Anchoring screw into expansion joint

[Ken Griffin, Jr]

I don't know if this is the right forum for this question but here it is.
I have to anchor some bypass door floor brackets in a school gym that has an athletic type carpet. I had custom stainless brackets made but it turns out that one of the screw holes for the bracket is exactly over a 1/2" expansion joint in the concrete slab. With the carpet in place, I couldn't see the expansion joint and forgot that it was there when we constructed it in 1986.

I can't adjust where the bracket goes since the doors have to hang plumb. I could have the metal fabricator add on to the bracket and I thought that was the best option. But school is starting and I need to get these installed. So my question is this. Could I place some epoxy in the joint (squirt it through the screw hole in the carpet and then run the screw through the bracket into the epoxy? Would that hold securely? I might be able to remove a little of the expansion material with a drill bit maybe enough for the epoxy to bond to the two sides of the concrete slab.

Any thoughts on this?

Thanks
Ken

[Steve Schlumpf]

Moved here from another forum. Hope someone can help answer this member's question.

[Tom M King]

You can buy anchoring epoxy in the big box stores in caulking tubes. They come with a mixing nozzle, but buy several extras. If an anchor can be set in concrete on either side of the joint, for whatever you design, I'd use one of these Greenlee anchor expanders. http://www.amazon.com/Greenlee-870-A.../dp/B001SMN7E0 They come in several different sizes. They aren't cheap, but can often be found on ebay for half or less price. The good thing about them is that they allow you to set the expanding lead anchor flush with the inside surface, and don't depend on an exact hole depth to expand the anchor like pound in ones do.

I use them for all sorts of purposes from mounting electrical boxes to concrete or even stone, and flashings mounted to masonry, including chimney roof intersections. I've never had a single one fail in the decades I've been using expanding anchors. The Greenlee expander is worth it even if you have to pay retail. Having to drill a hole exactly the right depth, and get exactly the right length bolt often becomes a PIA. With this tool, you drill the hole plenty deep for the bolts you have, and it doesn't matter. The anchor ends up flush with the face of the wall, and the bolt can screw all the way through it.

I would prefer the mechanical anchor on one side mounted securely in concrete, rather than epoxy in an expansion joint.

I'll check back in case you have any questions about how this works.

[David Hawxhurst]

this is a question best answered by the technical experts at one of the epoxy manufactures.

or simply do what tom has suggested.

[Pat Barry]

What size screws are you using? How deep can you go? I assume you are using expansion anchors and screws, right? which ones?

[Tom M King]

I expect this is for a guide for the doors, so they wouldn't have to be huge, but that's just a guess from what we have to go by. I have those Greenlee anchor expanders from 10-24 up through 3/8.

[Peter Quinn]

They use epoxy to anchor mud sills to foundations as a retro fit in earthquake zones. I'm pretty sure that it will hold the guides on a track door. But if the expansion joint is one of those homesote type spongy things and not just a line scratched in the concrete, you would be securing to almost nothing. If it's one of those metal compression type things, not sure how much purchase you can get there either, but in ever case if you can add enough epoxy to bridge the two sides of the concrete, I can't see that moving.

[Bruce Wrenn]

The expansion joint allows the two pieces of the slab to MOVE. Most likely your anchor would quickly fail. Can you drill another hole in bracket that would allow you to fasten into either of the slabs? SS drills a lot easier than most think, esp when using a cobalt bit, which can be purchased at the BORGS.

[Paul Grant]

It's not an expansion joint, it's a control joint to try and prevent unwanted slab cracks during the concrete cure. Peel back the carpet, Cut out a portion of the slab 12" x the door width and repour, it's not a big deal.

[Bruce Wrenn]

It's not an expansion joint, it's a control joint to try and prevent unwanted slab cracks during the concrete cure. Peel back the carpet, Cut out a portion of the slab 12" x the door width and repour, it's not a big deal.

OP stated that was a 1/2 wide expansion joint. It's a big deal to cut out a slab and repour. He could drive a wedge of treated wood into joint, and fasten bracket into it using SS screws.

[Tom M King]

I've used this stuff for all sorts of purposes it's not intended for, and it holds up well. It's usually located where the bags of concrete are, and not with the other epoxies or caulking tubes.

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