Concrete guys, need some help

[RobG]

Problem: Bought a new safe and need to bolt it down but I have a post tension slab. I was able to find the ends of the cables in the slab but, they run different depths and criss cross the slab. What I am considering is building/pouring a small foundation slightly larger than the safe in my garage to bolt it to. Is this slab going to "stick" to the garage floor or will it simply dry and be moveable? And if it is moveable, how can I attach it permanently? Any other ideas are certainly welcomed. Gotta figure it out before its delivered on the 28th.

Thanks

 

[chain]

Re: Concrete guys, need some help

Some plumbing contractors can locate the cable for you and tell you it's depth also. You can pour and attach or make a new slab detachable so to speak. Pour it on plastic it will move, put done a bonding agent (ACRY 60) check my spelling, it will stick. I think I would pour a slab on plastic or have the cables located. PM me if you have anymore questions.

 

[BALLISTIC]

Re: Concrete guys, need some help

I have seen concrete with chalk lines marked on it which indicated where rebar/tension cables were, so we could core a few holes. I am not sure how they knew, but you could probably have this done.

 

[-Nick-]

Re: Concrete guys, need some help

It will be a cold joint and can be separated. Use a 1/8" concrete drill bit for pilot holes 2" deep and look for metal shards in the dust. If you happen to hit one then go to another point 1" to the side of it. Once you have your holes set then widen the holes to 1/2" or whatever you're using for bolts. When you set the bolts use concrete glue as well with any anchor.

 

[Tripwire]

Re: Concrete guys, need some help

A metal detector....mebbe?

 

[The Mechanic]

Re: Concrete guys, need some help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Broker</div><div class="ubbcode-body">It will be a cold joint and can be separated. Use a 1/8" concrete drill bit for pilot holes 2" deep and look for metal shards in the dust. If you happen to hit one then go to another point 1" to the side of it. Once you have your holes set then widen the holes to 1/2" or whatever you're using for bolts. When you set the bolts use concrete glue as well with any anchor.</div></div>
Best answer ^^^^

 

[0481]

Re: Concrete guys, need some help

Call American leak detection. They can find the post tension cables with a small cray machine.

 

[Queequeg]

Re: Concrete guys, need some help

Post tension slabs typically require X-ray survey prior to coring or through drilling . Most Post tension slabs will have the cables set deep enough to allow drilling for things such as floor stops, or fasteners such as tap cons or sleeve anchors for attaching things such as file tracks, data racks, thresholds, etc.

If you were to lay out the foot print of your safe in the desired location, build your form, drill some 3/16" holes about 2" deep for a the strategic placement of several tap cons, vacuum the dust and then apply bonding agent (Follow directions) prior to pouring your concrete, you'll find the pedestal you make to be profoundly immovable. Scarifying the surface of the slab under that foot print, in addition to the other steps will make it even stronger!

As a bonus, it you lay the bolt pattern out for your safe on a template you can set sleeve anchors into the base slab (or lintel bolts) into the pad form prior to pouring your mix.

Post tension cables are not something you want to cut but small diameter drill bits, even up to 1/2", don't need to go more than 2" deep to anchor most fixtures and are unlikely to hit, let alone damage, the cables in most PT slabs.

 

[Maggot]

Re: Concrete guys, need some help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: queequeg</div><div class="ubbcode-body">Post tension slabs typically require X-ray survey prior to coring or through drilling . Most Post tension slabs will have the cables set deep enough to allow drilling for things such as floor stops, or fasteners such as tap cons or sleeve anchors for attaching things such as file tracks, data racks, thresholds, etc.

If you were to lay out the foot print of your safe in the desired location, build your form, drill some 3/16" holes about 2" deep for a the strategic placement of several tap cons, vacuum the dust and then apply bonding agent (Follow directions) prior to pouring your concrete, you'll find the pedestal you make to be profoundly immovable. Scarifying the surface of the slab under that foot print, in addition to the other steps will make it even stronger!

As a bonus, it you lay the bolt pattern out for your safe on a template you can set sleeve anchors into the base slab (or lintel bolts) into the pad form prior to pouring your mix.

Post tension cables are not something you want to cut but small diameter drill bits, even up to 1/2", don't need to go more than 2" deep to anchor most fixtures and are unlikely to hit, let alone damage, the cables in most PT slabs. </div></div>

Qood work Q. I will confirm the part about scarifying/roughing up the concrete
before pouring the new. With the bolts he recommended, you should have no problem. One further thought....start wetting (with water) the area of the pour a day or so before pouring. Keep it wet as that will greatly improve adhesion.

