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Discussion Starter · #1 ·
I would like to anchor a floating shelf to a concrete block (CMU) wall. The shelf will be constructed with a 2x4 ledger that has several "arms" extending out about 10-12 inches from it, screwed in from the back. A hollow shelf "sleeve" will slide over the arms after mounting the ledger/arms to the wall. I built one in my last house but it was mounted to a stud wall with lags which was quite easy.

I want to create the same type of shelf in my new home which has a concrete block (hollow CMU) wall that I will mount the shelf to. That wall is covered in sheetrock with 1x2 furring strips attached to the wall first. I am wondering what the best type of fastener would be to attach the ledger to the concrete block wall. The shelf would need to hold the weight of the shelf itself plus contents for a total of about 50 lbs. The shelf will be about 12 inches deep. There will be no supporting angle brackets -- the shelf will be "floating" with no visible supports.

I have researched "sleeve" anchors that say they can be used in solid or hollow block, but I can't find any info on how they work (or if they work) if installed in the hollow part of the block. I've also seen mesh sleeve/epoxy anchors, but they are not easy to come by locally and I'd prefer something that could be removed rather than epoxying threaded rod into the wall. I've used Cobra TripleGrip plastic anchors in the past to hold a TV mount to a concrete block wall for years without any problems, but I'm not sure if that would work here. I would say the weight of the TV and bracket is greater than the weight of the shelf and contents, but I'm not sure about the difference in tension vs shear in each case. Tensile/pull-out strength would be most important here since there are no supporting angle brackets below the shelf.

Is there a type of screw-in fastener that is best-suited for this type of application? One that will work whether I happen to drill into the hollow or solid part of the block?

Thanks in advance!
 

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Discussion Starter · #3 ·
Thanks! I've used Zip Toggles before with good results, so I may purchase some of those to have on hand for the hollow parts of the block. My only worry about wedge anchors would be that I wouldn't know how close to the edge of the web/block I was and could blow it out during expansion. Of course, even if that happened, I'd still be able to drill a new hole a few inches away and just add a new fastener since I won't be constrained to any specific holes on the ledger.
 

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You say that you want a removable attachment.

Be warned once removed there is nothing short of EPOXY to reattach in the same holes in those C M U.

I myself would just affix a ledger 2X to the C M U with PL construction adhesive.

Then I could build and attach my Floating Shelf to that.

The 2X will be a permanent part of the wall, and will need a large prybar to remove it.

There is Tapcon screws, but they are a one and done deal, if it don't work the first time, they won't work, and the hollow areas don't like to be drilled or screw holes either.

ED
 

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You say that you want a removable attachment.

Be warned once removed there is nothing short of EPOXY to reattach in the same holes in those C M U.

I myself would just affix a ledger 2X to the C M U with PL construction adhesive.

Then I could build and attach my Floating Shelf to that.

The 2X will be a permanent part of the wall, and will need a large prybar to remove it.

There is Tapcon screws, but they are a one and done deal, if it don't work the first time, they won't work, and the hollow areas don't like to be drilled or screw holes either.

ED
Why not a lag shield anchor or sleeve anchor?
 

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I will go with Tapcon in this case. Not the regular Tapcon screws but their hanger screws that accepts threaded bolts.



Tapcon screws are rated for a 500 pound pullout force with a 1" minimum embedment if done correctly.

We routinely use Tapcons to install hurricane tracks on top and bottom of windows, on exterior concrete block walls. Code calls for a 1/4" Tapcon every six inches. You put up heavy steel or aluminum shutters all along the track when a storm approach and it's supposed to withstand a flying coconut thrown at your window by a 185mph gust. Your 50 pound TV should be fine.

We use these hanger bolts when the hardware needs to be removable. Such as a track above and below a door, when the track is left in place it can be a tripping hazard. The regular Tapcon screws are not removable, if you remove it then you have to drill a new hole next time, unless you upsize the screw from 1/4 to 5/16.
 

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I would like to anchor a floating shelf to a concrete block (CMU) wall. The shelf will be constructed with a 2x4 ledger that has several "arms" extending out about 10-12 inches from it, screwed in from the back. A hollow shelf "sleeve" will slide over the arms after mounting the ledger/arms to the wall. I built one in my last house but it was mounted to a stud wall with lags which was quite easy.

