Looking at putting a 4-post lift in the garage. Just using BenPak an example.

Garage floor (per local codes at time of construction) is thick enough per the lift web site I've been looking at. I can drill few test holes and check it.

The floor does have some cracks in it and a small part right next to the basement foundation/wall at the edge has heaved up about 1/2" in a maybe 6" x 6" area on the floor. The lift would be in the opposite garage bay. Cracks are all pretty small (no huge gaps or anything, could maybe fit a paper clip into a crack).

The lift installation instructions state to not put it on any crack or near any cracks but I'm not sure I can avoid that completely.

When I add up the weight of the lift + car (4,000 lbs) it will be distributed over 8" x 6" floor base plates, which is far more surface area than a tire contact patch for a basic F150 (4,700 lbs).

If I add in the car parked underneath the lift + lift + car on lift weight, its about the weight of an F250 (6,700 lbs). I would not hesitate to park an F250 in my garage and worry about the floor cracking or failing.

Thoughts? Can I put in the lift, anchor it down and not worry here?

Alternative is to cut up 24" x 24" sections and pour in a 12" deep 3,500 psi concrete patch with rebar (this is the recommended footing per the lift web site). This would be a huge PITA to DIY as I don't have a trailer or vehicle to tow a mixer to the house (need one big enough to mix enough for a single footing, don't want to do multiple pours on a single footing). That and I'm not as into back breaking work as I used to be.

I'm not a construction bro, but I do a lot of load spreading (fify protected) in my line of work.

What about using steel plates to further distribute the load?

silverado_lover said:

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I'm not a construction bro, but I do a lot of load spreading (fify protected) in my line of work.

What about using steel plates to further distribute the load?

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I didn't want 1/2" thick steel plates sticking out around the edges of the lift causing a trip hazard and generally getting in the way.

I think it would be less of a concern with a 4 post lift and the mfr is going to CYA with respect to cracked concrete.

I would drill a few holes to check thickness for yourself and then do a layout of the posts to see where they would actually sit and make a judgement call.

Even if you have to saw out and pour some footings, you're only looking at roughly 8 bags per hole. Easy enough in a wheel barrow or a mixer rental from HD. Plus you could set some templates and anchor bolts to have a legitimate footing.

I am sort of a construction bro. Assuming you have at least 4 inches of concrete and that corner of your shop/garage isn't hanging over a cliff, I don't see an issue with a 4 post.

Almost every failure of a lift I have seen has been a two post ripping out of the concrete because of overload/load balance issues. One was a cool because they left a sledgehammer under one of the arms and as the arm was coming down it lifted that upright out of the concrete. Hilarious because no one was hurt.

I am not a PE btw, so just my two cents.

IntensivePurposes said:

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I am sort of a construction bro. Assuming you have at least 4 inches of concrete and that corner of your shop/garage isn't hanging over a cliff, I don't see an issue with a 4 post.

Almost every failure of a lift I have seen has been a two post ripping out of the concrete because of overload/load balance issues. One was a cool because they left a sledgehammer under one of the arms and as the arm was coming down it lifted that upright out of the concrete. Hilarious because no one was hurt.

I am not a PE btw, so just my two cents.

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yeah, that's what I'm thinking. Just think about the lb/sq.in. from an F250 and it would far exceed the lb/sq.in. on the base of a 4-post lift. I don't think the F250 would cause my floor to fail.

I agree it should be fine. I wouldn't worry about it failing with small cracks. There shouldn't be as much lateral force on a 4 post as there would be on a 2 post.

If you decide to go the crazy tear out route let me know. I have pretty much all the tools and vehicles to accomplish it.

Don't worry about the cracks in the garage floor. The top of the 4 posts are basically tied together by the ramps when your car is lifted so your problem post won't tip over. And unless your floor is loose gravel, you're not going to have to worry about the base kicking out. Anchor bolts have huge shear strength.