Timber Framers Guild

porch design, truss or purlins?

Posted By: deadmancrick

porch design, truss or purlins? - 04/24/07 03:21 AM

I have a new manufactured home (i know i know). It's 30' wide with a 3:12 roof. I want to add a 3:12 pitch covered porch to the front that will extend out at least 10'. Code requires the porch be self supported.
I want the frame to minimize obstruction of the view from the front windows.
And i'm waffling between trusses and a simple purlin type frame. While the post and purlin design would be simple, I'd like to consider some kind of truss.
Any suggestions/links to show a nice low pitch truss?
And lastly, I hope i'm not embarrassing myself here. I'm pretty ignant about this stuff.
Posted By: Jim Rogers

Re: porch design, truss or purlins? - 04/24/07 12:47 PM

One of the first things you need to do is to project the roof line out from the house.
If the house is 3:12 and the porch follows the same 3:12 roof line, how low will the eave be? Of course that depends on how low the house eave line is now.

It really depends on the size of the roof load and the spacing of the porch roof support posts. Most porch roofs usually have posts, say every eight feet or so. These could easily hold up a large timber and the rafters could set on it. With short braces from each post to the beam and with the proper size rafters your porch should look right and be a nice addition to your home.

Just some ideas to think about.
Jim Rogers
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