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I AM INSTALLING A 2 POST AUTOMOTIVE CAR LIFT IN MY GARAGE AND WOULD LIKE TO POUR 2 NEW SLABS FOR WHERE THE LIFT WILL BE ANCHORED DOWN(APPROX 3FT X 2FT) I HAVE 4IN OF EXISTING CONCRETE, ABOUT 5 YEARS OLD. I CAN HANDLE THE CUTTING AND DIGGING, BUT I DONT KNOW MUCH ELSE. CONCRETE NEEDS TO BE AT LEAST 300PSI. THANKS DAN BROWN XXXXX@XXXXXX.XXX

Submitted: 18 days and 22 hours ago.

Category: Home Improvement

Value: $15

Status: CLOSED

Posted by Rick 18 days and 19 hours ago.

Answer

Hi dan

You mean the concrete needs to be at least 3000 psi. You should make your footings at least 2' x 2' and 12" thick. In the footings you should put 2 layers of 3/4" rebar in a checkerboard pattern with the squares ~6" square. Try to determine where your bolts for your lift will fall so you can avoid putting rebar right where the bolts will go. You might want to set the top of the footing even with the bottom of your existing slab so you can pour a finished slab on top.

18 days and 18 hours ago.

Reply

What I really need to know is the type of cement, and if I should put some form or expansion material around the outside between the new and old concrete. And should I drill into the old cement and rebar it to the new?

Accepted Answer

The footings I described should not need to be connected to the existing slab. Be sure to set your footing on undisturbed soil. You don't need an expansion joint but an expansion joint will stop the rest of the slab from cracking if your footings settle. Sakrete high strength concrete mix (I'm assuming you are going to mix this by hand) will give you 2500 psi after curing for 7 days and 4000 psi after 28 days. Of course if you are getting ready mix delivered (this won't meet anybody's minimum delivery) you just tell them what strength mix you want. If you don't want to wait 28 days (actually more like 14 days) then you would need to use Sakrete 5000 plus which would give you 3500 psi in 7 days but this product is much more difficult to find. If the soil these footing are sitting on is at all questionable then increasing the size of the footings to 3' x 3' or larger may be necessary. 3' square footings should be more than enough for most circumstances.

Accepts:
Expert:	Rick
Pos. Feedback:	100.0 %
Answered:	11/2/2009

General C&ontractor

Licensed Construction Supervisor & Remodeling Contractor 35+ years experience

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