Is it safe to use a wedge expansion bolt in concrete blocks?

Question

I want to hang a Rogue P-4 pull-up bar from a wall. The wall is concrete block with .5" of strapping on it, and 1" drywall over that. The pull-up bar is made with 1" steel tube. Concrete block walls are 1.5" wide on average, so I'm at 4" of depth and then I put on the bolt. So I'm looking at 5" long wedge compression bolts.

The pull-up bar has 1/2" holes in it. However, my sense is that using 1/2" bolts will require perfect alignment. According to websites, 3/8" concrete expansion bolts have pull-out strength of roughly 1000 lbs. Only the top four will have pull-out loads (the arrangement is two holes on the top of each of the two brackets and one hole on the bottom). So that's 4000 pounds. A 300 pound person jumping up and grabbing on the bar may pull 2g, so that's 600 pounds of force, and double it for the 30" cantilever, so 3/8" concrete expansion bolts should be fine.

Here is my concern: On this website for the bolks I'm thinking of using, the website says "Do not use in brick or blocks." So my question is this: are all wedge expansion bolts contraindicated for all concrete blocks, or just the ones that I'm looking at? If they are all contraindicated, then how do I mount the thing?

EDIT: I am in a townhouse and we do not know if there is a single row of blocks between the units or two. We also do not know if they are filled or not. There is good but not perfect sound isolation between the townhouses and this is an adjoining wall. Here is a picture of what it looks like:

Answer 1

If you read the specs for most concrete anchors, the strength depends on the depth of embedment and the strength of the concrete. Many are not rated for overhead use.

When anchoring into the middle of a cell - the hollow part - you have limited thickness of material - the standard thickness being 1-1/4" - so you have limited depth of embedment. That will limit the strength of your attachment.

The anchor specs will give different numbers for different concrete PSI. Not all block is created equal - some are really strong, some are not. Since you seldom know the strength of the block, it's best to err towards the low end. A lot of CMU block used is 2000 psi.

The table below snipped from one manufacturer's specs would show the 3/8" anchors you're considering are specified for 1-1/2" embedment, at 1-1/4" you're a little shy. If you get some blowout / mushrooming when the bit goes through the block - which you can't see, but almost always happens - you'll have less than 1-1/4" embedment.

For your application, keep in mind that if anything goes wrong - you wobble the drill bit and oversize the hole a little, or just hit a sandy spot in the block - the fastener might not be up to spec. If one of your top two anchors is weak, it could be ugly. For this and other reasons you don't want to calculate the load and design something that just covers it, or covers it comfortably, you want to build for at least double the expected load.

All this in mind, hands down I would recommend using 1/2" Snaptoggles or similar product. Traditional spring loaded toggles would probably be fine but this newer style toggle is much easier to work with for this type of application, and stronger. They have a rating for block, and are rated for 2,038 pounds of pullout tension in block with high grade bolts.

These are easy to use and are much more forgiving than wedge anchors etc. if your hole is a little ovaled or oversized. The hole for a 1/2" Snaptoggle is 3/4" giving you a little wiggle room with the placement, so no need to undersize the anchor. You can use them with 6" bolts if you want. If you remove or relocate the equipment some time in the future, you'll not be left with a stud you have to cut off - you can just unscrew your bolts and patch the holes.

Answer 2

Hilti, among others I'm sure, makes special anchors for concrete block that is hollow (CMUs). You drill a hole, insert the anchor which has plastic pieces that snug up to the inside of the block. Don't know their weight rating offhand. I also like the idea of adding framing to the wall.Will get more info and edit.

Like others said, the wedge anchors will only work if you have solid concrete. Moreover, they're really intended for floors while fleece anchors are for walls. The hilti anchor is unique.

Found this good article but it doesn't mention the type that Hilti makes. https://www.concretefasteners.com/diy-articles-anchoring-concrete-fasteners-to-block-wall/

At orange box store I found something like it called a "flip toggle".

Answer 3

Use a sleeve anchor,,drill a pilot hole, then work your way up with larger drills until you reach the proper diameter hole. Put a two part epoxy construction adhesive on the sleeve, install the sleeve then lightly tighten it so as not to break the concrete block, just enough to center it in the hole.

Answer 4

I also didnt find any of the expansion bolt manufactures that could recommend using an expansion bolt in anything but solid concrete stating specifically "Not for use in cement block". They do give rating specifics for such things as 'Maximum Force" before pullout: 2000 lbs for a 1/2" x 4 1/2" zinc plated bolt. I scanned some of the questions and answers on Amazon. Some stated they had attached it to block with stable results. I'd favor the recommendations of the bolt company to not rely on it securing your pull-up bar. If you decide to use the bolts locate them in the mortar joints.

If you attach (2) 2x6 vertically (one for each side) from the floor to higher then the top bracket hole using expansion bolts spaced at 16 inches on center; it should be strong enough to than bolt you brackets to the 2x6 (unless you kipp!).

Other ideas involve drilling 5/8" anchor holes for 1/2" all-thread glued with epoxy glue. Using anchor epoxy would hold.