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I have a predicament, I am putting up a shelf into the wall.

The wall is plaster, and then hollow and then concrete. I have screws with toggle bolts on them.

The 2 inch screw with the toggle bolt was too short to get the toggle bolt inside the plaster to the hollow part.

The 3 inch screw with the toggle bolt is too long because it hits the concrete. But the toggle bolt will reach into the hollow part.

How do I approach this dilemma? Do I need to drill into the concrete somehow? I think my current drillbit is incorrect for doing this, but I'm not sure.

Insight appreciated

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Are the toggle wings too long to open up inside the gap in the wall? Stick a small object through until you hit the concrete, and mark off the distance. If your measured distance minus the plaster thickness isn't longer than the toggle wings, then you need a different bolt or you need to drill out the concrete. Otherwise, you can do as dbracey suggests and cut the 3" bolt down to between 2 and 3". – Doresoom Mar 8 '12 at 19:13
what tool would I use to cut the metal bolt? also, even with the 3" bolt I had to wiggle the toggle bolt in one side at a time, because the concrete was too close. I'll measure – cqm Mar 8 '12 at 19:15
If you have a dremel with a cutoff wheel attachment, that would work. Otherwise a vise and a hacksaw could do it. – Doresoom Mar 8 '12 at 20:37
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Find a stud, problem solved. – Tester101♦ Mar 11 '12 at 13:49
@Tester101 That solution is way too simple. We need to add at least 5 steps, one of which requires kayaking to Alaska. :) – Doresoom Mar 12 '12 at 15:31

1 Answer

up vote 3 down vote

Are you comfortable with cutting the bolt to a length between 2" and 3"? That would be simplest.

Another possibility would be to use another piece of wood between your shelf and the wall to create more thickness for the 3" bolts.

If the concrete is actually concrete block, you can drill into that quite easily with a masonry bit from your local hardware store. If it is an actual poured concrete wall, best not to bother.

ADDED:

To shorten the bolts:

A) Take the bolt to a hardware store, tell someone you want the same bolt but in a 2.5" length - this is likely the easiest thing.

B) Cut the bolts:

  1. Thread a nut onto the bolt and spin it back towards the head.
  2. Use a hacksaw to cut the bolt (if you clamp it, clamp on the nut and head - not the threads) - OR - use a Dremel with a cut-off wheel - OR - use boltcutters!
  3. Unscrew the nut from the bolt; this will clean up the damaged threads where you cut it.
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how can I tell what material it is? I can only shine a flashlight through the hole and see there is something hard there that is not wood. The outside of the building is bricks with concrete in between the bricks – cqm Mar 8 '12 at 19:12
If there is a big hollow space I don't think you want to screw into the concrete - there will be a lot of shear force on the screw and it might not hold it since it's not designed for a large gap between load and the surface its being anchored to. Cut the screw to the desired length instead and stick with the toggle. – Steven Mar 8 '12 at 19:18
what tool would I use to cut the screw – cqm Mar 8 '12 at 19:26
I think he's proposing just making some room for the ends of the bolts, and still using the toggle - not screwing into the concrete. – dbracey Mar 8 '12 at 19:26
See added lines in the answer above. – dbracey Mar 8 '12 at 19:27
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