|
| Author |
Message |
Steelpulse
Member
|
# Posted: 16 Sep 2024 10:52pm - Edited by: Steelpulse
Reply
Hey all read a ton so far very helpful reading as a diy builder.
planning a small build 16x20 with a back loft
planning 2x4 framing
2x6 rafters and 2x8 ridge board (using 2, 2x8x12 ridge boards meeting in the middle)
roof pitch 12/12 no snow, snows maybe once a year if that.
couple questions
if i use 2x8 to span the 16' width would
2x8 loft floor/joist sit on the top plate and attach to the rafter or attach to underside of top plate attached to the frame studs?
can i just have this in the the back half/10' of the cabin will i be able to get away with no collar ties and no more joists in the front half of the cabin leaving it totally open?
thanks i am finally getting around to this project
|
|
Grizzlyman
Member
|
# Posted: 16 Sep 2024 11:37pm
Reply
I think you are asking about floor joists for the loft? Tie it directly to the rafters. They would then be rafter ties that double as floor joists.
16’ is too long a span for a 2x8 floor joist. Will there be a center wall supporting them?
You need ties in the front too. Being as you have no snow/ you can probably get by with a a tie every other or every third depending on how the math shakes out.
I originally didn’t want rafter ties in my cathedral area either on my cabin… but told my wife I can’t fight physics. several years in now it’s not a big deal at all. In fact, they’re nice because you can hang lights and fans etc from them.
|
|
ICC
Member
|
# Posted: 17 Sep 2024 01:52am
Reply
Ceiling and upper level floor joists should sit on the top (doubled) plate. They would be nailed to the rafter tails to form a rigid triangle.
2x8's are barely large enough to support light attic storage loads. Not for habitable spaces.
You should have rafter ties across the cathedral ceiling section to prevent outward spreading of the side walls by the weight of the roof framing materials
|
|
gcrank1
Member
|
# Posted: 17 Sep 2024 02:19am
Reply
Everything is far heavier than I think.....and span tables are the bare minimum.
|
|
ICC
Member
|
# Posted: 17 Sep 2024 03:11am
Reply
I like the AWC calculator as you can specify the species to match what is locally available and adjust loads, spacing, etc.
https://awc.org/calculators/span-options-calculator-for-wood-joists-and-rafters/
Webpage as well as Android and iOS versions.
|
|
Brettny
Member
|
# Posted: 17 Sep 2024 02:03pm
Reply
https://www.blocklayer.com/roof/raftereng
Use the after calculator to figure out head room in your loft. Alot of it is going to be less than 6' and not really useable. Have you thought about a gambrel roof? You gain alot of head room.
To awnser your question no you cant leave the the 10' section of ceiling with no wall tie or floor joist. I believe you want to have half of the cabin to have a cathedral ceiling? You really need something to tie the walls together even if it's a single board/log in the middle of the 10' cathedral section. That is unless you lower the ceiling way down to below the 1/3 section of the rafters.
|
|
|
