Maximum Luminaire Weight Supported by Plasterboard Ceiling

[Toneyz]

I have never used them fixings that were on Dragons Den so cannot comment however they would only dissipate the weight over a small area. With a piece of ply/wood through the existing hole, the weight is spread over a larger area. This is the method that I have used before many times and never had a problem.

 

[Rpa07]

How can the noggin idea be rejected when they want a heavy luminaire and you have more experience than them? - beggars belief, some people’s attitudes!

Definitely the best solution, but I think the cut/restore ceiling option was also rejected.



No, I was (am?) looking for guidance on what the plasterboard itself can support, as it is always the plasterboard that fails rather than the fixing. I did think about those fixings but had forgotten what they were called so thanks for the link.

Thanks to everyone who has replied.

 

[telectrix]

ytou can fix with a 1" threaded bolt through the joist but you can't allow for fools ( and horses).

 

[Dave5678]

I've been back and weighed the light. The good news is that it's "only" 6kg, so just into the category of requiring support cables in addition to the flex.

Secondly, I've come across the following test video which has the test force in the appropriate direction. Not only does it show these fittings supporting a large force but that the plasterboard blows where the fitting is rather than cracking out to some other point. I know the structure holding the test device is narrower than the width between joists but I think the point still stands. With some reinforcement behind it to spread the load over a wider area (as suggested by Anthony) I think it is probably going to be quite safe, unless anyone can see a flaw in my thinking?

The Fischer website gives values for the fittings that are derated for safety to about half of those seen in the above test but still above (3x) the weight of the light. With multiple fittings the load is even further below the rating of a fitting.

 

[richy3333]

Can you not just use super long screws to pass through the cavity and screw into the laminate floor above? If the screws poke through the laminate just stick a book over the exposed dangerous point

 

[johnduffell]

Cut a 70mm hole in the centre of the ply (ply doesnt tend to split) then cut a slot from the hole to the outer edge of the ply. This enables you to put a fairly large piece of wood up the hole (if that makes sense

Nice ideai and I bet you love those metal or wooden puzzles you always get at Christmas where you have a load of impossibly shaped pieces and have to make it into an interlocking shape!

Can you not just use super long screws to pass through the cavity and screw into the laminate floor above? If the screws poke through the laminate just stick a book over the exposed dangerous point

Sounds like a joke but that actually happened when the shop below our flat fitted cctv monitor near the front door, a few nice sharp points looking through our carpet, taken off by the landlord with a grinder at our end and that's the job done!

 

[richy3333]

Oh my word that's crazy and also funny!

 

[mydigitalhome]

From memory it 10kg per2m max on plasterboard without noggins sure someone knows where I have seen it.

 

[Dave5678]

From memory it 10kg per2m max on plasterboard without noggins sure someone knows where I have seen it.

Thanks, that's a useful figure to know.

 

[Jjc]

Are there are any regulations/guidance on the maximum weight that a luminaire can be if it is only supported by the plasterboard ceiling and not fixed to any joists or noggins?

I have a customer who would like a (heavy, but currently unweighed) light fitting from their old house fitted in the new one, but examination of the existing pendant reveals that it is supported only by a circular dry lining box. The dry lining box has words stamped on it something like the following: "Warning. Ceiling determines maximum load. Max 3kg". Does this 3kg come from some official guidance or is it just something the manufacturer of this particular dry lining box has come up with?

The plasterboard is 15mm thick and the mounting bracket for the wanted light is wider than the dry lining box so the fixings would be into the plasterboard rather than using the dry lining box. The room above has a laminate floor so I have no access from above, only through the 70mm hole that has been cut out for the dry lining box. Potentially, I could feed some strips of ply into the hole to try to spread the load and then put wall anchors or similar through both plasterboard and ply, but at the end of the day it is still just the plasterboard that is taking all of the weight.

Is this job feasible or must the customer be restricted to lightweight fittings until such a time as the ceiling can be reinforced properly?

Common sense prevails here.