I want to create the same type of shelf in my new home which has a concrete block (hollow CMU) wall that I will mount the shelf to. That wall is covered in sheetrock with 1x2 furring strips attached to the wall first. I am wondering what the best type of fastener would be to attach the ledger to the concrete block wall. The shelf would need to hold the weight of the shelf itself plus contents for a total of about 50 lbs. The shelf will be about 12 inches deep. There will be no supporting angle brackets -- the shelf will be "floating" with no visible supports.

I have researched "sleeve" anchors that say they can be used in solid or hollow block, but I can't find any info on how they work (or if they work) if installed in the hollow part of the block. I've also seen mesh sleeve/epoxy anchors, but they are not easy to come by locally and I'd prefer something that could be removed rather than epoxying threaded rod into the wall. I've used Cobra TripleGrip plastic anchors in the past to hold a TV mount to a concrete block wall for years without any problems, but I'm not sure if that would work here. I would say the weight of the TV and bracket is greater than the weight of the shelf and contents, but I'm not sure about the difference in tension vs shear in each case. Tensile/pull-out strength would be most important here since there are no supporting angle brackets below the shelf.

Is there a type of screw-in fastener that is best-suited for this type of application? One that will work whether I happen to drill into the hollow or solid part of the block?

Thanks in advance!
When I attach large mini-split outdoor units to cinder block walls, I use a threaded rod right through the wall with a large washer inside. All the anchors can fail, even the double expansion anchors which are usually the best. The toggle anchors are ok for a pedestal sink where there is no great force and leverage like there would be on a shelf.

Sincerely,

William McCormick
 

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I have used one that is a bolt with an imbalanced bar about 3 times as long as the diameter of the bolt on the inside end. Just line up the bar and slide it in, when it gets to the hollow the bar pivots downward at the heavy end and forms a T. Then slip on a washer and nut and tighten. Usually at hardware stores, or lumber yards.
 

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I have used one that is a bolt with an imbalanced bar about 3 times as long as the diameter of the bolt on the inside end. Just line up the bar and slide it in, when it gets to the hollow the bar pivots downward at the heavy end and forms a T. Then slip on a washer and nut and tighten. Usually at hardware stores, or lumber yards.
The only problem with a toggle or the bar type is that their own ratings are low and any shelf or roll-up gate that you try to mount with anchors is a hazard. A friend wanted to close his store but his roll-up gate was stuck. I went over and one of the slats was stuck he was in a hurry and said just cut that one slat out, all I had was a saws-all to cut it, I didn't have an angle grinder and I said the vibration could take the unit off the wall. He didn't believe me and asked me to do it anyway. I positioned my ladder off to the side of the gate he thought I was a sissy, In under twenty seconds the entire rollup gate came down. Some guys still anchor them I always through bolt with a threaded rod.

Cement or cinder blocks have great compression strength but zero cohesive strength in engineering. That is why when you drill through a cinder block wall with a hammer drill you get that big funnel that pops out on the other side the cement has no cohesive strength. Electricians have taken huge lengths of pipe racks supported by cement anchors using a saws-all on a pipe in the rack.

Sincerely,

William McCormick
 

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If the toggles vibrated loose they were improperly installed.
 

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The only problem with a toggle or the bar type is that their own ratings are low and any shelf or roll-up gate that you try to mount with anchors is a hazard. A friend wanted to close his store but his roll-up gate was stuck. I went over and one of the slats was stuck he was in a hurry and said just cut that one slat out, all I had was a saws-all to cut it, I didn't have an angle grinder and I said the vibration could take the unit off the wall. He didn't believe me and asked me to do it anyway. I positioned my ladder off to the side of the gate he thought I was a sissy, In under twenty seconds the entire rollup gate came down. Some guys still anchor them I always through bolt with a threaded rod.

Cement or cinder blocks have great compression strength but zero cohesive strength in engineering. That is why when you drill through a cinder block wall with a hammer drill you get that big funnel that pops out on the other side the cement has no cohesive strength. Electricians have taken huge lengths of pipe racks supported by cement anchors using a saws-all on a pipe in the rack.

