add on to frame

I just completed the 12x16 frame which is described in the sobon timber frame book and I am already looking forward to expanding on this building. I would like to add a wider section to the end of the bldg. I am thinking say 4 or 6 feet wider at each side and say 8 feet or 10 on the length.This means the front end would be 20 or 24 ft wide and 8 or 10ft in length. This sits in front of the 12 ft wide by 16 ft. length section I just finished.

The shed has a 12in overhang at the gable on the existing roof which has a 1 to 1 pitch. . I was thinking I would go 2 ft higher on the posts and keep the same roof pitch in the addition.Is this addition doable or is there a better way to add a wider section. I am a newbie with zero design skill. Thanks for any advice. Please help me with a solution as I love this stuff.
Bob

I'm a newbie too, but I'll give a little input from what I've seen. A 20 or 24 foot span is doable if the timbers are sized correctly as well as the joints. Ask yourself what the intended purpose is and determine the size you really need. Whether the frame is 24 feet wide or 32 feet wide, it's roughly same amount of work to build. I'm assuming a king post design and that you want to clear span your width. So if you needed or wanted more space, consider that it's just as easy (almost) to up it to 32 or whatever. The tie beam does not have to be continuous with a king post, thus allowing you to use 2 16+ foot pieces for your tie beams, joined to your kingpost. This was the design we used in my recent timber framing class. Our clear span was 24 feet, but a previous workshop did a 32 foot span in the same style.
I'm now wondering how you'd connect it to the other building. It would seem easier to connect a smaller addition to a larger frame as you can just cut mortises in the tie beam of an existing bent and run your girts into them between that bent and the new addon bent. You could also easily add a same size addition onto an exiting bent the same way. Seems a little trickier to add a larger addition on. you may have to remove part of the roof and side walls of the existing and remove the bent (if you need to start the larger addition right at the rear of the existing. Hmmm, that would be somewhat wasteful though...Maybe someone will have a better idea.

Brad,
Thanks for your comments. It is the tieing in to smaller shed that has me wondering. I will wait for other comments from more experienced framers.
Bob

One of the easiest solutions could be to make the second structure a free standing structure that just happens to be adjacent to the first. That is place the posts for the second frame right next to the first frame posts.

What Jim said.

We do this a lot....it is way less problematic and offers a lot more flexibility for planning...often times people want to see full sized timbers in two adjacent rooms as well.... For the most part you are only looking at the additional posts for cost and a little more joinery....

Jim,
Would you recommend to just have a separate door to each structure and no tie in or attempt to tie in with a smaller breezeway(sp?)connecting the two structures?
Thanks for the help.
Bob

That depends on you Bob, you can do it either way.
You can have one common wall with a doorway in that or move them further apart and have a breezeway if you wish.
If you want to send me an email we can discuss your options and I can create some drawings of different ideas so you can understand these options...