I have created a situation that I need some advice. I am timber framing a screen porch on the back of my existing 2-story house. The overall dimension is 14’x30’6”. I would like to keep the main girt (30’6”) of the outside wall at least 9′ above the deck. I would like to stick with traditional methods but am not opposed to nailing or straping something as a last resort. I am building on a slab that has bolts for the bottom plate(2×6) and straps for each post(6×6). These will be concealed in a 3′ knee wall running between the posts(7′ on center). Also, the 6×6’s and band board (3×12)will be bolted to the house. The problem comes from a window on the 2nd floor. In order to keep the roofline below the window (and the girt 9′) I will have to go with a rubber roof on a 1-12 or possibly 2-12 pitch with the top of the rafter(3×8) flush to the top outside corner of the girt(6×12). I had planned to cut a full(3”) dovetail mortise at the head,notching the bottom 4” of the rafter, so the dovetail would be 4”. The tail of the rafter I plan to cut like so…shoulder the full 8” 1 1/2” into the girt then come up 4” and notch the tail the remainder of the length so that I have a 16” overhang. The girt will then have a 3”x4”deep notch at each rafter(the rafters being 2′ on center). The rafters will have an aprox. 14′ inside span. We live in Charleston,S.C. so I’m not worried about roof loads. Your probably tired of reading so I implore. Is this conceivable? Is there a better method to achieve the desired eave(I would like 2′)? How do I pin the head and tail to prevent up-lift(we do get hurricanes)? Thank you!
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"I have created a situation that I need some advice. I am timber framing a screen porch on the back of my existing 2-story house. The overall dimension is 14'x30'6''.
I would like to keep the main girt (30'6'') of the outside wall at least 9' above the deck. I would like to stick with traditional methods but am not opposed to nailing or straping something as a last resort.
I am building on a slab that has bolts for the bottom plate(2x6) and straps for each post(6x6). These will be concealed in a 3' knee wall running between the posts(7' on center). Also, the 6x6's and band board (3x12)will be bolted to the house.
The problem comes from a window on the 2nd floor. In order to keep the roofline below the window (and the girt 9') I will have to go with a rubber roof on a 1-12 or possibly 2-12 pitch with the top of the rafter(3x8) flush to the top outside corner of the girt(6x12).
I had planned to cut a full(3'') dovetail mortise at the head,notching the bottom 4'' of the rafter, so the dovetail would be 4''.
The tail of the rafter I plan to cut like so...shoulder the full 8'' 1 1/2'' into the girt then come up 4'' and notch the tail the remainder of the length so that I have a 16'' overhang. The girt will then have a 3''x4''deep notch at each rafter(the rafters being 2' on center).
The rafters will have an aprox. 14' inside span. We live in Charleston,S.C. so I'm not worried about roof loads. Your probably tired of reading so I implore. Is this conceivable? Is there a better method to achieve the desired eave(I would like 2')? How do I pin the head and tail to prevent up-lift(we do get hurricanes)?
Thank you!"
C-Con,
I think I would only notch the rafter bottom 2" at the head. Cutting 4" out only leaves 3 1/2"- 4" of meat to carry the load and I fear the rafter splitting at the notch.
Other than that, I like it.
You should be able to use diagonal pinning, either down from the tops of the girt and band keeping them hidden, or from the sides to show them. I would only try to get about 2" penetration into the rafter with the pins in either case. I see no need for the pins to be any deeper than crossing the joint and I feel better by not drilling all the way across the rafter.
Thanks SamT. I talked to some folks here with some post and beam experience and I think we've hashed out some questions. No problems, just opportunities, right? This is my first time working with timbers so I'm constantly asking questions. Hope it's not my last though. appreciate the comments. C-CON Helping build God's Kingdom on Earth.