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-   -   Insulating an Overhang (https://www.diychatroom.com/f19/insulating-overhang-81297/)

Hurriken 09-12-2010 10:18 PM

Insulating an Overhang
 
My house has an overhang in the front covers both front bedrooms. The floors in both rooms get very cold in this area.
http://img.photobucket.com/albums/v4...Y/DSC_0758.jpg
After finding no tar paper under the roof shingles and one layer of R19 insulation in the attic I have to think they skimped here as well. I tried to pull the bottom plate (sheet of plywood) off so that I can look. This piece of wood is cut to fit perfectly and the nails are flush. I cannot get it off. I don't want to break the front siding or the brick in the back. The brick flexes when I put pressure on it with a wonder bar.

Take a look.
http://img.photobucket.com/albums/v4...Y/DSC_0759.jpg
http://img.photobucket.com/albums/v4...Y/DSC_0760.jpg

In the top photo you can see I removed the trim against the brick but there is no way to pry it down. I was hoping this would be a single afternoon job but alas that never happens does it?

What can I do here? I'd like to avoid replacing the board entirely but if it has to be it has to be.

A) I thought about cutting a hole big enough to fit the pry bar in and try to pull it down.

B) I guess I could blow insulation in there through holes but I'm thinking that because the area is not that big it wouldn't be cost effective to rent the equipment.

C) Is the some tool I don't know about that could help me get at those nail heads? They are common nails.

Tom Struble 09-12-2010 10:26 PM

its probably just 1/4'' ply you could remove the nails with a catspaw or you could try to drive the nails thru the ply with a large nail set or punch

Scuba_Dave 09-12-2010 10:27 PM

Do you know if there is any insulation in there ?
How far down does that front siding hang down over the plywood?
I'd be inclined to put up 1-2" rigid foam then another piece of plywood
Put a piece of trim on the very front if needed to hide it

I might even box off between the 2 beams & add R30




Hurriken 09-12-2010 10:50 PM

I can't tell what if anything is under it. But I see no indication of any insulation at all. I'm wondering if I could remove the register in the room and slip something past the duct to reach that panel so that I could push it down.

I don't know how much that siding overhangs I will measure it tomorrow. I am in the Chicago area so it does get pretty cold.

burnt03 09-13-2010 07:51 AM

Quote:

Originally Posted by Scuba_Dave (Post 500201)
Do you know if there is any insulation in there ?
How far down does that front siding hang down over the plywood?
I'd be inclined to put up 1-2" rigid foam then another piece of plywood
Put a piece of trim on the very front if needed to hide it

I might even box off between the 2 beams & add R30

I've got a similar setup at my house, where the overhang extends from the crawlspace and there are chunks of fiberglass insulation stuffed in the voids.

If boxing in below the area, would vapor barrier need to be installed?

Scuba_Dave 09-13-2010 08:00 AM

There will usually be a vapor barrier on the insulation facing the warm side
Then on the outside usually building paper/tar paper before finish siding
So as long as you aren't adding another layer...then yes
Problem is verifying if these 2 layers already exist




Gary in WA 09-13-2010 02:02 PM

I'd add 2" XPS tight to the floor above. Add roxul insulation batt, unfaced (no air spaces), then a layer of foam (and canned foam the joints), and plywood , caulk all ends. No paper as the ply serves that purpose.
http://www.buildingscience.com/docum...n-crawlspaces/

Gary

Hurriken 09-13-2010 04:20 PM

What is XPS?

Gary in WA 09-13-2010 04:33 PM

Second one listed: http://www.energysavers.gov/your_hom.../mytopic=11620

Gary

Hurriken 09-14-2010 10:08 PM

Banzai!!! So today I said the heck with it and I went out and cut into it. There is insulation but it is the same stuff they put in the walls and it was bunched up. It is less than 4 inches thick. The beams are 2x6's.
http://img.photobucket.com/albums/v4...Y/DSC_0763.jpg

What worries me is that it is open going into the house. Notice the line with the glue drip on the left? that is where the overhang starts. the bedroom is behind above this. And the family room is below it.Shouldn't that be blocked off?
http://img.photobucket.com/albums/v4...Y/DSC_0765.jpg

Where do I go from here?

Gary in WA 09-14-2010 11:44 PM

Yes, at least around here we have to: "Solid 2X nominal blocking is required at ends of joists and over all bearing points. Blocking may be omitted where ends of joists are nailed to a header or rim joist." You may have gotten by because of the second sentence.

I would add some rigid foam board as vertical blocking just over the wall. Fill as mentioned before. Caulk under the new ply on the joist bottoms try to air seal the ply similar to: http://www.buildingscience.com/docum...wall-approach/ Add rim foam board to the cantilever: http://www.rd.com/57548/article57548.html
Plug any wiring holes to above exterior wall.

Gary

Hurriken 09-15-2010 10:48 PM

Quote:

Originally Posted by GBR in WA (Post 500448)
I'd add 2" XPS tight to the floor above. Add roxul insulation batt, unfaced (no air spaces), then a layer of foam (and canned foam the joints), and plywood , caulk all ends. No paper as the ply serves that purpose.
http://www.buildingscience.com/docum...n-crawlspaces/

Gary

Isn't Roxul insulation more for fire and sound proofing? If I have this straight I should use 2" XPS to "box" off the openings where the overhang meets the wall. Then add a layer of unpapered batting. Followed by another layer of foam(2" again or is 1" OK) and capped with plywood. It had 3/8" plywood and it just so happens that I have two brand new sheets (my Dad was throwing it out) in my garage.

It's a bigger job that I was expecting but I'm glad I'm tackling it, it should make my house better in the winter.

One more question, look at the 2nd to last picture. That piece of batting goes back into the house. Should I cut it off or roll it back inside?

Gary in WA 09-16-2010 03:55 PM

Glass batt is ok. The foam as you said if fine. If a finished basement, the batt doesn't do much good in the room's ceiling, use it at the cant'.

Gary

Hurriken 09-18-2010 09:17 AM

A few more things as I get going.

The Joists are 2x8's and not 2x6.

I understand sealing the blocking foam and I understand sealing the piece that is flush with the bottom of the floor. I also understand adding unfaced batting which I will glue to the top piece of foam. But why do I need a second sheet of foam between the batting and the plywood facing? Will that actually have an effect? I guess that should be sealed as well?

If I understand correctly I should glue the plywood facing to the joists and then seal it with caulk as well? If so it's a one way road. Once I glue that I will never get it off again! No mistakes.

I know there are two heating ducts up there. Should I try to box them with foam or butt up against them and cover them with batting? What can touch the ducting, foam, batting, expanding foam, acrylic caulk? Maybe I can coat them with expanding foam?

Gary in WA 09-18-2010 04:50 PM

The ducts should be wrapped with duct insulation so as not lose any heat on delivery. Just wrap them at the cant'.

Don't glue the ply or even caulk it (sorry), use some sill sealer for the air/thermal break there instead. You want to isolate the cold ply from the joist which would transmit warm/cold/moisture through it.

Gary


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