Need a little advise and some comments

[beetle]

I will begin putting in the foundation for my timber frame barn shortly and my current plan is to make my frame 1/4" wider than the foundation in both directions. This will provide me a 1/8" tolerance all around so my vertical siding will clear the block nicely when I overlap.

suggestions and/or comments? Is there a rule of thumb for this?

As always...Thank you!
Jeff

[Jim_Rogers]

beetle:
May not be enough.
How are you doing the foundation? Poured concrete wall or hand stacked blocks?
Getting the foundation crew to pour a concrete wall to the correct size and that close to size will be a challenge.
If they are under size, it's not big problem as you'll just have a little more over hang, but if they're over-sized what are you going to do?
How are you going to fasten the timber posts to the concrete foundation?
There should be some type of moisture barrier between the concrete and wood, so that the wood doesn't wick up the moisture and rot.
Jim Rogers

[Jim_Rogers]

Also, as this structure will be putting a point load on the spots where the posts sit on the foundation wall, of either type, these points need to be reinforced with steel re-bar.
For wind hold down, metal straps can be attached to the re-bar and stick up threw the surface of the foundation wall for attaching to the post bottoms.
If you need a detail drawing of this let me know and can scan one in, or draw one and email it to you.
Jim Rogers.

[beetle]

Jim,
The foundation will be block reinforced at the point load areas. Do you thick 1/2" oversize which will give me a 1/4" tolerance?

[Jim_Rogers]

Are you personally going to set the blocks?

And in regard to the oversize do you mean the frame? I'd assume so, as you want the foundation under sized.

If you or your block setter can hold to tight tolerances then 1/4" frame over size or 1/4" foundation under size will be fine.
You could always fill this gap in later with something to stop any pests from entering your frame/barn from underneath, such as caulkings or metal flashing, or just a small piece of wood.

Good luck with your project.
Jim Rogers

[ARKANSAWYER]

Jeff,
  I always consider the way the frame is tied to the foundation to be more important than any thing else.  I have seen frames put on pads and it break and cause the frame to sag.  I have seen blocks sink in the ground after a freeze and a frame sag.  I like re-bar and thick edges under my frames.  I do not worry about how much my frame or siding sticks over the pad as I have it tapered away some at finish.  I anchor my bottoms well and seal my post ends with linseed oil well before installing.  Good over hang and splash control is the best to keep your siding sound and looking good.


  The best frames I have seen were old and they got that way because they set on solid ground and water was kept off them.  On most frames you need not worry about 1/4 inches just feet.
ARKANSAWYER

[beetle]

Thanks Arkansawyer,

Anchoring the posts to the sill and the sill to the foundation is a big concern of mine also, I want it right and tight.

My footer will be 42" down in old mother earth, 16" wide X 10" thick, reinforced with rebar at the post locations. Four coarses of 8" X 16" 41 pound CMU block poured solid three blocks wide at the post locations. 5/8" X 17" long galvanized structural anchors with 58,000 psi tensile will be placed in the CMU on both sides of each post location and one dead center between each post to anchor the sill to the foundation.

That is my plan for the foundation and anchoring the sill to to the same. I am still debating on how I am going to anchor the posts to the sill plate. My wife and I do not want to see steel plates at the bottom of the posts. In addition,  I am not a big fan of USB straps.

My sill is 4" X 8" pine, one thought is to recess 1/8" - 3/16" plate on the exterior side of each post bottom and sill and screw in place. Any  comments and/or thoughts is welcome.

Jeff