. I've used 4x4's attached to the top beam that were inclined at the floor. As I raised the beam, the posts were tapped slowly to the vertical.
Ron

Gary in WA 12-06-2010 12:56 PM

The main problem I see is supporting your new framing (6'on c. 2x10, and 2x6 verticals, struts) all within 2' of the cantilevered floor joist. Why not just add 2x6 struts from beam to plate at the cant.? With drywall behind the lower ledger, the shear is mostly gone, though 3/4 the load would be on the cant. anyway. 17' span w. 2-2x10 Doug/fir at 1500fb will carry 2100# total load. If carrying 10' of rafters times 17' span = 170. 2100#/170 = 12# load. But, if only carrying the sagging rafters, 6' x 10' span = 60. 2100/ 60 = 35#, or 25# live load and 10# dead load, material. That's without struts to the already maxed out cantilever. Hope there is a healthy header over the window under the new beam and some floor blocking under the post at other end. Have a S.E. check it out and take the liability from you.

Gary

Bob Deb 12-06-2010 01:12 PM

Quote:

Originally Posted by Ron6519 (Post 546581)
Screws are a generic description. The fasteners need to be rated to the task.
You can probably jack the beam into a close position using a 20 ton jack. The tricky part will be stabilizing the load at that height while you shim the ends. I've used 4x4's attached to the top beam that were inclined at the floor. As I raised the beam, the posts were tapped slowly to the vertical.
Ron


I appreciate the input but don't worry, the Simpson fasteners are adequate for what I am doing. The beam that's been constructed is already in place, so I am not going to alter the plan. I did use a jack to install the engineered beam when I did that, & supported it with a temporary scaffold set up. Please remember that this new beam is not the primary support for the entire roof system, it's only there as a secondary measure to help distribute the weight. The building was constructed by the previous owner in 1987 so it isn't new & it's been up for some time.

The question I still need to get an answer to is about insulation & vapor barriers & how I'd like to add to what is there for a better R value.

By the way, here's a pic of the truss style support I mentioned earlier.

http://img.photobucket.com/albums/v5...rBracing1A.jpg

http://img.photobucket.com/albums/v5...rBracing2A.jpg

Bob Deb 12-07-2010 09:01 AM

Just bumping this for my insulation question.

"My question is, will there be any moisture problems by adding insulation below the existing drywall & R19 insulation, & am I going to gain any R value by doing this?"

SteelToes 12-07-2010 10:02 AM

Quote:

Originally Posted by Bob Deb (Post 547271)
Just bumping this for my insulation question.

"My question is, will there be any moisture problems by adding insulation below the existing drywall & R19 insulation, & am I going to gain any R value by doing this?"

Yes, adding more insulation will result in greater R value.
In my opinion itís not a good idea to trap gypsum between two insulators.
Remove existing drywall and insulation add 2x6's to the rafters and install new PF insulation min R30.
This will allow for a proper air gap and better ventilation.
On the outside new 5/8 cdx sheathing and new ridge and soffit vents

Bob Deb 12-07-2010 07:54 PM

Quote:

Originally Posted by SteelToes (Post 547311)
Yes, adding more insulation will result in greater R value.
In my opinion itís not a good idea to trap gypsum between two insulators.
Remove existing drywall and insulation add 2x6's to the rafters and install new PF insulation min R30.
This will allow for a proper air gap and better ventilation.
On the outside new 5/8 cdx sheathing and new ridge and soffit vents


I had a hunch it would be a problem, I just wanted another opinion. I may end up removing the sheet rock at a later date in smaller sections to avoid a 3 story, demoliton with scaffolding.

Thanks. :thumbsup:


All times are GMT -5. The time now is 11:56 AM.


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