stair foundation precast concrete
stair foundation precast concrete
(OP)
we will be using precast concrete instead of cast in place for the stair foundation.
i just said precast concrete in the drawing.
is that right? the contractor will find a precast vendor for this foundation?
i just said precast concrete in the drawing.
is that right? the contractor will find a precast vendor for this foundation?






RE: stair foundation precast concrete
If you are expecting the pre-cast to be designed by others you must provide the applied loads and the intended anchorage of the stair above. I would also ensure that the appropriate foundation design information is there (bearing capacity).
That being said, why? It's much tougher to hit proper elevations and leveling of the block when compared to a cast-in-place option. I fail to see how a pre-cast blob of concrete is a more economical and constructible.
RE: stair foundation precast concrete
Will my drawing work (as far as purchasing this precast concrete block)?
This is just a small stair foundation.
I already provided the rebar and concrete size for the precast vendor.
No need for them to re-design it.
RE: stair foundation precast concrete
The 2' dimension, A.B’s. to front edge of ftg., in front of the lowest tread, is not enough length in the direction of travel for a landing or stoop. Make that dimension the same as the width of the stair treads. So, the ftg. will be about 2' wide, not 3'. Check with the local AHJ, they might hassle you about what you show in your sketch. I agree with Jayrod12. Making that ftg. precast and then trying to place it properly in orientation and elevation, seems difficult to me, in comparison to a cast in place flg./slab, with a couple A.B’s.
RE: stair foundation precast concrete
RE: stair foundation precast concrete
Anyway, I'd favor using something else for the landing and hide the precast grade beam (1'-0" x 4'-0" in plan view) behind the landing. With a nice long threaded rod epoxied in, you should be able to get all the tolerance you will need for final installation. Let the precast sidewalk guy figure out the landing!
Might not need any reinforcement for this foundation.
RE: stair foundation precast concrete
RE: stair foundation precast concrete
RE: stair foundation precast concrete
There's also only like a third of a yard required to pour that. If designed properly (i.e. designed for a low concrete strength) they could probably mix it on site.
RE: stair foundation precast concrete
As for leveling, that can be done with sand or fill-crete. Since the stair has steel risers I would expect the contractor will make up the difference in grout under the stringer. Still seems like more work, but whatever the client wants.
RE: stair foundation precast concrete
We do a number of jobs like this for regions where there is poor access. Shouldn't cost much more for precast vs. CIP to make a difference to the budget.
Professional and Structural Engineer (ME, NH)
American Concrete Industries
www.americanconcrete.com
RE: stair foundation precast concrete
Put more lifting inserts in it, though.
RE: stair foundation precast concrete
delagina - One stupid, simple question: Does this CM have equipment on the site to place a 3,600 lb (2' x 3' x 4' X 150 lb/cf) block of concrete in the correct location?
Seems to me to be a bit oversized at 2' thick.
Ralph
Structures Consulting
Northeast USA
RE: stair foundation precast concrete
The PM may be concerned about scheduling. No waiting for cast-in-place concrete to cure. (not that this is a good reason, just it is a reason)
RE: stair foundation precast concrete
Dave
Thaidavid
RE: stair foundation precast concrete
thaidavid40 - I realize on most normal projects setting a 3600 lb precast element should be simple. But OP said:
If the PM can't get equipment to handle placing about 1 CY of readymix concrete, how will he set a 2 ton precast element? Since we can't see the site or the overall structure from here, it's awfully difficult to judge the logic involved.
Ralph
Structures Consulting
Northeast USA
RE: stair foundation precast concrete
Have you considered the "pushing" load that will be exerted on this small precast slab? The bottom of the stair section will have a relatively high lateral load from the stair loading. This will tend to "push" the slab unless restrained by a walkway or other obstruction.
RE: stair foundation precast concrete
RE: stair foundation precast concrete
Regardless of the relative sizes of the equipment needed to accomplish the two, competing concepts, it seemed apparent from the OP's statement that whatever equipment would be needed to set a precast pad was already acceptable. Otherwise, why the suggestion from the PM to use such? And by comparison, a single heavy fork truck would be much less disruptive than a concrete mixing truck. Therefore, my suggestions for how to handle setting such. I paid no heed to his logic in selecting the preferred option, and therefore judged it not, I only suggested a process to accomplish that.
Dave
Thaidavid
RE: stair foundation precast concrete
Professional and Structural Engineer (ME, NH)
American Concrete Industries
www.americanconcrete.com
RE: stair foundation precast concrete