Best hollow-wall fixings through tiles?

That's a nice tip; thanks.

I agree that this is the ideal solution, the practical drawback being that access to the inside of the walls can only be obtained by removing the plasterboard on the other side, necessitating a pretty extreme job of replacing, replastering, and repainting. Plus the fact that though this is perfectly possible on one side of the shower, the reverse of the wall on the other side is far less accessible. Probably worth the effort, though, if finding and using the studs doesn't prove practical.

I'd say a grab rail needs to be fixed to something a lot stronger than plasterboard.

If you have access to the other side, remove a bit of that plasterboard and fit a decent noggin between the studs, and fix through the tiles to that.

I fitted a vertical one to my shower cubical fixed into a stud. In practice, it's OK to use. For me, mainly to hang on to while washing one foot at a time.

This does seem to be a popular suggestion, so thanks.

It's a bit like mounting radiators or anything else at grabbing height. If you trip (or whatever) it's a natural response to grab the nearest thing. So I like to make sure it can take the weight.

In this particular instance that would be possible only on one side of the enclosure, since the other is half height and topped with glass.

I think that's exactly the sort of use envisaged: an aid to balance rather than a quick-grab resort in the event of a possible fall.

old loudspeaker or DC electric motor

That may be what's envisaged, but it does need to have the strength to withstand someone slipping and grabbing it to stay upright or at least slow their fall, because someone starting to fall is going to grab whatever they can.

I got a bit interested in this and went looking for the strength of tiles.

It looks like even crappy roof style tiles are around 10,000 psi for pure compressive loading

Assuming te full weight of a human is going to end up on a surface are of say 1/4" thick by 1/4" rawlplug diameter that's one sixteenth of square inch so the stress of say a 15st hulk (210lb) at 3,360 psi is not going to break the tile What that means is that you can stand on a 1/4" square piece of metal on a tile and not break it if its supported from below, and that actual compressions strength on a properly grouted wall is simply not a problem.

The obvious failure mode is that you pull laterally and the whole plasterboard wall collapses. Because that is plasterboard covered in tiles in TENSION.

and its about ten times weaker in tension, but again that tension will be spread out over the entire height of the wall, not 1/4" square.

Could a man support his weight on - say a horizontal batten screwed to a bit of 400mm wide plasterboard, fastened with plasterboard screws to a couple of studs?

I think he could, especially if covered in tiles.

In the end its a rather nasty version of a centre loaded end supported beam, of rather broad width.

the failure mode here would be the plasterboard giving way along a grout line.

Now the formula for a beam failure is that the tensile load in the face of the beam where the pull is, should not exceed the tensile strength of the material, and for a 16" wide bit of plasterboard of say 6" width

What does THIS mean. It means you cant support a 15 stone man on a 6" wide strip of plasterboard ceiling on 400mm studs no matter what the attachment is.

Its doubtful even on an infinite width.

So the engineering problem is now what sort of attachment, but whether or not the wall itself can stand the load under ANY sort of attachment

It is absolutely clear that a vertical load is AOK. the plasterboard and ceramic composite is well able to handle the load and the tiles will spread the stress concentration of a rawlplug just fine. What is now at issue is how much lateral load can the wall take before it tears off the studs and how likely a person grabbing for a handle would actually exter in that direction.

Her wqe can consider the reverse case - -a person falling AGAINST a plasterboard wall - will it break? My experience says it wont. That you need a club hammer to punch a hole in a plasterboard wall, leaning or falling against it is not enough .

What is the conclusion?

The first conclusion is that the type of fixing is irrelevant. Once the wall is tiled it has sufficient strength due to the tile to handle any sort of fixing, and my experience shows that whilst a plasterboard wall is crap at taking a rawlplug, a tiled wall is brilliant.

The second conclusion is that the plasterboard wall itself - not the fixing area - but the whole wall, is the weak spot from a lateral load. You wont pull the rawlplugs out but you might *just* pull down the whole wall section between the studs if you really really grabbed hard, or jerked on it while falling

I think its *really unlikely*, but if it bothers you the ONLY solution is to reinforce the plasterboard at that point and since that means going in behind it, you might as well add a noggin.

Personally I simply would not bother.

Especially since there is generally a horizontal noggin about halfway up a stud wall where you should be able to fix to it, or near it. That changes the stress equations dramatically The beam equations that apply are no longer 400mm load in middle supported at the ends, but a much shorter - the vertical distance to the noggin - end supported cantilever.

If you have such you dont need to fasten into it, just near it, and the job is done

You should be able to ID studs and noggins by tapping on the back side of the wall.

I still think you would have a hard job ripping the wall down. Because I can assure you that a rawlplug in a tile hole will not pull out

Many thanks for that: the details are fascinating.

This is nothing to do with structural strength and safety considerations, but I've seen it said (both here and elsewhere) that if a wallplug is inserted into a tiled wall such that the end of the plug is flush with the face of the tile (any lip or flange on the plug having been removed) then there's a danger that tightening the screw can cause enough lateral expansion in the plug to crack the tile.

It would be mildly annoying to successfully have drilled the tiles and then have that happen.

Never happened to me, but then I drill my holes exactly to IIRC 6mm using a diamond core drill (got it in homebase for less than a tenner) and use a red plug. I cannot emphasise enough how much better a diamond core drill is than anything else when attacking brittle tiles - ceramic or stone...

In practice all the expansion happens behind the tile - the screw generally has a plain portion of shank and the plug has a large diameter start section.

Experience has taught me to use exactly the right drill plug and screw. If you end up using a bigger plug, get the right drill for it. And use the right screw.

I have to say that no part of my house is actually done in plain cheap white 3mm thick 'trade' tiles. So I can't answer for those.

Thanks for the links.

Is there a difference between a diamond core drill and a diamond *coated* core drill? I ask because an earlier search turned up this set at what seems an astonishingly low price:

Wouldn't the forces depend on how the person slips or falls whilst hanging on the the grab rail/

I think they are the same - that small one looks exactly like what I have.

I would not expect them to last, so buy for the job only

Thanks. Does a 6mm core drill need a central pilot bit? Nothing seems to be included in that Amazon listing. I'll check elsewhere.

Shows the limitations

maybe not suitable for 3 closely spaced screws

Near the end other fixings are shown Also can be used with two screws in a straight line (see towards end of video)