Roof over existing deck


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Old 08-22-22, 12:16 PM
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Roof over existing deck

Hello. We have a 12í deep by 30í wide deck on the front of our house and Iím in the process of adding a roof. Iíve replaced all the 6x6 posts that were along the front of the deck so the roof supports go all the way to the ground. They are part of the railing. This will be a lean too roof attached to the house. My questions are;

1) This will be a very shallow slope. Maybe a 2/12 or even 1/12 if I can get away with itíll. Iím in NW Arkansas so snow load isnít a major concern. Just enough to shed water into the gutter that will installed. Is that an issue?

2) when I cut the lap splice into the top of the posts to support the rafter beam, is it best to have the cut facing the house or away? Seems like it would be stronger to have the remaining 6x6 material on the outside.

3) birds mouth cuts. Is that necessary for this project? I do plan to use hurricane ties and Simpson structural screws everywhere.

4) is it needed to cut a space for the purlins or can they sit on top of the rafters? Iíve been told to cut out a notch that the 2x4 purlin can set down into is significantly stronger racking wise and we do get some strong winds, but plenty of houses donít do that and they donít fly away.

thanks for the help.
 
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Old 08-22-22, 12:58 PM
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1. With a pitch that shallow you probably need a membrane, hot mop or other type roofing intended for flat or slightly pitched roofs. Most traditional shingles and even metal roofing needs a minimum of 3 or 4:12 pitch.

2. It doesn't matter as long as the beam is fully supported by the column/post.

3. That depends on how you frame it, but bird mouth cuts are not specifically required by code.

4. Avoid drilling holes or cutting notches in rafters & joists. Purlins and roof battens are typically installed on the surface.
 
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  #3  
Old 08-22-22, 05:52 PM
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Thanks for the reply Pilot Dane. This roof wonít have plywood decking, itís just rafters and purlins with metal.
 
 

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