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Re: Drilling into concrete ceiling

said by Subaru:

Well I now know how thick the ceiling is.. had some work done so I'd say it's about 1/2" or so.

.........so it's cement board on studs? if so, get the stud centers and mount two 2x4's spanning at least two studs, spaced so the projector will fit over them, and fasten your projector to the 2x4's.

robbin
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Leander, TX

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It's plaster. No tapcons. My first choice would probably be molly bolts. Be sure to run this by the landlord. Plaster is not as easy to repair as sheetrock.

Subaru
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said by quitaccount:

said by Subaru:

Well I now know how thick the ceiling is.. had some work done so I'd say it's about 1/2" or so.

.........so it's cement board on studs? if so, get the stud centers and mount two 2x4's spanning at least two studs, spaced so the projector will fit over them, and fasten your projector to the 2x4's.

You don't really understand I had exhaust fan installed in the bathroom which required a square hole cut so that's how I was able to see the thickness..

the best way would to just use the tapcons.

robbin
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robbin

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So what is the ceiling made of? Did you take any pics? Do you have the piece that was cut out?

Subaru
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Subaru

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Yeah I will get some pictures in a few, it's hard to say I'm not sure how laying concrete for a ceiling is and what they use for a base but it looks like it was poured.

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said by Subaru:

You don't really understand I had exhaust fan installed in the bathroom which required a square hole cut so that's how I was able to see the thickness..

the best way would to just use the tapcons.

I do understand. I also know the entire ceiling can't be floating from only the perimeter of the room. there must be studs holding the 1/2" thick material or it would simply collapse.

tapcons are great in concrete----not so much in cement BOARD.

Subaru
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Subaru

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When the hole was open I did not have time to peak above and look around that might be a little hard to do now since the exhaust fan is installed and all.

but here is a picture.

Looks like it might be cement board? It has a wire screen above it from what I can see.


robbin
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Leander, TX

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Just as I guessed -- it's plaster on metal lath. Use molly bolts.

John Galt6
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John Galt6

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said by robbin:

Just as I guessed -- it's plaster on metal lath. Use molly bolts.

This. ^

For best results, make the holes carefully. You don't want to blow out the backside of the material by just hammering something through it. Doing that disrupts the integrity of the material surrounding the hole and reduces the support capacity.

robbin
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I wouldn't even use a hammer drill on it. Tape off the spot you want to drill so it doesn't chip out too bad and use a masonary bit in a regular drill at a slow speed. Start with a smaller drill bit because if you start with one sized for the Molly bolt guaranteed you will find the joist and only need to use a screw.

AVD
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said by quitaccount:

i have a hilti te-7c. it will drill into anything, including steel water pipes

Cutting steel is easier than concrete.
AVD

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said by MaynardKrebs:

Watch out for electrical conduit embedded in the concrete (not knowing what the 'ceiling' is the floor of above you).

How thick is the ceiling slab? If it isn't really thick (8"+), don't use expanding anchors - use Tapcons, or threaded rod anchored in epoxy. If using rods, use lock nuts to hold the projector onto the rods.

i would never use chemical anchors in tension.
MaynardKrebs
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MaynardKrebs

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said by AVD:

said by MaynardKrebs:

Watch out for electrical conduit embedded in the concrete (not knowing what the 'ceiling' is the floor of above you).

How thick is the ceiling slab? If it isn't really thick (8"+), don't use expanding anchors - use Tapcons, or threaded rod anchored in epoxy. If using rods, use lock nuts to hold the projector onto the rods.

i would never use chemical anchors in tension.

He's talking about installing a 12lb. load with probably 3-6 anchors locating in a relatively small area (almost certainly less than 1 sq. ft., and more likely about 1/2 that area). That many expansion anchors in that small an area is just asking for cracking & spalling of the concrete.

PeeWee
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Madera, CA

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There is a high likelihood of asbestos in that type of ceiling.

Subaru
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Subaru

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yeah that could be a possibility

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said by AVD:

said by quitaccount:

i have a hilti te-7c. it will drill into anything, including steel water pipes

Cutting steel is easier than concrete.

yes, with the proper tools. I am in construction and work with both daily.

it was a hammer drill bit (sds+ to be exact) that was put through the standpipe LOL.