Yet again...Another first time TF.

[wabadahabada]

First off, Hello.  I'm here to discuss foundation options for a basic TF shop.

I have chosen to get a blueprint from TimberFrameHQ, The plan I have chosen is a basic (as I see it) saltbox design. (see pic)  I will be doing all the work myself and have quite a bit of knowledge in general residential construction...  

My first obstacle comes in at the foundation. I was planning on a full monoslab, but decided since the TF only makes contact to the ground at 9 points maybe I can get away with pad or post footings.  I realize this will leave me with a dirt floor for the shop and garage, but I can work on this later. (we have tons of large flat granite on site)

Other considerations, last year we had a storm that brought 90+mph winds, snow load is 80psf here, ground gets pretty soggy in the spring, also tends to turn to like a dust if its dug up.  Possible type C soil....

Anyways-if this is a viable option for the TF I have selected, do I just need to calculate the full building load and divide by 9? or are there other considerations I am not aware of yet?

I thank you for your time in reading my post and look forward to your answers.

 

[Ljohnsaw]

The nice thing about pouring a full slab is you will have a clean place to work on and store your timbers...  Looks nice, how big?

I've got moon dust on my property as well.  I went with a full daylight basement (10') since code called for 12' of clearance below the windows for the snow.  My snow load is 315 lb/sq-ft.

[Don P]

If you are getting that kind of wind check your bracing. The knee bracing is light in that drawing but if the building is sheathed in something that forms bracing that would be better, sheet goods or diagonal sheathing.
That roof design does put thrust onto the tall posts and your snow load is substantial, I'd have that checked.

I'm sure you know that pier foundations are an engineer required foundation type. A braced wall over an unbraced pier is simply delivering lateral wind load to the scene of the wreck. Either a continuous perimeter wall with thickened footings at the post locations or a similarly beefed slab is going to perform better but yes ultimately that area under the posts should be designed as post load divided by bearing capacity of the soil. Check each post type, remember your internal posts carry more tributary area and thus load, that is one of the reasons piers tend to settle different amounts over time. From first glance just stuff to mull over anyway.

[Brad_bb]

I'm a fan of doing it right.  These are really engineer questions.  A proper foundation and anchoring for the specific soil, geology and conditions is the most important thing in a build.  Are there county or city requirements where you live? Do you need to submit the foundation design?  You can work with a local engineer or someone like Firetower Engineered Timber.  You have a good frame design, but how it is supported and attached is just as important. You don't want any shifting in the future.  Where I am, we typically pour a footer below frost line and a stem wall. You need an engineer to very the footprint is sufficient for the soil and the rebar plan is sufficient. Having it all tied together helps keep individual points from shifting.  You can use knife plates to anchor your posts to foundation, or timberlinx, or 1/4" plexiglass plates and simpson straps.  I prefer drill and epoxied anchors versus wet set ones like the simpson, because you can lay them out very precisely. When we setting, they never stay where you think you put them. 

[Roger Nair]

Waba, I think the roof system is a risky design that will shift and progressively thrust the front wall outward to a dangerous degree.  I think that a series of posts with a principal purlin could pick up the load and transform the upper collars into a very helpful feature.  Your scarf choice looks good.  You have a problem with tenon interference between the bent girt through tenon and the stub tenon on the wall girt.  My usual solution is to stagger the height of the joist and wall girts with respect to the bent girt.  The giant window opening does not allow for a connection between the end post and the wall.  You might have to in the end fiddle with wall heights, roof slopes and post locations to carry the design off.

[Don P]

I like the purlin idea. Another option on the tenon clash, and the joists, would be Sherpa connectors, or simply set the joists on top of the bent girts.

[wabadahabada]

The nice thing about pouring a full slab is you will have a clean place to work on and store your timbers...  Looks nice, how big?

The design shown is 20x28

If you are getting that kind of wind check your bracing. The knee bracing is light in that drawing but if the building is sheathed in something that forms bracing that would be better, sheet goods or diagonal sheathing.
That roof design does put thrust onto the tall posts and your snow load is substantial, I'd have that checked.

Yes, the wind only got like that for 1 night, some freak storm, but it could happen again...

Waba, I think the roof system is a risky design that will shift and progressively thrust the front wall outward to a dangerous degree.  I think that a series of posts with a principal purlin could pick up the load and transform the upper collars into a very helpful feature.  Your scarf choice looks good.  You have a problem with tenon interference between the bent girt through tenon and the stub tenon on the wall girt.  My usual solution is to stagger the height of the joist and wall girts with respect to the bent girt.  The giant window opening does not allow for a connection between the end post and the wall.  You might have to in the end fiddle with wall heights, roof slopes and post locations to carry the design off.

Thank you for pointing out the flaws in this design with the tenon interference and the lack of connections, I chose this design for is simple box frame, non-complex joints, and the loft space, .... but it sounds like I may be better off going with a more symmetrical design?  one where the roofs joists actually rest on the topplate?  Like a simple gable roof?

I'm a fan of doing it right.  These are really engineer questions.  A proper foundation and anchoring for the specific soil, geology and conditions is the most important thing in a build.  Are there county or city requirements where you live? Do you need to submit the foundation design?  You can work with a local engineer or someone like Firetower Engineered Timber.  

Yes, I do plan to have it passed and verified, but I do live in an area where codes are not really enforced, but with as much work that this will be, its worth it to have some things signed off.  I will look into Firetower, as I have not checked into those services here. 


--Thank you everyone, Spring is such a busy time and I thank you for yours.