 

[-Nick-]

Re: Concrete guys, need some help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: maggot</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: queequeg</div><div class="ubbcode-body">Post tension slabs typically require X-ray survey prior to coring or through drilling . Most Post tension slabs will have the cables set deep enough to allow drilling for things such as floor stops, or fasteners such as tap cons or sleeve anchors for attaching things such as file tracks, data racks, thresholds, etc.

If you were to lay out the foot print of your safe in the desired location, build your form, drill some 3/16" holes about 2" deep for a the strategic placement of several tap cons, vacuum the dust and then apply bonding agent (Follow directions) prior to pouring your concrete, you'll find the pedestal you make to be profoundly immovable. Scarifying the surface of the slab under that foot print, in addition to the other steps will make it even stronger!

As a bonus, it you lay the bolt pattern out for your safe on a template you can set sleeve anchors into the base slab (or lintel bolts) into the pad form prior to pouring your mix.

Post tension cables are not something you want to cut but small diameter drill bits, even up to 1/2", don't need to go more than 2" deep to anchor most fixtures and are unlikely to hit, let alone damage, the cables in most PT slabs. </div></div>

Qood work Q. I will confirm the part about scarifying/roughing up the concrete
before pouring the new. With the bolts he recommended, you should have no problem. One further thought....start wetting (with water) the area of the pour a day or so before pouring. Keep it wet as that will greatly improve adhesion. </div></div>

You only need to rough it up if you're pouring an additional slab on top. If he does the process we've both quasi outlined then he should be able to bolt the safe directly to the floor slab itself. There's no reason to create more work or add to a platform that would work just as sell if not better. But agreed... sort of...

 

[jr81452]

Re: Concrete guys, need some help

I need a few more details. Do to your reference to a garage, I assume we are dealing with a post tension slab on grade? Or is it an elevated structure? What is the thickness of the slab? What diameter are the tension cables? What is the structure's approximate age? Do you have access to the construction drawings or the name of the engineer who drew them? Is the garage slab at the same elevation as the living level?

With the information provided I would caution against drilling even 2" deep. I've seen post tension slabs as thin as 4". The cables need a full inch of concrete on all sides minimum. So with a 4" slab and 1/2" cables, anything deeper than 1" risks breaking the cable sheath causing problems. Post tension slabs are precisely engineered elements, if you can get a copy of the construction drawings you will be able to locate the cables' exact positions and work around them. I look forward to additional information.

 

[RobG]

Re: Concrete guys, need some help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jr81452</div><div class="ubbcode-body">I need a few more details. Do to your reference to a garage, I assume we are dealing with a post tension slab on grade? Or is it an elevated structure? What is the thickness of the slab? What diameter are the tension cables? What is the structure's approximate age? Do you have access to the construction drawings or the name of the engineer who drew them? Is the garage slab at the same elevation as the living level?

With the information provided I would caution against drilling even 2" deep. I've seen post tension slabs as thin as 4". The cables need a full inch of concrete on all sides minimum. So with a 4" slab and 1/2" cables, anything deeper than 1" risks breaking the cable sheath causing problems. Post tension slabs are precisely engineered elements, if you can get a copy of the construction drawings you will be able to locate the cables' exact positions and work around them. I look forward to additional information. </div></div>

I have no builders info at all. The slab is sitting on dirt or whatever, not elevated. Its 6 years old. What I do see is ~1/4" diameter "ends" of steel sticking out of the foundation. These are approx. 3-4 inches deep, approx. 18-22 inches apart, not completely consistent. The garage is lower than the main living area and graded from the house to the driveway. Where the safe would go inside would put two of the holes approx in between (approx 8 inches or so away) these steel "ends." The other holes would be within a few inches of them.

 

[RollingThunder51]

Re: Concrete guys, need some help

You have gotten some great advice. I'm going to send you in a different direction altogether, leave the original pour alone altogether. The truth is that the vast majority will be stopped cold if you pour a secondary base and bolt to that. For those guys, if they can't tip it over and if you bought a good quality safe, they are done. What weight?

For the pro? They are not there to drag it away. They want to either go in through the lock, or by pattern. They are, for the most part, in. Security system, security system.

The added height of the new pour slab will keep your safe free(er) from flooding of the original floor. Give you better height access, allow you to stop tipping altogether, be moveable later if required. You can also make your form to allow the safe to sit "in" the new base, a real advantage.

