Putting screws into bathroom grout

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neb

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#224383 15-Nov-2017 15:22

I've recently replaced the towel rails in the bathrooms (see: Cowboy builders, previous messages), and in one of them need to put screws through the grout, which is backed by gib. Problem is I want to avoid drilling out a huge amount of grout to fix a wall anchor, I've got the screws into a stud on one side but the other side of the rail is nowhere near a stud. Before I resort to drilling a huge hole for an anchor, does anyone know of any anchorless screw attachment techniques? The universal advice is "use an anchor", but this is a situation where it's not terribly practical to put one in without drilling out an excessive amount of grout.

My ad hoc solution, which no doubt will be decried as cowboy work by the next owner, is to squirt in some silicone filler to hold the edges of the gib together and then put the screw through that, but I'm wondering if there's a better option.

Oh, it doesn't have to carry a large weight, the side that's screwed into the stud takes care of that, just not wobble or feel loose.

neb

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#1901355 15-Nov-2017 15:35

Replying to my own question as a sample answer, the Cobra Triple Grip anchors are one example of a works-but-doesn't-work solution, you need to drill a 6.5mm hole for a 3.5mm screw. It's also not clear from the specs whether the depth of up to 16mm will deal with 10-13mm gib + tile/grout thickness.

wellygary

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#1901357 15-Nov-2017 15:39

The side that is not going in to the stud will eventually become loose, and the screw will probably work its way out,

- This could take years, or if there are kids or other unforeseen pulls on the rail much, much quicker,

Tou can get some pretty low profile anchors these days,

Surely the fitting on the rail will cover any screw holes?

neb

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#1901361 15-Nov-2017 15:43

wellygary:
Surely the fitting on the rail will cover any screw holes?

Sure, there's enough coverage that I could probably put a dynabolt in it, however it's really flaky grout (cowboys again, I think they just mixed up a bag of sand and cement and went at it), and the bigger the hole, the more of it flakes and falls away. So it's not a visual problem, it's a structural one, I want to minimise the amount of grou^H^H^Hmortar I drill out.

wellygary

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#1901364 15-Nov-2017 15:52

neb:
wellygary:

Surely the fitting on the rail will cover any screw holes?

Sure, there's enough coverage that I could probably put a dynabolt in it, however it's really flaky grout (cowboys again, I think they just mixed up a bag of sand and cement and went at it), and the bigger the hole, the more of it flakes and falls away. So it's not a visual problem, it's a structural one, I want to minimise the amount of grou^H^H^Hmortar I drill out.

Try to move the hole at the other 1-2cm ( and remain on the stud) and drill the tile?

neb

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#1901367 15-Nov-2017 15:58

wellygary:
Try to move the hole at the other 1-2cm ( and remain on the stud) and drill the tile?

It's a complex mosaic, not fixed, flat tiles. Drilling into the mosaic fragments isn't an option...

mdf

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#1901455 15-Nov-2017 20:55

Any chance you can make a hole on the other side of the wall? Say it's in a wardrobe or something?

Only other option that occurs to me is one of the 3M command range of products; I've been surprised at how much some of these hold.

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blakamin

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#1902467 15-Nov-2017 21:45

What about toggles?

(not these ones as they're countersunk, but you get the idea)

https://www.bunnings.co.nz/ramset-spring-toggle-countersunk-1-8-x-50mm-20pk_p00207454

SepticSceptic

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#1903171 17-Nov-2017 11:24

Thought about using an epoxy based fastening ? Some like Selleys Knead-it ?

Roughen up the tiles and grout - even some good deep scratches or holes on the tiles that will be covered by the rail fitting - you will need a good purchase for the epoxy to really adhere.

neb

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#1903232 17-Nov-2017 14:10

SepticSceptic:
Thought about using an epoxy based fastening ? Some like Selleys Knead-it ?

That was the thinking behind my silicone filler kludge, only the silicone is soft enough that I'm not driving the screw through epoxy. Here's a photo to provide a bit more perspective (note the tiny size of each fragment).

At the moment I'm leaning towards trying to drill the holes out a bit larger to fit the thinnest wall anchor I can find.

Bung

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#1903329 17-Nov-2017 16:00

If your preferred hole location coincides with a piece of tile you can get diamond core drills eg 6,8,10mm <$20 that would cut through the tile.

SepticSceptic

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#1903415 17-Nov-2017 19:12

neb:
SepticSceptic:

Thought about using an epoxy based fastening ? Some like Selleys Knead-it ?

That was the thinking behind my silicone filler kludge, only the silicone is soft enough that I'm not driving the screw through epoxy. Here's a photo to provide a bit more perspective (note the tiny size of each fragment).

At the moment I'm leaning towards trying to drill the holes out a bit larger to fit the thinnest wall anchor I can find.

If you squeeze epoxy into some drilled holes, say 50% larger than your fastening screws, you can easily drill into the set epoxy with your standard rail mounting fancy screws.

Quite a standard procedure for fastening boat decking accessories into wood / fibreglass.

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neb

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#1903505 17-Nov-2017 22:58

SepticSceptic:
Quite a standard procedure for fastening boat decking accessories into wood / fibreglass.

Ah, interesting, didn't know about bonding fasteners... so it looks like a female threaded collar epoxied into the gib could do the trick, and I'll just put a machine screw into that.