More Pier Foundation Questions

[JeffC]

I didn't want to hijack the last post, but on a related issue, are there any alternatives to the use of Simpson (or USP) EPB post bases (or similar) to tie a built-up beam to a concrete base?  I will be building a 16x20 cabin on sonotubes, and will use a built-up pressure treated 3x 2x12 for the side beams.  In lieu of the Simpson bases, which require the use of spacers to fit right, could I simply use a long piece of 1/2" or 5/8" HD galvanized threaded rod embeded in the post and then extending up through the middle 2x12, which would be pieced out (thereby avoiding the need to drill a long and straight hole)?  My outer and inner 2x12's would be full length, and the inner 2x12 would be pieced out with a small (3/4") gap. Any lateral movement (side to side) could be eliminated by pouring epoxy around the through bolt once everything was lined-up.  Any thoughts on this?

[Kodakjello]

Hey JeffC,

I'm building on 12" sonotubes myself and I think you should stick with a pre-fabricated beam bracket. The bracket will provide much better uplift resistance, better connection to the concrete, and better resistance to twisting and racking. Especially if you oversize the bracket. Try looking at the CB66 from Simpson Strong-tie. I'm using those for my porch piers. All you have to do to avoid using shims is place appropriately sized pieces of PT plywood between the 3-2x12's. This will greatly increase the strength of your beam and fill out the bracket properly.

In fact, I upgraded my main house foundation beams (keep in mind this is a 1-storey house so it's completely over-engineered) to 4-2x12 with CB88 brackets. It's 7.5" wide so 4-2x12 and 3-1/2" pieces of ply will fill it up nicely. In the end, it will cost me an additional 6 2x12's and an additional $30 per bracket at most. The original EPB brackets would have given me 24,000lbs of uplift rating....more than enough to make it safe. The uplift rating for the CB88 is 6650lbs which gives me about 106,400lbs of uplift resistance...yumm!  8-)

Shaun

[glenn-k]

Are you dealing with a building department on plans and permits?  It sounds like if you cut down the center 2x as you are talking that you wouldn't have much hold down strength left.  It could be important in high wind or earthquake situations.

[jraabe]

Whatever you do for the bracket you want good solid bearing and uplift protection. I don't like the idea of drilling the beam.

However, you could make the top flat on the concrete pier and cast in a couple of galvanized metal straps. Then put a moisture break such as an asphalt single under the beam and wrap and nail the straps for uplift protection. This is not as good as the brackets and will not have as much resistance to sidewards movement.

Also, you will have to have the top of the piers exactly right or you'll end up shimming things. The metal brackets can be attached to the leveled beams which are temporarily supported while the piers are cast around the bracket bottoms.

[skiwest]

I'm thinking , well doing, the same thing.  Without a sketch its hard but.  I looked at some of the brakets at HD and wasn't impressed so I came up with this .  Using 36" long threaded rod, 1" in corners and 3/4" every where else.  At least 18" inbedment in 12" piers with a 2x2x 4" long angle iron with two nuts set into conctrete.  Top of peir 36" above grade, have rebar in pier 3x 1/2" or 4 x 3/8".  Godd 12" of over lap between rebar and rod.

The treaded rod will allow for height adjustment at construction and later.  Will put 1/4" thk steel plate under and another one on top of beam.  I'm using 4 - 2x12" for beams (3 at 9' centers) .  What I was thinking of doing rather then drilling I was going to drill through some 2x12 off cuts  24" long and attach 2 2x12s to each side.  This way I don't have to drill much of a clearence hole and the hole won't effect the strength of the beam.  between piers would put in 2x10s or 8s every 2 or 3 feet.  More work but beam will be stronger and wider base for joists to sit on.

I really don't see a problem with what is proposed as right above the pier is where you are supposed to do slices anyway as that is where the stress is the least.

[bartholomew]

For the threaded rod, try to get grade 8 steel for the rust resistance. You probably won't find that the big box stores, but industrial supply houses carry it. Grade 5 would be adequate if getting larger sizes.. 3/4" and up.