I apologize for the length of this post, but more than once I've asked for advice on a forum, gotten it, followed it, and then found out it was wrong because I unintentionally left out some important detail.

I'm trying to hang some large shelves on a concrete/cinder block wall, and have a serious problem: several of the anchors have pulled loose, and the rims of the holes are crumbling a bit. I strongly suspect my biggest mistake (of the many I undoubtedly made) was choosing anchors that were too short.

The Project:
Hang two 48x22 shelves on a block wall, strong enough to hold 200-300 lbs each. Sounds simple right? That's what I thought anyway...

The Materials:
3/4" plywood, two 20x13 heavy duty brackets (from Home Depot) per shelf with included hardware, Hilti sleeve anchors, 5/16 x 2 5/8.

The Challenges:
A) I had no idea whether the blocks are cinder or concrete, or filled or hollow.
B) Slightly off center of one of the shelf locations is a 34" wide window, solidly boarded shut but inset by a few inches.
C) The wall is uneven...hanging naked brackets would not only result in a shelf that is not level, it'd be off level by different amounts from end to end.
D) I have limited tools and budget, and this project is the sum total of my experience with masonry projects.

The Plan:
Drill holes to set the brackets 36" apart, using a rotary masonry bit and cordless drill (I don't have a hammer drill, plus I read that hammer drills aren't good for cinder block). Anchor a short 2x4 to the wall for each bracket, using 2 anchors (top one to the right of the bracket, bottom one to the left), plumb them with shims, and then attach the brackets to them using the screws that were supplied with the bracket (#14 x 1.5").

Complications During Execution:
Turns out the blocks are not hollow (thus toggle bolts are not an option). On some of the holes, the drill bit would reach a point where it would cease to go deeper...I'm guessing this is an indication that the blocks are cinder block with concrete (or grout?) fill. I suppose this is where a hammer drill would be handy. Further progress was only possible by allowing the bit to drift, creating a hole that was not perpendicular.

Eventually I managed to get all 4 brackets mounted, and the plywood attached to one pair. Was gone for a week and when I returned, one of the remaining brackets was hanging about an inch fro the wall. With some light tugging the bottom anchor came loose as well. Upon double-checking the other brackets, I discovered one of the bottom anchors for the "finished" shelf had been tightened too far and would pull right out if not for the other anchor.

Plan B:
Upgrade anchors to 3/8 x 3", this time Red Head brand, and switch from sleeve to wedge. My reasoning was that the wedge anchors require more torque, so I figured they'd be more difficult to over-tighten, thicker anchors would allow me to clean up/straighten the holes, and longer would set more solidly. Result: same problem, except this time the anchors pulled loose even easier (argh!). I'm guessing 3" still wasn't long enough, considering that they have to go thru 2x4's also.

Now what? I was going to ask if I should use injectable adhesive, but apparently that requires a special injector ($129...not in the budget). Because of the window I can't really move the brackets without widening the spacing between them further than they should be. So I need to use the existing holes if possible.

So, finally, here are my questions...

Would my "Plan B" actually work if I use longer anchors? If so, how much longer?

Should I borrow/rent a hammer drill to use? If so, should I first use rotary drill/bit on the cinder block, then switch to hammer drill for the fill?

Is there any way too judge when to stop tightening anchors without a torque wrench?

How do I determine if/how many anchors will handle the load when mfr specs don't say? (neither Hilti nor Red Head seem to make that info available)

And for future reference, is there any way to detect if a painted wall is cinder block or concrete block?

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Any and all responses are greatly appreciated!!

BC

 

why not stand 2 parallel 2x4's on the floor, secure them to wall, & then attach shelf brackets w/wood screws ? find info both sites listed as ' shear strength ',,, iirc, its 10,000# & there's also pullout forces listed,,, i'd use 3/8" bit, bosch bulldog hammer drill, & wedge anchors IF the cells are filled,,, butterfly's if they're not to hold the 2 x 4's straight vertically,,, gravity's your best friend - or, at least, mine

 

I would use PL 8X on the back of the 2x4 and mechanical anchor only on top. Why invite trouble by drilling a hole in the bottom of your boat? the bottom bolt is not holding anything anyway.

 

even better, chan wish i'd run into you last year

 

Thank you stadry and chandler! Excellent idea to run the 2x4's to the floor. It's one of those great "seems-obvious-once-it's-pointed-out" solutions. Maybe one of the reasons it didn't occur to me is because gravity never seemed like much of a friend to me (based on my injuries anyway).

I'm still a bit leery about making sure the anchor at the top stays secure, but based on the fact that wedge anchors are a tried and true method in general, and you recommend them for this project in particular, I'm going to stick to my guess that I simply should have chosen longer ones. Upon thinking about it more after readying your replies, it makes sense. Minimum embed depth for this project would be 1.5", which I thought I had...but most if not all of that depth is apparently cinderblock. I need that much depth into the fill, in addition to the depth needed to get to the fill. And I'm hoping that once I'm embedding into something that's actually stable, the "how much torque" question will answer itself.

As for the PL 8X (I had to look that up btw...cool product!), I love that idea too, and will try it out with next pair of shelves I'm now going to be doing on another wall. Unfortunately, the current wall is so uneven I'd end up with a 2x4 only attached at the top and a bunch of shims glued to the wall. So in this case, it might be more of a "if the boat is already sinking, what's another hole?" Besides, for me trouble doesn't wait for an invitation, it has it's own key.

 

Build or buy shelving units.
Whys it need to be attached to the wall?

 

I recently built 2 walls worth of shelving, 7' tall in my wife's Happy Room (she makes quilts there, and stores hundreds of yards of fabric). All of it rested on the floor, and was anchored to the wall only at the top, every 4' or so.

 

There are several semi-mobile pieces of equipment (on casters) along the wall that occasionally need to be pulled out to be used, or moved to the side to make room for another to be used.


Thanks BridgeMan45, good to know.

Incidentally, the plot thickens (or thins, depending on your point of view)... I've drilled the 4 new holes for the tops of the 2x4's, to a depth of 3.75" to accommodate 5" anchors (after going through a 2x4). Or, that is, I drilled 2 holes to that depth. The other 2 holes punched through to empty space after the first 2". (And no, none of the holes were in the grout.) So, yet another run to the store for toggles. Nothing's ever simple...lol

 

I disagree that "hammer drills aren't good for cinder block". The drill needs to drill as fast as possible to prevent wobble which makes the hole bigger than intended.

 

IMO, "hammer drills" are fine for concrete block. It is SDS drills that can cause problems. Vibrations are further apart and much more pronounced than hammer drills.