Securing a power rack on post tensioned concrete Securing a power rack on post tensioned concrete

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Thread: Securing a power rack on post tensioned concrete

  1. #1
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    Nov 2022
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    Default Securing a power rack on post tensioned concrete

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    Hello everyone. First time caller, long time listener. I've finally gotten around to convincing the missus that not only do I need a power rack in the garage, I need one as soon as possible, because the gym is about to become a zoo with all the post-holiday repenters taking up already sparse rack space.

    I however have one problem. All of the concrete in my house is post-tensioned. So, naturally, I can't drill into it to sink some lag bolts or something to secure the power rack.

    I am looking for ideas. Right now I am thinking that a good 500 lbs of weights or so on the rack itself should do well to give it enough inertia that I can safely re-rack or drop weight onto the safeties. I am mostly concerned about tipping backwards on a bad/failed squat and knocking the rack over. Though, I'm not convinced this can even be avoided with bolts because the bolt holes I've seen on these racks arent big enough for substantial hardware anyway.

  2. #2
    Join Date
    Jul 2007
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    North Texas
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    Is the soil under your slab unstable? I've never heard a of post-tensioned residential slab.

  3. #3
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    Apr 2022
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    Tallahassee
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    I don't have an impressive squat, but I've been racking and failing reps inside the cage for months. It moves around a little but it's no problem. I bolted it earlier this week and while it's a solid improvement, it might not be necessary for a while if you have a quality rack.

    I'm guessing your situation leaves you with a subpar rack?

  4. #4
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    Oct 2022
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    I had a post-tensioned slab at my previous house. I found out by trial and error that weighing the rack down with plates created a very stable platform. I kept all my weight on the back uprights and any time I re racked a squat on the front uprights I never felt any shifting of the rack.

    Now, if you're squatting a shit ton of weight that might change.

    Alternative option: in my current house I have my rack in the basement. Instead of drilling into the floor I got 4 4'◊8'◊1" thick particle board and layered them to create 2 inches of thickness. Laid 3/4" stall mat on top the particle board, then secured the rack with 3" lag bolts and thick washers. All that wood is quite heavy, so the platform won't move, and the rack won't move being bolted to the wood.

  5. #5
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    Jun 2015
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    Garage of GainzZz
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    Quote Originally Posted by Mark Rippetoe View Post
    Is the soil under your slab unstable? I've never heard a of post-tensioned residential slab.
    Right. Even if itís an architectural thing, Iíve never heard of a residential garage slab having anything more than welded wire fabric in it.

  6. #6
    Join Date
    Feb 2020
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    To be honest, you likely don't need to bolt it down if the rack itself is remotely substantial. Bolting it would be a nice extra but I don't think it's necessary, especially if it means drilling into your garage floor. Another, and to me a more preferable option, is to put the rack on a platform and bolt it to that and not the actual floor.

  7. #7
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    Nov 2022
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    Quote Originally Posted by Mark Rippetoe View Post
    Is the soil under your slab unstable? I've never heard a of post-tensioned residential slab.
    I am out west, it seems to be common with more "modern" residential slab here (made after 2005+).

    Quote Originally Posted by Jewelcity304 View Post
    I had a post-tensioned slab at my previous house. I found out by trial and error that weighing the rack down with plates created a very stable platform. I kept all my weight on the back uprights and any time I re racked a squat on the front uprights I never felt any shifting of the rack.

    Now, if you're squatting a shit ton of weight that might change.

    Alternative option: in my current house I have my rack in the basement. Instead of drilling into the floor I got 4 4'◊8'◊1" thick particle board and layered them to create 2 inches of thickness. Laid 3/4" stall mat on top the particle board, then secured the rack with 3" lag bolts and thick washers. All that wood is quite heavy, so the platform won't move, and the rack won't move being bolted to the wood.
    This seems to be the more practical option I think. I am not squatting bar bender weight (yet). I can pick up a couple reasonably thick sheets cut to the proper dimensions at the local Lowe's which should do the trick. That is a good idea, increase the effective surface area of the rack by having wood under it, and then hiding it all under nice weightlifting mats.

  8. #8
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    Use 3 sheets of 3/4". Maybe 4.

  9. #9
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    Mar 2021
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    Quote Originally Posted by Satch12879 View Post
    Right. Even if itís an architectural thing, Iíve never heard of a residential garage slab having anything more than welded wire fabric in it.
    These days, its quite common in certain areas. Where I'm at, almost every single tract house (large tract developments, bigger home builders, etc) is done this way.
    For about 10-15 years now really (to a lesser degree when it first started).

    And yes, its kind of fucky, because your slab will sorta drop down into the garage area, and then the garage has a bit of slope .... the cables will actually go thru all that area. You can imagine the cables dipping down and what not to stay in the center of the slab. A lot of weird unpredictable forces when the cables are tensioned later.
    The form work gets tricky to pour a monolithic slab with the different floor elevations, and to let the cables go where they need to. Its fucking crazy if you ask me.

    I would be super leery about dropping (or even so called "controlled lowering") of deadlifts with iron plates in the garage or any part of the building.

    I would build one of those platforms with the recessed wells full of discarded carpet, etc. for the plates to bounce on.

  10. #10
    Join Date
    Jul 2019
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    I don't have post-tensioned concrete but I wanted to protect my garage floor nonetheless. I used two sheets of 4'x8' 3/4" OSB laid side by side horizontally. Then an additional two sheets vertically. Then right in the middle of that stack, I used a 4'x8' sheet of maple 3/4" plywood. I then cut 2'x4' sections of maple and ran them along the sides closest to the rack. I bolted 1 inch lag bolts through the hardwoods (and I guess a little bit into the OSB). As my squat approaches 500, that damn thing has shown zero signs of moving AT ALL. Also of note: I'm in the deep south where humidity is brutal. I put a moisture barrier on the concrete beneath the OSB particle board and it has shown zero signs of warping. I do have a two degree slope on the garage floor that I could actually feel with my deadlift. One side of the bar always broke ground before the other. I shimmed it and haven't had a problem since. This was all done during COVID when plywood shot through the roof so the OSB saved me a little money.

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