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WeekEndHack
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# Posted: 10 Sep 2013 22:39
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Just wanted to ping the collective wisdom about shed dormers?
I have a 12/12 roof with a loft floor dropped down 8" from the sill plates and am considering a dormer to open things up a bit and give more light up there.
Never done it before and though it doesn't seem like there's much to it, am I just opening myself up to more potential issues than its worth ...??
Any best practises to adhere to with these?? If I do, was thinking of a 5' high/7-8' long 2x6 wall extension off my sill that I'd attach my rafters off of directly to the ridge.
Steve
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OwenChristensen
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# Posted: 11 Sep 2013 07:22 - Edited by: OwenChristensen
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You didn't say how wide your roof is. As longs as 5' high will give you enough pitch, 4/12 is as low as I'd go. Also what's the rafter span? What size rafter? Are you doing a gable roof on the dormer or just a simple slope from the ridge? There is some weakening in that style, but it should be OK.
Owen
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WeekEndHack
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# Posted: 11 Sep 2013 08:03
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thx Owen.
Its a 16'wide, 20' long.
2x8 rafters, on 16".
shed dormer (not a doghouse/gable) connected to ridge and sitting with ends directly over sills.
What I'm most concerned about is getting the detailing right as I've heard horror stories of getting leaks. I'm starting to think I should skip it given I dont have much time b4 winter to get a roof on (weekend warrior) and I'm working alone. But I'd love to get the extra space as I figure I only have ~6' of space in the middle to walk around up there b4 my head would run into the angled roof walls.
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TheCabinCalls
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# Posted: 11 Sep 2013 09:17
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It is not that complex.
- 4/12 pitch min for shingles (5/12 better)
- step flash the sides
- flash the front if you have an overhang (roof dormer, not wall dormer)
- flash windows
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MtnDon
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# Posted: 11 Sep 2013 09:40
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Look in the library for a book that covers how to build one. Or do an internet search on websites like finehomebuilding, etc. Dormers do make a world of difference for upper space. Building rafters off the ridge to a vertically extended lower floor wall loses no strength. Keep the pitch as steep as you can; no less than 4/12 as has been mentioned. Leaks happen when people do not understand how to flash the wall to roof joint. Shed dormer is easier to build than a gable dormer.
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rockies
Member
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# Posted: 11 Sep 2013 20:19
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http://www.finehomebuilding.com/how-to/departments/drawing-board/designing-shed-dorme rs.aspx
http://www.familyhandyman.com/roof/roof-flashing-techniques-for-outside-corners/view- all
http://www.lifepine.com/PDF/This%20Old%20House%20Article.pdf
These articles should help
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OwenChristensen
Member
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# Posted: 11 Sep 2013 21:12
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All good advice.
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WeekEndHack
Member
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# Posted: 11 Sep 2013 22:49
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thx for this! think I'm almost convinced.
Interesting that one of the articles says one of the biggest issues with these things is people tend to make them too big! You think an 8' dormer on a 22' lenght of roof (5' high) would stick out like a sore thumb. It is running ridge to edge wall. Reduce to 6' ??
Nah, I'm thinking 8' ..
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Sustainusfarm
Member
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# Posted: 11 Sep 2013 23:38
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Here is mine...it was east!
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TheCabinCalls
Member
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# Posted: 12 Sep 2013 12:36
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If you do make it wider make it shorter. This will still let in light and keep it charming.
Also there is a rule of thumb that 70% of a dormer should be covered with glass. That is why most stick out like a sore thumb.
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WeekEndHack
Member
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# Posted: 17 Sep 2013 14:29
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So I've decided on the dormer, anyone see an issue with attaching my rafters to the header of the dormer (w/hangers) as opposed to resting on top.
I've seen a few examples of people doing this though it doesn't seem like it would be as strong?
I'd really like to gain that extra 8 inches to bring my window higher while maintaining the 4:12 dormer roof minimum but I dont want to sacrifice strength either ?
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