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I'm adding a screened room onto the house. The roof will be perpendicular to the house roof with the same 5/12 pitch. I would rather use rafters than trusses so the ceiling will be vaulted for a better look. I have built a barn and a workshop using trusses, but I've never built anything with a roof using rafters. I think I can do it, but I'm a truck parts salesman, not a builder. I'll be doing all the work myself. Do you all know of any problems I could/will run into?
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What is the span?
You will need a structural ridge beam or else some form of collar tie to keep the rafters from pushing the walls out.
If a structural ridge beam we will need the length of beam also. Last bit of info is the roof loading for your area.
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I assume the rafters will go up the roof to the existing ridge.This means you need two 2x 8 or wider plates that nail to the roof . Shingles under the plate must be removed and reinstalled with flashing after the roof is sheathed.Each pair of rafters going up to the peak will be shorter by the same amount til you reach the last pair.
There is a lot more to consider,if I were you I would hire a carpenter that is a roof framer to help you.Make sure if you do hire someone they know roof framing,not all carpenters are capable if they haven't done it before.
You will save your self a lot of headaches and problem a few dollars in material too.
mike
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The ridge beam will be 28' 8". I don't know the roof load. I live in TN, and we don't get much snow here.
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What is the rafter span or width of the room?
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mike4244 said:
I assume the rafters will go up the roof to the existing ridge.
The "perpendicular" comment would preclude this.
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Perpendicular is at right angle to the main roof. Parallel, is I assume what you were thinking.
I have framed a few roofs in my time but not considered a roof framer.
I have framed exactly what the OP wants, several times. Not as simple as a straight gable roof that does not tie into the main roof.
That is why I think he should hire a roof framer for a day.Once the roof is framed he can sheath and shingle it himself.
mike
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I am assuming the ridge of the new addition would be perpendicular to the ridge of the existing roof. Thus the roof loads would be carried by a ridge beam with one end supported by a post in the existing wall and the other in a new wall away from the existing. The lower ends of the rafters would be supported by bearing walls. If the OP has other plans then he better describe them better.
A 28' ridge beam span is pushing what you can find in a manufacturers span table so the local authority will probably require a structural engineer size the ridge beam anyway.
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The span is 16' and the beam will be 14' 8" from the existing wall to the outer wall. I can splice it on top of the existing wall and extend it to where it will tie in to the existing roof.
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That is easily doable then. The part over the existing roof is called overframing and if it will just be attic can be lighter members which transfer the loads to the existing roof below. That part will only need rafters and a ridge board, not a structural beam. So, if the width of the porch is 16' and the length of the beam is 14'-8" then the ridge beam and rafters should be able to be determined by using the span tables from the lumber supplier and engineered beam manufacturer. Contact a decent lumber yard and they will be able to help you find the correct sizes for both the rafters and the ridge beam. Simpson will have information on the rafter hangers at the top and the ties at the rafter bottom. If the work will be inspected by a local authority its always a good idea to run your plan by them and see if they will allow you to use span tables or if they will required a structural engineer to review the design.
This is typically how the over framing part is done.
another view of the over framing part.
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