Hi all,
I have a bump-out on the back of the house with a shed roof that terminates at the wall of the main structure. It has a membrane roof and the membrane runs up under the siding at the back wall of the main structure, so there is no vent for the roof at the wall. I am installing aluminum soffit and called the village to inquire about the venting requirements. They say 1 sq ft of vent area per 150 sq ft of roof area to be vented for a roof with no cross-ventilation and half that for cross-vented roof space.
If it is important enough, I could drill a few holes from the inside out, through the sheathing and the 2×6 ladder soffit board that is bolted to the bump-out. The roof rafters are paired 2x4s, so I could drill below them and still be high enough in the ladder soffit 2×6 to not affect it terribly. The holes would be within the protection of the aluminum soffit and I could also staple screening over the holes to keep the bigger bugs out. I don’t want to drill too many holes, and at no more than 3/4″ or 1″, I’m not sure how much they would help. Any experience or opinions would help.
Thanks,
Scott
Replies
You can buy louvered aluminum vents of various sizes for vertical applications where rain may hit them. The smallest are round, about 3" diameter. Of course there are rectangles too. Pretty easy to install, look OK too.
I'd be inclined, if the village BI is going to insist on vents in exhaust to match with intake (at the sofft/fascia) to just install the "mushroom" vents up near the peak of the shed roof.
I'd match that with a slot in the soffit/fascia area with coravent over that. Mostly as that would be faster than drilling all the holes for the round soffit vents.
Now, how to keep snow from covering up the vents in the winter will likely be an issue. And one never really addressed by code-required venting.
Just one more reason I'm glad I live down here at 29ºN and not 40ºN.
I'd use cora-vent made just for where the roof meets the wall,you then flash on top of the vent and up on the wall behind the siding.
Something similar to what Mike said above, but here is a key question: What is the approximate roof pitch?
Do you need to bring this up to code just because you are giving the soffits a face lift? Either way I'd probably vent the soffits, just because, but going beyond that could be questionable.
As noted, the membrane roof is already in place and runs up under the siding at the wall the shed roof joins. It's too late to install any type of venting stuff at the high point of the shed roof. The roof membrane is glued both the shed roof sheathing and the wall sheathing of the main structure and is not going anywhere. This is why I asked about drilling vent holes beneath the 2x4 rafters, through the sheathing and the 2x6 of the ladder soffit to exhaust into the soffit. To help draw a mental picture, the back wall of the house faces west, and the shed roof slopes down to the west at a pitch of about 1:12. The ladder soffit extends off the north wall of the bump-out. The roof sheathing sits on the 2x4 roof rafters and on the 2x6 ladder soffit. The ladder soffit is attached to the north wall with carriage bolts through the sheathing and the roof rafters. This means the bottom edge of the 2x6 ladder soffit extends 2" lower than the bottom of the 2x4 roof rafters. So I can drill a few 3/4" holes without touching the roof rafters and have those holes vent into the space of the ladder soffit.
"a few holes" are pointless.
2x4's on a flat roof? can't believe that passed inspection so why bother with the venting? fill it full of insulation. yes, that's a choice by code.
i have a shed type roof. i got by without having to vent by filling the space full with insulation[22" deep at the deepest]
one thing about this that has really paid off is,i have a black rubber roof,and that room has always been the coolest. i'd guess the r value into the 50's.
the older i get ,
the more people tick me off