converting flat roof to pitched roof 1

[cruzinbear]

I am working on a project to convert a residential flat roof to a pitched roof. The home was built in the 1960's and some modifications were made in the 90's. There is no official building plan for this structure.

The existing flat roof is made up of 2x6 laid flat against each other (weak-axis bending). The contractor wants to leave the existing roof and add a new roof frame over it. I want to know what is the most effective way of tackling this project since we are going to be adding additional dead load and since there is no existing building plans to identify shearwall locations. What is the best way to anchor the frame? And, what is the most cost effective solution, while not compromising safety, to ensure proper seismic resisting system?

Any comments, suggestions, and recommendations are welcomed and much appreciate. Thank you.

 

[dik]

Can you put knee walls on the roof and span 2x6 or whatever between them to provide your slope?

Can you put roof trusses in place @ 4' o/c and use 2x6 on flat purlins @6' or so and use prefinished metal rood deck?

Lots of ways to skin this cat...

Dik

 

[dik]

Should have added that the existing roof should be capable of taking the new loads... may even have to stip the original roofing off (recommended, anyway).

Dik

 

[racookpe1978]

Try to add the "new" insulation (over the old roof, if it is not completely removed to save weight!) before laying the new 2x6 across.

What slope does the owner/architect want on the new roof?

 

[charliealphabravo]

A wood truss package would be the simplest way to add a pitch without concentrating the load. I would think it would also be very cost effective on the material and engineering side and would minimize your liability.

 

[msquared48]

I agree a truss package is the best, but maintain the same bearing points (there may be three or more, not just two) as much as possible, use the short wall over the bearing points to raise the roof - a 6X6 may be enough - and do strip the old roofing material off.

Mike McCann
MMC Engineering