The requirement for Bendpak 10,000 lift is:
Quote:
https://www.bendpak.com/XPR-10-Series-T ... endPak.pdf• Concrete specifications. Make sure the concrete is at least 4.25 inches thick, 3,000 PSI, and cured for a minimum of 28 days. Do not install the Lift on cracked or defective concrete. Anchor Bolts must be more than 6 inches from cracks in the concrete or from a wall.
I would trust Bendpak's requirements. They are well respected. Interpreting your situation based on the Bendpak instructions, a min of 6" beyond the bolt pattern of the lift would be appropriate for the cut. 6 inches beyond the base outline would be better with some margin for error. Dig out 4-1/4 inches below the bottom of the existing concrete. Extend the hole under the existing concrete the same 4-1/4 inches on all 4 sides. That would give you the min thickness for the new concrete under the old with a 45 degree angle of "locking" under the old. I would also wash the underside of the old concrete and spray with concrete bonding adhesive to enhance adhesion. not to mention the previously mentioned reinforcement steel. I would check that the crushed stone base under the concrete is still enough since you are digging out deeper than the original excavation and possibly the underfill.
And wait 28 days for the concrete to cure before drilling and installing the anchor bolts.
So the safety factors are:
1) Sackrete and Quikrete found at the home stores are typically 4000 PSI, Higher PSI can be found.
2) You are using a 7000# lift. The above instructions are for a 10,000# lift
3) Cut 6" beyond the base vs 6" from the anchor bolts
4) The Bendpak lifts are ALI certified. I assume that includes the min installation requirements.
YMMV of course and I have no expertise in these matters. But I would not be concerned if I were installing a 7,000# lift using the above guidelines.
Don't come after me if things don't work out for you using these guidelines.
_________________
Chuck.
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