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Old 03-25-2013, 4:53 PM
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John Browning John Browning is offline
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Originally Posted by paul0660 View Post
Yeah you could park your pickup on it if it would fit.

My resume is a dozen building projects and getting generals and subs to not rip me off, no matter how smart they act, and 3 lawsuits that I won.

I mentioned epoxy because half the time noobs will rip the red head hole up by over tightening.

I offered an alternative because I know how post tensioned slabs are constructed. They aren't hand grenades, and the tendons are not within two inches of the surface, which is why I noted that dimension.

So, in other words, your only contribution here is to offer nothing. The only thing you did mention, to look for a stamp, is also wrong. My home is not marked anywhere, and many homes with PT slabs are not marked. We'll get to that later.

A 2in hole in a PT slab voids a home warranty for most people. That is very bad. Generally those tendons are 2in from the surface, but they don't always run parallel to the surface so you can absolutely hit one at less than 2in. That alone would be a reason to never drill a PT slab. Even if you were to drill a 2in hole and miss a tendon, a 2in epoxy anchor offers virtually no strength. A 2in hole with epoxy offers less than 1/8th the strength of a 6in hole, and the force requred to pull the anchors is less than the weight of a decent mid-level safe.

A real contractor will get an x-ray or use GPR before they ever drill a PT slab. If you want to go ghetto, mess up your life DIY like you're suggesting, here is some factual info to digest.

LET ME BE CLEAR, AS A LICENSED CONTRACTOR, ONLY A TOTAL MORON DRILLS THEIR OWN PT SLAB. NEVER EVER DRILL A PT SLAB. I CANNOT STRESS THIS ENOUGH. If you're still wanting to drill a PT slab, this is what a very stupid hypothetical contractor would do. I am not advising anyone to do this, because it is very stupid. Despite any reasonable professional advice to avoid it, he would look at the outside of your slab. There will be grouted holes 3 to 4 inches in diameter every 3 feet or so. The best way to tell if you have a PT slab is to look for these holes, and look at a side where there is no concrete poured next to the foundation. Do not rely on the slab being stamped as PT. He would guess where the cables run and drill, which is stupid. PT cables will be covered typically in a red plastic, so if he drilled it and hit plastic, he would stop what he is doing and then drive away, leaving you with a big problem. He probably had no idea that is the case, though, so when he hits the plastic, he keeps going until he snaps the cable. Then he realizes something is wrong, packs up his tools, and drives away hoping you don't have his information to track him down. That is why you don't do this yourself or hire very stupid contractors.

The tendon anchors are under 10,000-30,000 pounds of stress in most residential slabs. If you hit a tendon, they fly apart like something under 30,000 pounds of stress, which is violentlly. The anchors can (and do) fly a few hundred feet and people have been killed by drilling PT slabs. Smart people don't drill them ever on their own, and professional contractors will not drill them without x-ray or GPR.

If you don't mind ruining your foundation and killing yourself or someone else in pursuit of a 2in hole that offers no support, take paul0660's advice. Make it clear to your attorney that it was paul0660 offering that advice, and that I advised against it when you want to file your lawsuit. If you want to have a safe bolted to a PT slab, do what I said above which is to create your own housekeeping slab that you can drill and not worry about. Do not drill a PT slab. You can listen to a licensed contractor talking the talk and then walking it, or some internet certified keyboard expert. It is your house.

Here is a nice video showing what happens when just one PT cable fails.

Securing a safe to a Post-tension slab - DIY

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Originally Posted by KWalkerM View Post
eh why bring logic into this, that makes too much sense... besides when you have bested a fool, you have accomplished nothing and he is a fool.

Last edited by John Browning; 03-25-2013 at 5:24 PM..
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