Electric lock? Hope not.

 

[RobG]

Re: Concrete guys, need some help

Thanks guys. I think I am going to go with the small slab route. That way there is no going through my office carpeting, worrying about the cables, it will set it up higher, and it will actually be in a more secure location. There is a small ledge that the foundation sits on since the garage floor is lower that I can drill into and place rebar that will connect the two together. 750 lbs empty and a slab of 44"x27"x5" should keep it down to the ground.

 

[jr81452]

Re: Concrete guys, need some help

Sounds like a good choice. Remember to dill your #5 rebar 6" into the existing and use 3000psi grout to anchor it, with min. 8" lap into the new, if you go that way. If your safe is between 48" and 80" tall, a 6" wide conc. flange front and back should prevent tipping (10" in the front if your door is over 300lb or 30" wide). Set your anchor bolts 1.5" above the new slab's base and use fibermesh in the conc. mix.

Take pics

 

[bgbill]

Re: Concrete guys, need some help

Just use Titan Bolt's (it is like a big tapcon), if you hit a cable with a masonry bit you will know it, it will be very difficult to weaken the post tensioned cable with a masonry bit, even if you stayed on it for awhile.

 

[bgbill]

Re: Concrete guys, need some help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jr81452</div><div class="ubbcode-body">Sounds like a good choice. Remember to dill your #5 rebar 6" into the existing and use 3000psi grout to anchor it, with min. 8" lap into the new, if you go that way. If your safe is between 48" and 80" tall, a 6" wide conc. flange front and back should prevent tipping (10" in the front if your door is over 300lb or 30" wide). Set your anchor bolts 1.5" above the new slab's base and use fibermesh in the conc. mix.

Take pics

</div></div>

He is worried about hitting a post tensioned cable, so installing rebar into the existing slab isn't going to help him avoid that.

BTW Grout is not the proper way to attach rebar to an existing slab, it will not have any structural integrity, epoxy is the correct way to do this.

Most safe companies I know of use titan bolts (Basically a big Tapcon), they hold better than a wedge anchor (Redhead) and can easily be removed if and when you decide to move the safe.

 

[RobG]

Re: Concrete guys, need some help

I went with the slab. I used rebar epoxied into the back edge (no cables in this section) and some rebar epoxied 1.25" into the floor. Plus 5 bags of Quikcrete and it seems solid. It aint pretty by any stretch but, it should do the trick.

 

[jr81452]

Re: Concrete guys, need some help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bgbill</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jr81452</div><div class="ubbcode-body">Sounds like a good choice. Remember to drill your #5 rebar 6" into the existing and use 3000psi grout to anchor it, with min. 8" lap into the new, if you go that way. If your safe is between 48" and 80" tall, a 6" wide conc. flange front and back should prevent tipping (10" in the front if your door is over 300lb or 30" wide). Set your anchor bolts 1.5" above the new slab's base and use fibermesh in the conc. mix.

Take pics

</div></div>

He is worried about hitting a post tensioned cable, so installing rebar into the existing slab isn't going to help him avoid that.

BTW Grout is not the proper way to attach rebar to an existing slab, it will not have any structural integrity, epoxy is the correct way to do this.

Most safe companies I know of use titan bolts (Basically a big Tapcon), they hold better than a wedge anchor (Redhead) and can easily be removed if and when you decide to move the safe. </div></div>

As you can see from his response, HE understood that the rebar went horizontally into the existing slab. Therefor he would know the location of the tensioned cables and be able to avoid them.

I don't know of anyone who specs 3000psi grout that isn't an <span style="font-weight: bold">epoxy anchoring grout</span>. Unless perhaps they're in the Well filling industry.

 

[bgbill]

Re: Concrete guys, need some help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jr81452</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bgbill</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jr81452</div><div class="ubbcode-body">Sounds like a good choice. Remember to drill your #5 rebar 6" into the existing and use 3000psi grout to anchor it, with min. 8" lap into the new, if you go that way. If your safe is between 48" and 80" tall, a 6" wide conc. flange front and back should prevent tipping (10" in the front if your door is over 300lb or 30" wide). Set your anchor bolts 1.5" above the new slab's base and use fibermesh in the conc. mix.

Take pics

</div></div>

He is worried about hitting a post tensioned cable, so installing rebar into the existing slab isn't going to help him avoid that.

