Roof Framing

dproc

Framing a screen porch roof. 15' x 24' wide using a micro-lam for ridge clear span 15', 4/12 maybe 5 /12 pitch. All roof framing will be treated for looks (open rafter) thinking of dbl joist for beam effect. Question is- what size lam to use without collar ties and joist size 2x8's or 10's for single or dbl.

Job located in MD

Thanks
Don

Glasshousebltr

Dbl 12" microlam will easily take you to 15ft. I'd go 2X8 on the rafters, your run will end up less than 12ft. Without eve, and a 5/12 pitch, your rafter length ends up at about 13ft from outside wall to beam center.

Have fun

Bob

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Bob

dproc

Something I forgot to mention. The roof will tie into house roof creating a valley. House roof is a cathedral ceilling frammed with 2x8's app. 6/12Thought of stopping lam at house wall (ie 15' CS) continuing with 2x10 (white) ridge or should I use lam entire way to help with load on house roof?
While I wood like to save cost of longer lam I want to be sure of strengthand safety.

pwrbildr

I'd go with the 2x10 on the span from house wall to the house roof. Unless you are going to be adding additional vertical support to the house roof, which would look like hell on the existing cathedral of the house. The span from wall to house roof will be supported by the house roof regardless so less weight in the tie in structure will mean less load on the house roof. Without being there it'd be hard for me to make a recommendation on how exactly to make the transition from the lam beam to the single 2x10.

There is the option of making the double lam beam run continuous through the wall support and catilevering to the house roof. Not sure about the structural integrity of such a configuration though.

Glasshousebltr

The last parts a good option from Pwr. Just make sure you load the lam with a post down to the plate of the house wall. It's good practice to secure solid wood all the way down, inside the existing wall benieth as well.

Bob

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Bob

fettycan

are we building a reverse gable or a shed roof?

dproc

Reverse gable.

fettycan

I think doubleing rafters wood just add uneeded weight and to not use colarties is takeing a chance that it wood push its self apart over time and microlams are not very attractive a truss with a sloped ceiling mite be a better option