Building the 10X20 shed and have broken my questions into a couple of messages….
I’d like some advice on roof framing. Planning on a gable roof and my questions are:
1) Whats the best way to determine the appropriate slop/pitch/angle for the the roof? Northern CA location…so no snow/load issue….concerned about the aesthetics?
2) What’s the most economical and easiest way to frame the gable roof? What dimentional lumber should I use?
3) If I use a ridge beam….does it need to be something alike a 2X?X20?
4) Is there an easier way to tie the rafter to the cap plate than cutting/knotching the rafter with a “birds mouth cut”.
No more question for a while.
Replies
Unless you have some building experience under your belt, framing a roof can take a lot of time. There's a lot to the figuring of all the cuts and such, plus working with all those loose pieces in the air. I'd recommend trusses.
Even experienced builders use trusses because it's so much less work.
An advantage of trusses is that the supplier does all the engineering for you. You tell them the span, pitch, overhang, etc. They do all the design to local codes. You can have different inside configurations, such as flat ceiling, cathedral ceiling, attic storage, and others. While they're making them for you, you could spend your time doing other things.
Unless you have snow, or some weird local requirement, pitch is a matter of aesthetics. Generally you want it to be consistent with the style of the building itself, with the house, and with the neighborhood.
Depending upon the design, the ridge beam may not actually be supporting much weight. Opposing rafters can be designed to support each other. Many older buildings have no ridge beam at all. Some are still straight, some are not. Many factors to consider. Better to do some research first. Roof load characteristics are more complicated than one would first imagine... I know, it's just a shed, but for the labor and materials invested, may as well spend a couple of extra hours in planning phase to get it right.
They make metal brackets that can be used in place of bird's mouths.
http://www.strongtie.com/products/connectors_list/images/vpa2-2.gif
1) Whats the best way to determine the appropriate slop/pitch/angle for the the roof?
Depends on whether or not there's a ceiling, or head room issues in the shed. If no ceilings, this links to #3 question on the ridge beam. Weather or not you have overhanging eaves will be an issue. Another consideration will be the roof. You want at least a 4/12 fro asphalt shingles (and really shouldn't be under 5/12 at that). For lower pitches, you'll likely need a metal roof of some kind.
Your best bet may be a bit of drafting. Presuming that the shed's top plate is at 8' high, draw a "U" shape 10" wide & 8" tall. Now, sketch in a piths that "looks" right. The pitch will be the rise of the gable end over 1". Say your drawing rises 1/4" in a drawn inch--that's .25 x 12 = 3; then your pitch is 3/12. Knowing the roof pitch will help make a number of furhter decisions.
2) What's the most economical and easiest way to frame the gable roof? What dimentional lumber should I use?
Do you mean the gable wall, or the roof itself? We're back to the pitch, again. A wall only 10' long with a 3/12 end gable would be as easy to build in one piece as any other way. If the pitch is 12/12, a triangular gable wall ontop of the top plate will me easier to manhandle around. The pitch ans overhang will determine the length of rafters used.
3) If I use a ridge beam....does it need to be something alike a 2X?X20?
A ridge beam is very likelt a requirement, especially if there is no ceiling. It will be what ties the two end gables together as well as supporting the roof. (Two purlins will likely be needed, under the roof rafters at their thirds, to help tie roof and gables walls together.) th overhangs used will determine this, too.
4) Is there an easier way to tie the rafter to the cap plate than cutting/knotching the rafter with a "birds mouth cut".
Several. You can cut the rafter flush with the top plate, and extend any overhang with smaller 2x, for one. Simpson makes a rafter to plate connector (http://www.strongtie.com) that may be what you are looking for. They also make a rafter to ridge hanger, as well.
Even a 'mere' 10 x 20 shed has many details to work out--as few as a single-wide, or as many as a 3200 sf custom home.