BTW Grout is not the proper way to attach rebar to an existing slab, it will not have any structural integrity, epoxy is the correct way to do this.

Most safe companies I know of use titan bolts (Basically a big Tapcon), they hold better than a wedge anchor (Redhead) and can easily be removed if and when you decide to move the safe. </div></div>


As you can see from his response, HE understood that the rebar went horizontally into the existing slab. Therefor he would know the location of the tensioned cables and be able to avoid them.

I don't know of anyone who specs 3000psi grout that isn't an <span style="font-weight: bold">epoxy anchoring grout</span>. Unless perhaps they're in the Well filling industry. </div></div>


I have never heard of epoxy anchoring grout, the only epoxy grout I am aware of is used for tile when we are worried about staining.

I have used High Strength Epoxy such as Simpson, for anchoring rebar into slabs and footer's, or attaching FCO signs to masonry walls.

I have used grout under columns and posts.

I don't understand how he is going to attach the rebar to the existing slab without drilling into the existing slab.

There is no need for all of the hassle of pouring a slab on top of his existing slab, he can drill a probing hole with a 5/32" tapcon bit to see if it will clear, if it does, he can go with a larger bit and use a Titan bolt.

 

[Guest]

Re: Concrete guys, need some help

If you ever need to cut the concrete, I know a guy

 

[jr81452]

Re: Concrete guys, need some help

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jr81452</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bgbill</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jr81452</div><div class="ubbcode-body">Sounds like a good choice. Remember to drill your #5 rebar 6" into the existing and use 3000psi grout to anchor it, with min. 8" lap into the new, if you go that way. If your safe is between 48" and 80" tall, a 6" wide conc. flange front and back should prevent tipping (10" in the front if your door is over 300lb or 30" wide). Set your anchor bolts 1.5" above the new slab's base and use fibermesh in the conc. mix.

Take pics

</div></div>

He is worried about hitting a post tensioned cable, so installing rebar into the existing slab isn't going to help him avoid that.

BTW Grout is not the proper way to attach rebar to an existing slab, it will not have any structural integrity, epoxy is the correct way to do this.

Most safe companies I know of use titan bolts (Basically a big Tapcon), they hold better than a wedge anchor (Redhead) and can easily be removed if and when you decide to move the safe. </div></div>


As you can see from his response, HE understood that the rebar went horizontally into the existing slab. Therefor he would know the location of the tensioned cables and be able to avoid them.

I don't know of anyone who specs 3000psi grout that isn't an <span style="font-weight: bold">epoxy anchoring grout</span>. Unless perhaps they're in the Well filling industry. </div></div>


<span style="color: #FF0000">I have never heard of epoxy anchoring grout, the only epoxy grout I am aware of is used for tile when we are worried about staining.</span>

<span style="color: #FF0000">I have used High Strength Epoxy such as Simpson, for anchoring rebar into slabs and footer's, or attaching FCO signs to masonry walls.

I have used grout under columns and posts.</span>

I suspect you are misinterpreting the term Grout. If you use Simpson products, then you have used epoxy anchoring grout.

From the Simpson site: "SET Epoxy-Tie® epoxy is a two-component, 1:1 ratio, high solids, epoxy-based adhesive for use as a high strength, non-shrink <span style="font-weight: bold">anchor grouting material</span>."
"PROPERTY / TEST METHOD / RESULTS
Bond strength / ASTM C 882 / 3,218 psi (2 days)"


You will find a similar description for most such products used for threaded rod or rebar.

<span style="color: #FF0000">I don't understand how he is going to attach the rebar to the existing slab without drilling into the existing slab.</span>

Drilling into his slab wasn't the primary issue. The real problem was in avoiding the hidden post tensioned cables. Since the cable's end locations are clearly visible from the side of the slab, horizontal installation of the rebar allowed him to avoid them.

<span style="color: #FF0000">There is no need for all of the hassle of pouring a slab on top of his existing slab, he can drill a probing hole with a 5/32" tapcon bit to see if it will clear, if it does, he can go with a larger bit and use a Titan bolt.</span>

Most modern masonry bits (including tapcon) use Carbide tips. They can and will cut into steel cables and (just as importantly) the polymer sheaths protecting the cables from long term corrosion. Without knowing the exact location of the cables, drilling into a post tensioned slab is risky at best, disastrous at worst. A secondary slab avoids the risks, if installed correctly.

 

[bgbill]

Re: Concrete guys, need some help

jr,

What is the point of putting rebar in a slab on top of an existing slab?