Question for the Architectural guys (residential side)

[tzframpton]

Quick question. On the PDF that's attached, I'm doing a little modifications for a friend of mine who is using this plan to have a home built. He needs me to recreate this Roof Framing plan but basically I'm taking a few feet off the rear. Anyways, notice around the perimeter of the roof, you see the framing joist and rafters which a number displayed with a feet symbol next to it. I'm trying to figure out what this dimension is representing. This drawing is to scale, and I can't seem to compare the dimensional number to any reference of each joist/rafter. Can anyone explain what these dimensions relate to? Thanks in advance. ;-)

 

Posted this over at TheSwamp.org in case some of you see the duplicate post over there.

7C - Roof Framing Plan.pdf

[Dana W]

Quick question. On the PDF that's attached, I'm doing a little modifications for a friend of mine who is using this plan to have a home built. He needs me to recreate this Roof Framing plan but basically I'm taking a few feet off the rear. Anyways, notice around the perimeter of the roof, you see the framing joist and rafters which a number displayed with a feet symbol next to it. I'm trying to figure out what this dimension is representing. This drawing is to scale, and I can't seem to compare the dimensional number to any reference of each joist/rafter. Can anyone explain what these dimensions relate to? Thanks in advance. ;-)

 

Posted this over at TheSwamp.org in case some of you see the duplicate post over there.

 

That dimension apparently is for material take-off purposes. It represents how long of a standard length of lumber you need in order to cut 'that' rafter from. Framing lumber is sold in 2' increments from 8' to 24' in most areas.

[tzframpton]

Ahhhhhh makes sense. Thanks a lot Dana!!

[Dana W]

Ahhhhhh makes sense. Thanks a lot Dana!!

 

Glad I could help. I have to qualify my post by saying that was an educated guess. That is why I said "apparently". Hopefully someone will confirm it for me. I have drawn hundreds of roof and floor framing plans, but never used that method of dims. Of course, all that drafting work was done for a huge builder of suburban sprawly-ness and they bought all their loose lumber in 16' & 20' lengths by the train load.

 

These dims are convenient and economical for material take-offs, but they also indicate to the framers where the longest lumber has to go, so they don't cut two 9' lengths from the 24' stuff. You can't splice rafters or joists unless at bearing points, and you don't want 300 pieces of 23 1/2" lumber in your dumpster. A competent framing carpenter knows to cut the longest pieces first when possible, I hope.

 

An aside - The most economical per board foot length of lumber is 14 feet long. Shorter stuff is more expensive due to mfg labor and longer stuff is more expensive because it has to be cut from premium logs.

Edited August 24, 2010 by Dana W

[Noahma]

I would agree with Dana, I never do this since about 95% of our homes use engineered trusses now. But that is how we sometimes notate a beam within a floor system that would require a specific length.

[tzframpton]

Thanks for the added clarification, Noahma.

 

You know, I actually have another quick question for an explanation.... What is the symbol that is a circle with two tangent lines coming to a point represent?