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fdecker 11-14-2010 01:08 PM

Open channels down each side of bonus room gable end wall from attic?
I have the typical 2nd floor bonus room with an attic space over it. The end gable wall has a strange soffit-like setup in the attic. After the last ceiling joist that runs parallel to the end wall there is a 5" space. Perhaps this is where the last joist didn't meet up with the end wall? Or maybe this is so that there is space to nail the top of the 6 sided wall board below something?

In any case, the space between the gable wall and the wall to the bonu room below is 2" or 3" lower than the spaces between the celing joists. It had insulation just stuffed into each space created by the studs on this wall, so I removed the batts and sprayed foam in there to seal it. But looking at this wall, at each end, where the roof slants down to become the slanted ceiling of the bonus room there is a vertical channel on each side that has no top plate. There is insulation sticking out into the attic that runs the entire height of the end wall of the bonus room and comes out at the top in the attic. I was sort of shocked. I want to slice off the insulation, cut a piece of foamboard, and caulk it into place to seal those 2 channels. Is this the proper thing to do?

I don't want to seal something that is there to vent stack pressure or something by design. Otherwise, it just seems like a really bad design ;)

Gary in WA 11-15-2010 11:51 PM

A few pictures would help, one from the attic and one from below......


fdecker 11-16-2010 11:38 AM

Argh! I thought people would be familiar with the construction techniques and know what I was seeing. I was afraid someone would ask for pictures. It is very, very difficult getting in there and having to crawl over insulation. There probably is not enough room to take pictures without a wide angle lens attachment. I can try.

The wall below is the end gable wall of the bonus room and looks like every other bonus room ever made. It is a barn shape, a floor, 2 knee walls about 5 ft hight, angled roof, and a flat top:

../................. \
/.... .------ ......\
| ....|..... |.... ...|
|..... -------..... |
|..................... |

I notice the graphics don't take because spaced do not register. Not sure if this forum software takes HTML takes such as (code) to format it. Anyway, pictures coming

There is a window a foot down from the roof. In the attic, looking down at the top plate of the wall, the last ceiling beam does not touch the outside wall. If I lay upside down with my arms up and shoot over my head, maybe I can get an image of the space between where last ceiling beam ends and the outside wall of the house where the channel I'm talking about is.

fdecker 11-16-2010 06:58 PM

Picture of Bonus room and attic above
4 Attachment(s)
Ok, the first picture should be the end wall of the bonus room with a window in the middle of it.

The second picture should be the attic view of me approaching the top plate of that wall. This wall is different than the exact same wall on the opposite end of the attic. On that wall, the last beam is flush with the end of the wall and the top plate is normal. But that wall is a normal straight wall where the bonus room is pitched. Here, there is a sort of soffit arrangment you can see in the next picture.

Next picture shows the view down one of the channels after I removed the small pieces of fiberglass batting that was shoved down there. I am looking down a few inches along the back of the wall to the bonus room. The piece of paper at the bottom of the cavity is backing from insulation under the 2x4 there. I can touch the top inch of the wall below and feel the rough edge of the ceiling gypsum capping that.

The last picture shows the studs for these cavities as they run off to the eaves of the gabled roof. The last channel on each side closest to the roof has no top plates at all. There is just batting stiking out that runs as far down the wall as I can see. You can see the top of the batt in the picture.

I am guessing at this point the the soffit is there because they needed a place to nail the top of the gypsum on that wall and that the voids can be foamed up completely. So I plan on filling those spaces with 6"of spray foam flush with the top of the wood, then cutting the top of the insulation off on the end cavities, making a cap out of foam board, and then using spray foam to seal it in unless somebody tells me otherwise.

Gary in WA 11-17-2010 04:28 PM

The blocking that has been foamed appears to be the header (of two pieces) over the window. The extra cavity between the exterior wall/ceiling is strange. I see the supply flex duct to the room, the chase next to that may be a utility space for ? as they drywall it's lid and ran the room drywall level. This chase required fire-stopping, yet they installed batts there, unusual. I think the apprentice framer installed the ceiling ledger (2x4) too high, top flush with the tops of common joists, not flush with the bottoms..... I would cover the end of the vertical stud bays with foam board or rolled f.g. in a plastic bag to prevent attic air into those wall cavities. Just add higher insulation on the raised chase.


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