Can safe be bolted to post-tensioned slab?

[lawaia]

Has anyone here bolted a safe to a post-tensioned slab? Good idea or bad? I've heard second-hand stories of exploding foundations and other nasty things happening. Can anyone enlighten me with a first-hand experience?

[freonr22]

i know in one of the buildings i worked in, we had a firm come out and x-ray before we core drilled as to not hit any of the cables. i dont know if that was pre or post tensioned... also, im not sure how they would xray a slab, since i think they need access to both sides i thought

[Fjold]

If you use a Hilti gun to fasten it down it shouldn't be a problem. The problem is that about halfway through your slab there are cables strung under tension. If you hit one of those with a drill bit big enough to to set an anchor you could pop that cable and crack your slab.

I have the same thing in my house and unfortunately in finishing the foundation they covered over the ends of the cable tension locks so you can't even measure where they are to mark the cable locations.

[jasilva]

You do not want to hit the cable, if you manage to break the cable it will most likely blow a pretty good size hole in your slab. Odds are the cable won't hit you but it will screw your foundation up pretty badly and really damage it's structural integrity.

[lasereye]

Just use drop-in anchors. Drilled properly to a flush finish you won't come any where near the cables.

[chiz]

I was a general foreman doing reinforcing and post-tensioning for 9 years before I before I was disabled and I had broken a few cables while stressing them. Your slab will not blow apart but it will weaken it. Around the perimeter of the house the cables are in the middle of the slab. In the center of the slab the cables are closer to the bottom and you are less likely to hit a cable there. the corner of the house would be a good place because there are no cables along the edge.

[Fjold]

My cables crisscross about every foot through my entire slab.

[SJgunguy24]

Just use drop-in anchors. Drilled properly to a flush finish you won't come any where near the cables.

+1
The drop-in anchors are the way to go. Generally the hole only need to be 5/8"-3/4" deep to get the anchors down enough. The hole will be bigger than the bolt you use.If you go with 3/8" hardware then the hole for the drop in will be 1/2". Keep that in mind before buying hardware. The holes aren't deep but drilling through concrete SUCKS without a Roto-Hammer.

I know some dewalts have a hammerdrill feature but if you try to punch 1/2" holes with that drill.........it won't last very long.

[paintballergb]

I sure wouldn't unless you knew for 100% sure that you weren't going to hit a cable.

[Turbinator]

Ok, so assuming that you don't want to drill into the slab, what other techniques could be used to secure a safe on one of these?

Turby

[colossians323]

Drop in anchors are not the way to go.

Pay the $125 to have them radar your slab, and you can use the studs.

Good luck

[Curtis]

Yes, you can drill into a PT slab. However, you want to make sure you know where the cables are located. I design PT slabs and repairs. It is rare for a tendon to break out of the slab on a residential house. It will shoot out the plugs around the slab edge. If it hit someone it could break a leg.

Although you might be able to locate the tendon location looking at the slab edge, the problem is that the tendons are not run in straight lines. As for shallow anchor bolts, some cities don't even allow for shot pins to be used because they may hit the tendons.

I would try to locate a PT repair crew. They can come out and use equipment to locate the tendons. Work is light, so you should be able to find someone for cheap.

You can e-mail me and I can try to put you in touch with a crew that can locate your tendons.

Curtis
curtis@sterlingse.com

[jamespres2001]

If you are drilling in the garage the cables might not be in the slab. Concrete guy could tell you. If you drill into the slab you will void your warranty on your house and just about anything that goes wrong after that will be outside the warranty. I don't care if the tile in the 2nd floor bathroom cracks, if you drilled into the slab you lose. Warranty can be 10 Years. You should see a marker in the garage that says something like "Warning drilling into this tensioned slab will void your warranty. It doesn't say "if your careful"
I'm not an expert, but in the Const. Field.
Just secure it to the walls and get an alarm.
What I would do is: Set down some ext. plywood, than set some 1/4" steel plate over the wood bent up and tie the steel into the concrete curb or wood rim joist. use expanding anchors drill through the steel into the ply and tighten down. May work.

[Casual_Shooter]

On another forum, someone asked a similar question. The resident safe expert told him that there are epoxies you can use to glue your safe down that are very secure.

[tgriffin]

On another forum, someone asked a similar question. The resident safe expert told him that there are epoxies you can use to glue your safe down that are very secure.

God help you if you need to move your safe though LOL.