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cabinnewbie
Member
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# Posted: 26 Sep 2022 23:17
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All these details about a shed style roof that I'm confused about and not much resources online...
Easy to add a soffit at the bottom side of the roof but what do I do at the peak? Do I try to build another soffit?
I'm planning to put blocking between the rafters at the top plates with a small gap at the top for air. With the soffit, I'm not worried since there will be a screen for bugs. But at the peak, if I don't have a soffit then what happens here?
Or do I only vent the bottom soffit and leave the peak alone?
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DaveBell
Moderator
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# Posted: 26 Sep 2022 23:28
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Vent at Gable ends. Not at peak. Look at link in Fenny's post for shed style.
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Brettny
Member
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# Posted: 27 Sep 2022 09:40
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How small of a opening above the blocking? Theres a spec for how big the opening needs to be for a ridge style vent to work. In this situation your basically going to have a ridge vent, but only be pulling in cold air from below from one side.
What style roofing really matters here along with how much Insulation and what the R value spec is for the climate zone.
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rpe
Member
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# Posted: 27 Sep 2022 10:01 - Edited by: rpe
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I used vented aluminum soffit under both the low and high side overhangs, with a 2" space above the insulation for the vent air to freely flow up to the peak. That's the only way I can see to vent those rafter bays.
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cabinnewbie
Member
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# Posted: 27 Sep 2022 15:27
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I'm in climate 6, VT. 2x10 rafters, metal roofing waiting to be delivered.
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cabinnewbie
Member
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# Posted: 27 Sep 2022 16:23
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Making a soffit at the peak seems really difficult (peak is ~15 ft off the ground).
Other option im considering is cutting my blocking between the rafters down to have 2 inches of space between blocking and sheathing. Then I'll staple insect screen at the top of each bay?
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Brettny
Member
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# Posted: 28 Sep 2022 08:43
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Since you have 10in roof rafters you dont have enough space for fiberglass. Since the roof is going to be metal if you dont have enough or any air leaks condensation will form and mold the back of the insulation and framing.
https://www.energystar.gov/campaign/seal_insulate/identify_problems_you_want_fix/diy_ checks_inspections/insulation_r_values
What type of insulation where you planing?
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cabinnewbie
Member
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# Posted: 28 Sep 2022 19:16
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I was going to likely use fiberglass or mineral wool batts.
If I have the minimial 1"+ (I know the recommendation is 2") air gap between the insulation and sheathing though wouldn't that be fine?
Also planning on having a wood stove so i expect it'll be toasty enough
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DmAK12
Member
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# Posted: 9 Oct 2022 17:58 - Edited by: DmAK12
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You will have adequate ventilation at 1", 2" is just nicer. Use cardboard baffles from lowes to keep insulation out. Continuous ventilation from lower overhang to peak is mandatory or else might as well just build a hot roof. Main concern would be making sure wind driven rain doesn't find its way in through the peak. Put screened vents as far from the intersection of roof and wall as possible to eliminate possibility of rain.
I did a shed style roof but used trusses with a 24" raised heel, so I just used 2x4 blocking at top and bottom of heel, then nailed sheathing over that. Closed in the "soffits" with 1x6 T&G and just framed in some screened vents.
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Brettny
Member
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# Posted: 9 Oct 2022 20:31
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Quoting: cabinnewbie If I have the minimial 1"+ (I know the recommendation is 2") air gap between the insulation and sheathing though wouldn't that be fine? Also planning on having a wood stove so i expect it'll be toasty enough
Yes you will be warm enough how ever it's not about that. With poor insulation and poor venting you get warm air leaking up through the insulation and causing condensation on the bottom of the roof. With poor venting it will cause mold.
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Aklogcabin
Member
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# Posted: 10 Oct 2022 10:41
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I'd say you're doing good. Sounds to me like you're going to have a gap at the top ridge of your roof. An exhaust air gap created by leaving a 1-2" gap in ridge. As suggested by installing the inserts that staple to the plywood roof material you will have an air gap to carry air from the bottom soffit to the ridge on top.
If using a metal roof a rain cap on top is all you need. There are foam inserts that can be installed in the gaps for roofs with a 3/12 pitch or less.
As for your soffit question on a shed roof. Screen off the gap at top. The edge or gable end trim pieces used with metal roofing should work fine.
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Brettny
Member
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# Posted: 13 Oct 2022 06:10
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Here's a taste of what can happen if you dont Insulate properly. Also this is a video of a rim joist not the worst area of a building, the roof/ceiling.
https://youtu.be/CbC4bZi2ozk
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Tim_Ohio
Member
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# Posted: 13 Oct 2022 09:39
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Would ideas in this drawing be of any help? Perhaps the top flashing could be set out a bit and the top of the sheathing cut back an inch to allow air to flow up and out through convection current created below at the vented soffit. Since the ribs of the roofing are gaps at the top, they would allow air to pass if the sheathing was opened up an inch or so at the peak/top underneath the roofing. I dunno if my idea is clear or not. That top flashing could be removed in the future to inspect for potential problems or to see that nothing is going wrong?
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Tim_Ohio
Member
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# Posted: 13 Oct 2022 09:49
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Or, I suppose some openings at the top of the top fascia board could be drilled holes or cut slots to allow
air to flow out under the top piece of fascia flashing. You could easily staple screen across that, before installing the top angle flashing. If you want the face of that flashing to sit nice and pretty across the length, you could add some small block supports every foot or so. Just some ideas. I dunno.
Tim
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