Sincerely,

William McCormick
Thanks, good to know. every one I ever used it for was mostly in shear and i always used a small rotary hammer that seemed to go through smoothly, it wasn't hammering very hard.
 

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If the toggles vibrated loose they were improperly installed.
Look at the actual rating on the package it is low, especially if you are talking about the leverage of a shelf. They are great for shear and to hold something like a porcelain pedestal sink to the wall where the only force that is exerted against them is a rare force of someone grabbing the sink perhaps when they slip coming out of the shower. The pedestal supports the sink vertically so all they do is hold the sink to the wall, after you apply the caulking they are just backup.

But if you put some weight on a shelf supported by them they bend, because the rating is actually rather low on some brands others rate them up to 750 pounds which is not true for anything but a perfectly placed static load. That thin threaded nut and the sheet metal wings just collapse under any kind of load resembling 750 pounds with any kind of jostling. When you load it to about 300 pounds and jostle it, it starts to loosen. It may not give but it will not stay tight. A couple times having no other way to mount things to a wall, we used them, and as they were being tightened to pull the wall that had a slightly bowed 2"x4", to the object being tightened to the wall they gave way. That same task could have been done with a 2 1/2" drywall screw and completed. I have used them to hang TV's they are ok in sheetrock, but we usually can catch at least one beam to really make sure it stays on the wall.
The way to see them fail is to load your shelf with the load you plan to store and then drop a full paint can on the shelf perhaps from a foot above the shelf, the toggles just give some. You might be able to tighten them back up but they are not what I would want my kids standing under when they are full of heavy stuff like paint cans.

Sincerely,

William McCormick
 

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Look at the actual rating on the package it is low, especially if you are talking about the leverage of a shelf. They are great for shear and to hold something like a porcelain pedestal sink to the wall where the only force that is exerted against them is a rare force of someone grabbing the sink perhaps when they slip coming out of the shower. The pedestal supports the sink vertically so all they do is hold the sink to the wall, after you apply the caulking they are just backup.

But if you put some weight on a shelf supported by them they bend, because the rating is actually rather low on some brands others rate them up to 750 pounds which is not true for anything but a perfectly placed static load. That thin threaded nut and the sheet metal wings just collapse under any kind of load resembling 750 pounds with any kind of jostling. When you load it to about 300 pounds and jostle it, it starts to loosen. It may not give but it will not stay tight. A couple times having no other way to mount things to a wall, we used them, and as they were being tightened to pull the wall that had a slightly bowed 2"x4", to the object being tightened to the wall they gave way. That same task could have been done with a 2 1/2" drywall screw and completed. I have used them to hang TV's they are ok in sheetrock, but we usually can catch at least one beam to really make sure it stays on the wall.
The way to see them fail is to load your shelf with the load you plan to store and then drop a full paint can on the shelf perhaps from a foot above the shelf, the toggles just give some. You might be able to tighten them back up but they are not what I would want my kids standing under when they are full of heavy stuff like paint cans.

Sincerely,

William McCormick
Thinking about it I'll bet that little pin is the weakest link. any play in that and everything else starts moving. I'm just an old hippy guess I'll go back to lead shield and lags. wonder if you can still get the square headed ones? I have snapped many heads right at the top of the threads of drywall screws too.
 

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I will go with Tapcon in this case. Not the regular Tapcon screws but their hanger screws that accepts threaded bolts.
I've used Tapcon screws a lot in concrete blocks or brick. They are very straightforward to install (which is why I like them) EXCEPT that for some reason, one in every few screws refuses to tighten. I'm not sure what I'm doing wrong. I use the right size drill bit supplied by Tapcon with a hammer drill. Any ideas?
 

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I've used Tapcon screws a lot in concrete blocks or brick. They are very straightforward to install (which is why I like them) EXCEPT that for some reason, one in every few screws refuses to tighten. I'm not sure what I'm doing wrong. I use the right size drill bit supplied by Tapcon with a hammer drill. Any ideas?
For brick, unless they're concrete, don't use the hammer function, not needed. When hammer drilling concrete do it carefully so the hole doesn't wallow and oversize. If it Tapcon spins, remove it and add a piece of string trimmer line or copper wire when screwing it back in, that usually gets it to tighten.
 
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