Post base selection

[Arp32]

I've got an interior remodel in construction, single family home with a conventionally framed roof where we're taking out an interior wall below the ridge and replacing it with a glullam flush beam. Loads to 4x6 posts are around 6,500 lbs each. The 4x6's get buried into walls at each end (this is in the center of the home, not an exterior condition).

I do a lot of these kinds of projects, and typically specify a Simpson column base (CB46, CBSQ46, etc...).

The superintendent called on this particular house and of course they forgot to set the base before pouring concrete and now need a post set option (like a Simpson ABU46Z - something with an anchor that can be epoxied in to the footing).

My question is what is your normal thought process when selecting post base hardware for interior conditions like this? I know the ABU bases are good for over 10,000 pounds of gravity loads, but they just feel flimsy to me. Thoughts?



-Jason, Architect

 

[dik]

Any moments?... I've used a single 3/4" dowel epoxied into the concrete and extending into the wood, with a metal base plate to keep the wood off the concrete... worked for years.


Dik

 

[phamENG]

If it's in the wall I don't usually specify one if the wall's bottom plate can support the perpendicular compression and the nails are sufficient to brace the end of the post. Most of the post bases will wreak havoc on the wall finish if you try to use them (I'm guessing this is slab on grade?).

That said, the architect's finishes help drive my decision. As long as there is hardware available that meets the need or it can be reasonably fabricated, I pick whatever will work to get the look right. If it's going to be exposed to the floor and stained, then a concealed connection like Dik's suggestion is a good way to go, or a knife plate with bolts if uplift resistance is needed. If it'll be wrapped and base boards are large enough to conceal it, I'll pick the cheapest post base that will get the job done. I rarely specify the ones that have to be directly set for exactly the reason you just encountered. Most residential contractors can measure, drill, and epoxy a bolt better than they can coordinate its placement prior to pouring concrete.

 

[BAretired]

Do you need a standoff base? If not, why not bear the 4x6 directly on the bottom plate with a nominal connection.

BA

 

[Arp32]

This one wouldn't exceed crushing on a plate, but it's also interior so there aren't any existing anchor bolts nearby.

Maybe I'm overthinking it. The little folded sheet metal post bases just feel flimsy. I guess it isn't going anywhere once the anchor bolt gets set.


-Jason, Architect

 

[phamENG]

You could always epoxy an anchor bolt through the sole plate of the wall next to the post.

They may look flimsy, but they're pretty stout. Of course, it depends on which one you get. They have little light duty ones up to heavy gauge products for large and heavily loaded columns.

 

[XR250]

For that kind or load, I normally use multiple 2x4's bearing on the bottom plate.
I "usually" neglect uplift on structural ridges as, for the short duration, I feel that the there is enough diaphragm stiffness to count on the rafter heel connection to take care of it.

 

[Tomfh]

I just built a new post in my house. 90mm x 90mm. 2.5 tonnes.

Similar scenario. The post bears directly on the bottom plate, with an L bracket each side to tie it to the plate.

 

[Arp32]

I actually went to the house in question today for the special inspection - the ABU46 is beefier than I thought. I probably had those little folded sheet metal fence post bases in my head, the ABU46 is 11GA and the standoff doesn't seem flimsy at all.

Funny thing was, I was there for the epoxy inspection and instead of 5/8" threaded rod or threaded rebar, the carpenters bought 5/8" Titen HD screw anchors. It got epoxied anyway.

-Jason, Architect