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Old 10-24-2003, 07:15 PM   #1 (permalink)
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Location: AWOL in Edmonton
The support strength of drywall

I've been trying to hang a metal kitchen rack in my kitchen. However, I've discovered that underneath the drywall, I hit concrete. Solid, rebar filled concrete that destroys tapcon bits and concrete screws alike. I have an estimated thickness < .5-.75 inch drywall, and a maybe little air space between the back of the drywall and the concrete. I'm not certain the ratio of air-drywall, or if there is air at all. Holes in the drywall stop at almost exactly .75 inches deep.

Can I get 3/4 inch anchors and how much weight will the drywall with anchors hold?
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Old 10-25-2003, 08:00 AM   #2 (permalink)
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Can't you get a concrete drill bit and drill a pilot hole into the concrete?
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Old 10-25-2003, 08:19 AM   #3 (permalink)
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Location: Pacific NW
Are you using a good quality concrete bit with a hammer drill?
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Old 10-25-2003, 09:34 AM   #4 (permalink)
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Location: AWOL in Edmonton
I have established that drilling into the concrete is not an option. I used good quality bits and a professional grade makita hammer drill. "Solid, rebar filled concrete".
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Old 10-25-2003, 05:04 PM   #5 (permalink)
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Location: East Tennessee
Rent a construction quality rotary hammer drill and a bit for it that will correspond to an anchor by the company called redhead it is basically a piece of threaded rod with a sleeve on one end that when put in the wall spreads out as the nut is tightened up.

The milwaukee is the best bet for drilling it will drill in new concrete and concrete that has cured for 50 yrs. It hits harder and at a slower pace than most consumer hammer drills (that has a smaller hit and way to fast speed) the right drill will drill it so well you will be mad that you had to pay for the rental cost for a minute of work.
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Old 10-25-2003, 07:56 PM   #6 (permalink)
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Location: Lowerainland BC
I'd rent a concrete drill like Mvassek said and hang the thing properly. Old concrete can be amazingly tough to get thru, but it's easy with the right equipment. Tell the guys at the rental shop what you want to do and they'll set you up. Ask them for the correct anchor bolts too, they should have them. Your wall won't have so much re-bar in it that you won't be able to set some bolts.
Hung right, you should be able to swing from your kitchen rack.
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Last edited by splck; 10-25-2003 at 07:59 PM..
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Old 10-25-2003, 08:00 PM   #7 (permalink)
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Location: UCSD, 510.49 miles from my love
drywall? the only thing Id trust drywall to hang at a perpendicular angle would be those self-adhesive glow in the dark stars, man...

Drill the concrete and set an anchor, thatll last for centuries, and you wont even have to worry about the drywall..
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Old 10-26-2003, 03:55 PM   #8 (permalink)
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Location: AWOL in Edmonton
Last weekend, after ignoring the grey area in the condo bylaws, I rented a proper hammer drill and made a valient effort. Chewed through more bits then concrete. I was able to get through some of the concrete, but hit rebar (or exceptionally solid agregate) and could go no further, even with a fresh bit. So I patched the drywall and did some touch up painting. I then decided that drilling was not an option.

Home Depot has numerous anchors that are designed to hold in 5/8 drywall-gypsum. I've had a pair of (small but heavy) speakers mounted in nothing but drywall for about a month now. I wouldn't trust old brittle 3/8 drywall to hold up a calander. However, nice new thick material must have some significant support strength.

I am still wondering how much I can safely hang. I haven't been able to get a solid figure out of google, let alone a first-hand account. It's great to get numerous responses, but redundant replies that ignore the question don't really help.
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Old 10-26-2003, 03:58 PM   #9 (permalink)
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Location: UCSD, 510.49 miles from my love
a metal kitchen rack....
with metal kitchen implements....

I'd build another cupboard or pantry before I mounted anything with that kind of prospective weight in drywall of any thickness...

However, make sure that if you do actually mount the rack in the drywall.. that you test it with at least your body weight to see if it will hold, if it doesnt, its not worth the risk. Drywall isnt very reliable, so Im not sure how you would get an accurate strength reading any other way.
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Old 10-26-2003, 05:38 PM   #10 (permalink)
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Dude! You need to find what the sheetrock is hanging on. Usually it is a metal piece called "Z" channel. I have seen it installed both vertically and horizontally. I would guess horizontally, every 16" on center. Use a stud finder or use a thin finish nail to probe. You will hit metal within 14.5" of wherever you start (unless it is 2' on center). Z channel is similar to metal studs. It is fastened to the concrete with powder actuated tools and the sheetrock is simply hung on it with regular sheetrock screws. You can use sheetrock screws to mount to it but a heavier, thicker self tapping sheetmetal screw would be stronger. These are the kind with the end that looks like a drill bit and hex head. If you need to hang something on sheetrodk that is heavy then use large toggle bolts and/or a wooden ledger piece that is glued on with maxbond/liquid nails type adhesive.

Believe me, the sheetrock isn't suspended in mid-air by magic. It is hung on metal elements that are attached to the concrete...
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Old 10-27-2003, 07:31 AM   #11 (permalink)
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Keep in mind, when using a hammer drill in "rebar" reinforced concrete. It is not impossible to screw the bit onto the rebar. This leaves you with a permanently installed bit in your wall/floor/ceiling. (trust me, it does happen )
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Old 10-27-2003, 05:07 PM   #12 (permalink)
it's jam
 
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Location: Lowerainland BC
Quote:
Originally posted by jbrooks544
.

Believe me, the sheetrock isn't suspended in mid-air by magic. It is hung on metal elements that are attached to the concrete...
...and they used a hammer drill to install them
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