Thermal bridging and wall fixings

I don't understand the question. Fixing things to the inner leaf is not going to bridge the cavity. Am I missing something?

Not enough info. Is this on an outside wall? If it is,m what is the current insulation level? You can certainly fix a shower head holder to a piece of tiled plasterboard as all mine are like that with no issues Tiled plasterboard is very strong in shear - parallel to the wall face.

And because its tiled, if you use a proper diamond core drill to drill fixing holes, the screws wont pull out either. The mots likely failure cause is pulling the entire wall down. Yiou might just do that if you slipped an grabbed the shower head or shower curtain

Yes (not heard of an internal cavity wall!)

Slight - cavity wall insulation, and foam backed (18mm) PB.

Well, it sounds a bit overkill, but I'd rather drill into the wall and use a suitable fixing.

No - thermal bridging. Such as it is, the thermal insulation will be bridged by the screw.

But I'm also interested in general.

Sell let me assure you it IS over kill. But if you must, simply build a cardboard box, behind where the fixing point is and expose the outer wall and fill it with car body filler. Structural strength and insulation do not go hand in hand. Or use a wood block.

Whatever you do is going to men removing tiles anyway. Which is what you would have to do if you pulled the thing down having mounted it to the tiles as I suggested. So my advice is a shot to nothing.

You haven't understood the answer

I assumed you had a plasterboard inner and a blockwork outer. If you have a blockwork inner that is tiled, there is a perfect surface to connect to anyway

In all cases connect to the inner and leave insulation in place.

I think you will probably find your insulated PB already has a couple of screws to hold it in place during installation the adhesives used are not exactly instant grab. What is of more concern is that you will have in effect a “dot & dab” wall and ordinary screws and plugs simply will not do.

I suspect you will need specific fixings such as;

It is dot/dab. And not a very good job it's done either - coming away in a few places

Yes, got plenty of those, and probably what I'll end up using.

Oh I don't expect it to be much at all, and really I should have designed out the problem before I tiled. Just curious if there is such a thing as non-thermally conductive fixings, other than the ones that fix insulation materials.

Er, yes - overkill I think!

No, I'll simply drill the tiles, and use some 100mm metal wall fixings. They'll bridge the insulation, but hey.

OK - I was never concerned about bridging the cavity. Even I am hardly likely to drill through 2 courses of engineering brick to hold up a shower curtain rail . . . my concern is/was bridging the insulation between the thing being fixed, and the inner brick cavity wall.

It's a cavity brick wall. The inner is: brick, insulated PB, 6mm insulated tile board, tile.

Which is probably what'll happen. Just wondering if there is such a a thing as a medium/heavy duty method of fixing that doesn't bridge insulation.

For a couple of fixings I don't think you have anything to worry about.

A regular wall plug will give you some degree of thermal break - the screw will contact with the plug not directly with the masonry.

You'll still get some bridging because the point of the screw typically goes past the end of the plug, but maybe you could use extra long plugs in a deep hole to avoid that happening (or short screws in a regular plug, if that'll hold whatever you're hanging).

The kind of insulation fixings:

The only time I'd worry about thermal bridging here is if the blockwork is cold enough that a cold screw may act as a nucleus for condensation (and hence mould). If the cavity is filled that seems less likely.

Theo

I have some 5/16" nylon bolts

Thanks, food for thought. I think I'll just use some normal screws!

That was the sort of thing I was thinking about - if strong and long enough, and it's a bit late for me to think about a bolt (just tiled).

But there doesn't seem to be an available product - maybe because the problem's not considered to be that large, and/or if anyone cared enough they'd design in a solution that'd avoid the need for such fixings.

I'm not sure how strong nylon bolts would be - would the threads tear out under heavy load?

Another option is to bury the bolts deep and then fill the hole in the insulation with some kind of insulating medium. Expanding foam is one option, but maybe some of the more plasticy fillers would have an acceptable U-value?

Theo

They will if its plated with tiles. Tiles make an amazing strong wall.

Indeed. Sio thats three possible wall constrictions none of which you have clearly specified

- single brick with dot and dabbed insulated plasterboard

- cavity brick./block with foam infill plastered over

- single brick with internal studwork, foam infilled, plasterboard over.

I reality if it's tiled, the answer is simple,. Diamond drill the tiles, add plastic rawlplugs and Robert is a relative.

All my bathrooms are like that, none have failed in 22 years...

Blimey. Just drill the f****ng tiles and use plastic rawlplugs. You are way over thinking this

I give you stud wall, plasterboard over, tiled, drilled and plastic rawlplugs...