Heavy duty cavity fixings

[DLaing]

I'm about to attach a heavy radiator (15 - 20 Kgs empy) to a cavity wall. I'm planning to use some very heavy duty wall anchors (M6 x 55). Any ideas if these are up to the job and whether the plasterboard can take such a load?

 

[murraysnudge]

I assume you are referring to a dry-lined block wall when you say cavity wall? The one reason I don't like dry-lining is when you have to fix things to it. I have recently been working on some dry-lined houses and what I do is mark the position of the radiator brackets and cut away the plasterboard. I then render the wall with a cement/sand mix flush with the plasterboard and when it is set I drill through into the blocks and use a nylon wall plug and No 10/5mm screw. The bracket is then fixed to something solid.
The radiators were originally fixed by using a pice of 15mm pipe as a spacer and screwing through to the blocks. I personally don't like the idea.

 

[AdamW]

Just to be on the safe side; it's not a stud wall is it? You can tell by knocking on the wall: if it is hollow, this is a stud wall. A stud wall is a wooden framework with plasterboards screwed onto it.

With a stud wall, the only reliable way to mount something heavy such as a radiator is to bolt it into the studs. These are the wooden uprights in the wall. In a new house they will be set at 400mm centres.

 

[AdamW]

I then render the wall with a cement/sand mix flush with the plasterboard and when it is set I drill through into the blocks and use a nylon wall plug and No 10/5mm screw. The bracket is then fixed to something solid.

I hope you are tapping those plugs back into the wall past your sand/cement!

 

[murraysnudge]

I certainly am Adam, that's why I said:

I drill through into the blocks

You obviously know that the expansion of the plug can split the render. I found out the hard way, years ago.

 

[ChrisR]

I've used bits of 2 x 1 behind the rad brackets cut into the plasterboard on dot and dab type dry lining - much quicker than the wet stuff.

Plasterboard- for heavy rads use 3 fixings per bracket and its usually OK Sometimes that means drilling extra holes in the bracket.

Lath and plaster - umbrella type fixings can be ok if you use lots, but it dependson the horse hair and muck they used on the particular wall. A 15mm sheet of plywood spanning the studs gives you something solid enough for short fat screws to hold the rad brackets onto. If the rad is a tall, short length DC on a poor wall, hack the plaster off and fix a board on top of the laths (or cut them out) spanning the studs.

On the rare occasion when its possible to adjust the rad position, you can fix ONE of the rad brackets straight into a stud, which helps.