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Old 06-19-2016, 11:33 AM   #1
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Finding solid wall behind tiles to mount pedestal sink!

Not sure where best to post this, could belong to plumbing, tiles, masonry, here goes.

Started out as a super simple project of mounting a pedestal sink. Which involves anchoring the pedestal to the subfloor and the sink to the wall. This is on concrete slab and an exterior concrete block wall, so my idea is to just mark where the two mounting holes are on the wall and the one on the floor, drill the holes through the wall tiles to the concrete block wall, and the single hole through the tiles to the slab and fasten with 1/4" Tapcon screws. Simple enough.

The first issue I ran into was the really hard and dense porcelain tiles. My masonry bit won't even make a dent. I then switched to 1/4" diamond hole saw bits and they worked much better, but still end up consuming 1 bit per hole, but I got the three 1/4" hole done (one for the floor and two for the walls). Then I switched to hammer mode with my Tapcon bit and drilled into what's behind.

For the floor, I found solid concrete under the tile and drilled my 3/16" hole for the 1/4" screw. No problem.

For the wall, I hit a "wall". You know what I mean, my masonry bit went through different materials as I went deeper and deeper. From the finished porcelain tile, I went through about 4" of "stuff" before I hit the actual concrete block wall.

As best I can tell, behind the 3/8" porcelain tiles laid by the last owner, under that is a 1/2" layer of cement board, behind that is 3/4" of empty space, which is to be expected because it's furred out...then I ran into a layer of ceramic tile, which the bit went through easily but spitting out reddish brown dust, under that I believe a layer of 1/2" sheet rock, then another inch or so of void (furring?), then the concrete block wall. I switched to the longest 1/4" Tapcon bit I have which is 5.5" and drilled until it bottoms out.

So basically, from the front of the concrete block to the front of the finished porcelain tile is about 4" of stuff and voids. The longest 1/4" Tapcon screw is 5". The pedestal sink mounting hole has a thickness of about 3/8", which means the deepest I can sink the 5" Tapcon screw is about 4-5/8"...that is only biting into the concrete block wall about 5/8".

The entire bathroom is tiled wall to ceiling, so I am not going to tear out the whole bathroom to eliminate the extra layers.

Yet I am not too confident about mounting a pedestal sink on a wall using two 5" screws where only the last 5/8" is biting into something structurally solid.

I am aware that most likely this is OK because the weight of the sink is actually on the pedestal and not the wall, and I have even seen some people mounting those sink using toggle bolts on sheetrock...but still I like a more secured solution is there is one.

I have looked at the Tapcon web site and they do have a 6" screw but it's 1/2" diameter. That won't do because the sink mounting holes are smaller than 1/2" diameter, besides, I doubt I can easily enlarge the 1/4" holes I already drilled going through those diamond hole saw bits.

I am wondering are there any products out there, like a bolt hanger for wood, but a long one for concrete? One side can be screwed into the 3/16" concrete block holes, the other side sticks out of the finished tiles by about 1/2" to 1", and I can mount the sink on then tighten down with a washer and nut?

or use the 5" long 1/4" Tapcon screws, just apply tons of adhesve caulk to the back of the sink where it meets the tiles, and let the wall adhesive, the two tapcon screws on the wall and the floor pedestal do their joint duties to hold up the sink?

Or other ideas?

Last edited by miamicuse; 06-19-2016 at 11:45 AM.
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Old 06-19-2016, 03:16 PM   #2
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Re: Finding solid wall behind tiles to mount pedestal sink!

3/8" tiles on 1/2" cement board will be fine with some toggles...unless of course this is a frat house with toga parties every weekend.
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Old 06-19-2016, 06:23 PM   #3
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Re: Finding solid wall behind tiles to mount pedestal sink!

You could drill all the way through the concrete block and use threaded rod on a toggle bolt end, if in fact you are inside the block.

Personally I would hit that empty space with the toggle and be done with it.
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