Porch to Metal Truss detail

[Crusader103]

Project - Barndominium style home, metal trusses at 12' on center.  Front and rear porch will be open with exposed wood beams.

 

Problem - While I know how to do it (as in build it myself) the builder I am doing this for does not and is requesting a detail as to how to tie in the porch structure to the metal roof/truss system.

 

His specific question is "I need you to show me how that front porch is designed. How is that weight going to be distributed to hold front porch tying back into home. We usually have 12’ center metal trusses for body of home. Therefore it’ll prob be issue. Need it detailed. Thanks."

 

Anyone have a detail they are willing to share or perhaps a better way to do it/express it?

 

Thanks

 

 

19-28 Barndominium.zip

[ShaneK]

How would you do it if you were building it? That's how it should be put on paper. No easy way, cross section with details. Codes might want some engineering on existing roof system bearing the load of the new. If steel truss was in center of each new porch I think that would be structurally beneficial. I see you wood framed existing building, is that the plan?

[Crusader103]

Building it isn't the problem, at least not for me. I know how I would do it. But honestly, I don't know how to create a detail for it for him to do, which is what he wants....essentially how to tie in an exposed wood truss porch to a metal girder roof. I could show him a picture but I'm trying to be a little more professional than that.

 

I've found that CA isn't great at true barndominiums, or at least I'm not as proficient at it in CA.

 

Exterior of building will be wood framed, typical 2x6 with 6x6 posts generally at 12'. That is because he'll be using steel girder type trusses at 12' OC. - I'm still working on getting that down in CA. I do much more typical residential construction than the barndominiums, and each one of those I've done the builder wants different.

 

As for engineering, that's non-existent here. Codes? They don't know what those are here. I'm in south Alabama. It's definitely not like where I designed before (Seattle).

 

 

[Ridge_Runner]

Hi, Joshua. I've done quite a few of these. I guess I don't understand the dilemma. I typically just do a "frame-over" for the porch section of the roof over the house. The main porch roof low side support (LVL's or 2x headers) will be supported by the wall at the house. The truss manufacturer can design the trusses, purlin spacing and the purlin size for the extra roof load and the 12' column spacing. There are several posts on this forum about the "how-to" areas, such as how to construct the purlins from roof framing members and rotated. Once you get the purlins down I would think regular sections would show the needed details. Note: polyline solids drawn in section for the purlins would also work and may be easier for some.
 

I went to the trouble a few years ago to modify a similar truss from 3D Warehouse. I have to modify it for every job as the spans and spacing never seem to be the same from job to job (custom homes always). Once you get one of the half-span metal trusses done, you can mirror it to the other side, finishing the full span. Block those together and then transform-replicate on the 12' centers. I would be happy to send you my "base truss" if you would like. I always modify it in section while it is horizontal (no slope). Takes some math to figure out the final "true-length" of the top cord on your req'd slope (or a CAD detail from view), but not difficult to do. Sometimes a little trial and error but worth the effort to get the visual in the sections.

 

It's not as complicated as my description probably sounds.

 

Hope this helps.

[Crusader103]

Mike,

 

It does help, and thank you.

 

Building it, I would do the typical "frame" over as well. While not an engineer, I don't think the trusses/purlins are carrying that much of a load here. I think the wall and beam at the porch I already have are carrying most of that. Based upon the width of the barndo not being divisible by 12, I actually made a little tighter spacing for the trusses to sit on at the porch area anyway (8' instead of 12').

 

If you're willing, I would appreciate your base truss. Thanks.