And I thought downlighters were bad..... (PB fixing question inside)

[ProDave]

I have always hated fitting recessed downlighters.

But on todays job I have found some abomination of light fittings that must have been dreamt up by someone with a rather cruel sense of humour.

This is on a refurbishment following a flood, and everything specified by the architect, so no deviation, they have to be this particular fitting. (this is the refurb job that insisted on metal back boxes, so remember my thread, I bought those snap in ones, well I would NOT recommend them, they are rubbish)

So imagine a recessed fire rated downlighter with a GU10 lamp, but instead of it being recessed, it's surface mounted. So an aluminium tube about 100mm long and 60mm diameter (approximate, not measured dimensions)

The terminals are a bare choc block only ever so slightly recessed into the top. So for starters that's going to be fun looping two 1mm t&e's in and out. So that dictates a reasonable size hole in the ceiling to lose any spare wire. Handy as the builders have already drilled 1" "pilot" holes for me, bless them.

But the fixing holes to atach this thing to the ceiling are about 3mm diameter, two of them, but the ONLY access for the screw is remove the lamp and a long screwdriver through the tube of the fitting. So that's going to be one fiddly son of a ***** to even get some screw through.

But the biggest problem I face, is I need some suitable plasterboard fixings. Bear in mind that 3mm fixing hole, and that 1" pilot hole already in place, any PB fixing I fit will be close to the edge of that pilot hole so a risk of bursting the edge of the board.

And did I mention it's a double layer fire rated ceiling? but quite how this particular fitting maintains the fire rating beats me.

So any ideas of a suitable plasterboard fixing to do this? the usual ones I use, the metal screw in "redi driver" I think is too large.

I'm due to go back in a week to fit them. A job I'm not looking forward to. Bring back good old down lighters, at least they work.

 

[Andy™]

sounds a PITA. better you than me....

can you not drill another 2 fixing holes in the fitting? and maybe make them all 4mm to take an inch 8, then screw direct into the plasterboard? since its double boarded, you will have more plasterfor the screw to grip, and 4 of them so it shouldnt go anywhere

failing that, bit of wood through hole then dropped into place, and a longer screw to reach into it?

and surface fire rated sounds so wrong. get some pics for us to laugh at what they want

 

[NozSpark]

How about a piece of wood planted in he ceiling void and some 3" screws through?

 

[ProDave]

Interesting ideas there.

There's no access above to fit wooden backing, and being double layer, I think you would have to enlarge the hole far too much to insert anything from below.

I like the idea of just screwing into the PB with no "fixing" Anyone tried this, if so what's the best sort of screw to use? As you say, there's two layers, so 25mm of plasterboard to bite into. It would no doubt work once, but if you ever had to remove the fitting you would probably want to re fix into fresh holes.

I have some offcuts of PB in the garage, so I feel some experimenting with different screws fixed directly to see what works into some double layer test pieces.

I'll try and remember a camera for my next visit.

 

[Andy™]

ive done it loads of times. just dont go too crazy with the drill/driver where is gets too tight and rips the plaster from the threads

pretty much any screw would do the job, but try and get the thinnest scew with widest threads so extra grip

 

[SLIPSHOD & SLAPDASH]

Plasterboard screws ! Normally black like these Phosphate Twin Thread Drywall Screws 3.5 x 38mm Pack of 1000 | Screwfix.com

 

[kerching]

Don't know what they are called [helpful or what????]...but those metal-firerated-squash up-umberella type-compression jobbies. the ones you can fir in with a rivetting type gun. UniFix used to call them 'fast-brollies'. Mark ceiling, drill holes, fit fixing [leaves a threaded metal hole in ceiling] then fit 'deviant Architect's' fitting with a long diver bit in a cordless drill.

I refer to my previous ranting....Architect from the the Greek Archos [bloke] tectos [knows bu88er all]............. :coat

 

[wozz]

I would also like to see these amazing fittings! could you not drill out the fixing holes and use some 90mm or similar spring toggles?

 

[Graham Lister]

Just use a couple of red plugs!

 

[sparky b]

Just use a couple of red plugs!

Agreed, nothing wrong with a 6mm plug in a 5mm hole......

 

[ProDave]

Just use a couple of red plugs!

Might try that on my test pieces. Given that it's two layers, almost the whole length of the plug should be in PB.

Those compressible umbrella types are normally good, but I don't think they work on double layer board (unless there's a special longer version of them)

But did I mention the other problem, the fixing holes are quite close to the edge of the fitting, so if I used those, I think you would see part of the metal flange of the fixing showing outside the edge of the light.

So I'll try standard red plugs on my test pieces and see how they hold. I might also try a quick squirt of sticks like sh*t in the drilled hole before inserting the plug.

 

[Theorysparky]

What about these

they go straight into the board

Wall Dog Universal Screw.

 

[ProDave]

What about thesethey go straight into the board

Wall Dog Universal Screw.

That looks an interesting idea. I think the theory is the wide spaced thread is less likely to turn the PB to dust. That's very much like the thread profile of the Redi Drivers I use a lot.

 

[gordy71]

red plugs with 2 inch by 10 screws should bite nicely, just make sure the plug bites first!

 

[ProDave]

red plugs with 2 inch by 10 screws should bite nicely, just make sure the plug bites first!

Yes if I choose that option, then an under size hole (5 or 5.5mm, I need to test both) and then for good luck "glue" the plug into the hole with sticks like sh*t

I should be able to organise it to drill and glue in all the plugs, then leave for a while for the glue to set before screwing the fittings on.

 

[cadspark]

I use the uno rawlplugs which are better at gripping than the standard type.

 

[SLIPSHOD & SLAPDASH]

Skyhooks (No6)