Verifying an existing footing

[ccvegas]

I have been asked to extend an existing 6' opening in a CMU wall to 12' width. The problem is there are NO drawings of any kind for the building. It is a 15 story block and plank construction hotel that is 36 years old. Verifying the CMU strength and reinforcing is relatively straight forward with xrays and core samples. But the footing is the problem. How to find the size, reinforcing and concrete strength of the footing without totally demolishing the slab and footing. It almost seems as if the resulting gain (larger gift shop entrance) does not justify the means to get there. Any ideas?

 

[concretemasonry]

Are you saying there are no drawings in existence?

For that age and size of building, there should be drawings somewhere to get a permit and build. It just takes detective work and a little time. - Much cheaper than digging and assuming extra liability.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[ccvegas]

Months have been spent trying to locate drawings. There are none to be found.

 

[BAretired]

Assume the worst and provide underpinning adequate to carry the full load. Situations like these are not worth doing expensive exploratory work just to find that you need a new foundation anyway.

BA

 

[cancmm]

To confirm, is this an exterior wall on a low-rise building? If so, why couldn't you make a small excavation on the exterior face if you will likely have to modify the footing anyways?

Probably more to it than this so its just a shot in the dark. Need a little more info