Ok to start off, a little about myself. I am a journeyman carpenter with 15 years experience. I specialized in rough carpentry, mainly in residential construction. A couple months ago I had the opportunity to try my hand at timberframe and I loved it. As chance would have it my grandpa's old mobile home had a porch on it that was rotting from the ground up. My dad (who now owns it) and my brother (who now lives there) decided that I should take my new found skills and build a new timberframe porch.
As a carpenter I know or have access to all the local building codes to design and build a new structure using standard carpentry. But with timberframe I am need of some advice.

I am working with a few restrictions.
Keep costs to a min. (So no engineer/architect)
I will be using timbers we have sawn ourselves (woodmizer bandsaw mill) (spruce)
Keep the slope low ish (I'm thinking 5/12)
Display as much timber as posible.
Keep the room free of obstructions (no knee braces protruding into the room.

I am currently away from my computer and typing this on my phone. Once I get to my computer I will post a link to my sketchup design and post snow load info for the area.

The structure is to be 28'8" by 16" with the trusses spanning the 28'8". I have 3 trusses spaced 8' apart. We plan on using either 2x12 or 12"tgi joists 2' on center for the purlins. The roofing hasn't been decided yet but I'm guessing metal. I curently have the 2 end trusses designed as a simple kingpost with webs. The center truss they wanted more height to mount a light or fan from so I made it a scissor truss with an arch cUT inot thw bottoman chord. Both truss types have 8x10 top and bottom chord with 6x6 king post and webs.
I am using 10x10 posts and beams in the walls. 3 posts on each end under each truss. I plan on using standard framed walls to in fill between the posts.

Questions
1. Are my trusses good enough
2. Will the plywood on the infill be sufficient lateral wall bracing.
3. What is the r value of 8" and 10" of timber. (Wondering if I can display the timber inside and out, or if I need to inset and cover with some type of insulation).
4. Will drilling a 1" hole vertical through the center of the ridge and king post affect the structure of the scissor truss.
5 I'm sure as this design/discussion/build goes on I'll have many more questions.

Thx in advance for any help or advice offered. And sorry for any typos, ect as I am typing this on my phone.

Hello Norseman,

I just now finishing a project that would lend itself to you current poarch project parameters, has been PE approved twice, and I also teach timber framing along with other traditional skills. Feel free to send me an email, and we can go into more details of your project, goals in further learning timber framing, and more specifics of your project.

Now, to your current questions:



More than acceptable for a small porch project.



I work in "Asian design" parameters typically so 3/10 to 5/10 pitch is a normal range for "Engawa" and related veranda/porch profiles. 4/10 (22°) is my preferred on most of this type, and almost exactly the same as a 5/12 pitched roof.



Even today, in most Chinese, Korean and Japanese frame modalities the frame is often exposed inside and out, especially in the roof systems. This being a porch, the frame will be completely exposed for viewing. Further, there is not "oblique bracing" in Asian designs, except for some of the "bracketing techniques" in the roof systems, and a few esoteric methods of "oblique bracing" found with "stitch beams," related corbel braces, "horizontal obliques" in the roof and foundation framing (these are always out of the way for normal ingress/egress patters of use) and other unusual methods.

95% or more of the pricing is achieved through proper and specific joinery and "horizontal modalities" such as "Nuki beams." All of this lends itself well to many "modern aesthetics" and not having to contend with "triangles" that can obstruct views, movement, and fenestration withing wall systems.



If you could send that in your email, it would be helpful.



That can get extended to 4 to 5 meter (I work in metric) instead of 2.4 meter (~8") if the design is modified accordingly.



I would wait to see your Sketchup CAD before going into detail on this aspect. I would add here that "2x" stock is not part of typical timber framing for most designs accept perhaps in some of the "Nuki beam" frame work. Most stock ranges from 75 mm x 75mm and goes up from there. The mean average in size is 150 to 200 mm square (~ 6" to 8".)



The post size is rather large and I would only go that big if that is the "aesthetic" one cares for. The "cord" assemblies appear over built as well, unless the lumber is of much lower grade than typically yielded by spruce ssp.



I would have to see the CAD model to address specifics further.

I am sure you will also get much more wonderful feedback here from the collection of members.

Warm Regards and again Welcome to the TFG forum,

j

I wasn't thinking when I posted this that porch means different things to different people. This is to be an enclosed insulated addition (living space) to the existing structure. But built so that if/when the existing structure (mobile home) goes away an new building can be attached/built next to it.

The 2x purlins was simply to create insulation space with minimal thermal bridging. They would not be visible in the finished room.

The 10x10 post and beams were indeed just for aesthetics.

ok I cant figure out how to post my sketchup link. any help would be appreciated

There is no way for this forum to host a sketch up file. If you have a site that can host it and then others can download it, like dropbox or some other file sharing site, then they should be able to provide you with a link if you find a button labeled "share" or something like that.

Once you have the link then there is an icon on the posting form for providing a webpage link. It is the second one next to the smiley face.
Try it and see if you can get it.
Good luck,
Jim Rogers

You can post your model to Sketchfab and put up a link to it:

https://skfb.ly/zHMZ

Or you can host the file on a file sharing service like DropBox / etc. and put up a link.