Masonry Building Question

[bridgebuster]

My parish is going to solicit bids for the demolition of a two story masonry building. I'm helping out with writing a scope of work and preparing information for bidders. The building was constructed in 1969 but there are no plans available; so I've had to do some minor demo on my own. Here are some particulars:

115' x 45 in plan, approximately 18 feet in height. The exterior walls (from grade to top of seconf floor)and interior bearing walls are 8x8x16 CMU.

There is a 20 x 72 basement; the walls are 8x12x16 CMU.

The second floor deck and the first(ground) floor deck over the basement is 6"x16" precast concrete plank with a topping.

Two questions - I'm hoping to avoid getting out the sledge hammer, pick, and shovel:

My guess is that the entire first (ground) floor is precast plank and not a combination of plank and slab on grade; in order to avoid differential settlement.Is that logical?

If most of the first floor is slab on grade, would you construct a perimeter wall about four feet deep (this is NE Pennsylvania) to support the exterior walls or just thicken the slab on grade? I'm guessing an 8" block wall on a 12 x 24 concrete footing.

 

[csd72]

could be any of the above, I have never had an existing building that was exactly as I expected.

Us structural guys are pesky critters, we all have our own different ideas on what will save the client money.

No substitute for intrusive surveying.

 

[BAretired]

My guess would be...precast planks over basement, slab on grade elsewhere.

You would need a wall extending about four feet below grade to prevent frost heave.

Best regards,

BA

 

[hokie66]

Yes, I agree with BA. Unless there is a crawlspace under the ground floor, and you should be able to tell, I doubt that precast planks would have been used for that part. Might have made good sense to do so, but I still doubt that it was done.

 

[bridgebuster]

There's no crawl space. An odd thing I noted: this was originally built as an apartment building and the ground floor units have a 12" thick patio slab.

I guess I can sledge hammer some of the topping to satisfy my curiosity. Thanks for the opinions. We're going to let this as a lump sum job but I just want to give bidders as much information as possible.

 

[BAretired]

Probably not a 12" thick patio slab. More likely a four or five inch patio slab with edge thickening to 12"

Best regards,

BA

 

[beton1]

You might want to drill some holes in the patio slab to confirm thickness. You could also dig a test pit beside foundation wall. Agree with what is said about 'likely' construction. Is the basement accessible?, look for any duct/service lines. As this is a parish/church/non-profit, it would be hoped that demolition/contractors would give the organization a fair shake when unexpected conditions arise.

 

[darthsoilsguy2]

if you're demo work is to put another building in it's place, make sure the contract has an unsuitable soils allowance that gets credited back if not used for areas approved by the owner.

 

[csd72]

Is any of it suitable for recycling.

The brick and concrete could possibly be crushed on site to use as hardcore under the slabs or just to fill in the basement.

The environmental aspect may win votes with the school.

 

[bridgebuster]

In this state, brick, block, and concrete can be crushed for use as "clean fill" provided the material meets DEP requirements.