Maintaining 30mins fire protection wall lighting

[MoDo]

Any suggestions as to how to incorporate recessed wall lights (Gypsum) in a stud wall that has to achieve 30mins fire resistance? The only way I can think of is to provide the 30mins protection on the 'outside' of the wall as the lights are only needed 'inside'. However I cannot find a fire test of any plasterboard which provides 30mins protection when installed on only one side of the wall.

 

All the tests seem to assume you'd use the same board on both sides - but then the recessed lights are compromising the inner face.

 

Fire rated recessed wall lights (for stairs) do not seem to exist. 

[Alan Ambrose]

There are ones for ceilings AFAIK - none for walls?

[BadgerBodger]

I think you will struggle with “certified” solutions. I’m having a nightmare with 120 minute fire doors, and general compartmentation issues. The various changes to building safety act, fire safety act, updates to building regulations, greater understanding and desire for compliance with BS9999 (among many, many other updates and changes) since Grenfell has resulted in a lot of things that were deemed “OK” to be shunned and a lot of companies are avoiding advising anything but the tested detail. 
 

What this means at a site level is that we can only install the precisely tested arrangements whilst maintaining warranties and many situations are untested. Case in point my fire doors. 
 

Back to your issue, in summary, there is a good chance there is no specifically tested solution for your problem. On the plus side, the fire risk would probably be deemed quite low in a domestic arrangement (albeit  elevated if you are talking about compartmentation - I’m imagining a protected corridor due to storey height) and it about an appetite for risk. I believe you’re right in that plasterboard wall test data is usually from one side which will give an overall rating for integrity and insulation (each serve different purposes). I’m not that well versed in domestics but I believe they are usually looking for integrity. It used to the rule of thumb that a 15mm standard plasterboard offered 30 minutes of resistance to fire (back when the discussion re integrity and insulation was less widely considered). I believe building regs also consider that 0.7mm piece of pressed steel will also provide 30 minutes of resistance… There are also proprietary product such as putty pads you could also consider however I’ve never actually seen them used in the way (generally for maintaining integrity to singe and double back boxes)

 

 https://www.firesealsdirect.co.uk/passive-fire-protection/electrical-protection/putty-pad-for-electrical-socket-box-single/?srsltid=AfmBOop5eF5txPnf8Eu2coCbUTECUQcTemyYIirljLIvWxRaPAHOcaR9

 

If I were going about it in my own build I would form a lined service opening to the required size in accordance with the relevant manufacturers guidelines (read British Gypsum white book or equal for competitors) but only cut out the facing board on the side I required the rebate. For 30 minutes  I’d add an extra board to the back of the rebate. 
 

Consider the arrangement in the photo for sockets, I can’t find the lined penetration detailing for some reason…
 

Of course, I would never recommend that you actually do this yourself.

[MoDo]

15 minutes ago, Alan Ambrose said:

There are ones for ceilings AFAIK - none for walls?

Yeah, there's almost unlimited choice of regular ceiling spots that are fire rated. But seems to be literally nothing at all for walls. Maybe something to do with obtaining a fire test or simply lack of demand.

 

8 minutes ago, BadgerBodger said:

I think you will struggle with “certified” solutions....

 

Thanks for your reply, it does seem a lot of this is due to everyone trying to cover their backs now, though admittedly I had no experience prior - this being my first self-build so can't really compare to anything prior to Greenfell. In my case I just have to satisfy the BC inspector. However as you say they just want a certificate for everything - but there isn't a certificate for everything. I've actually had to give in on our wall build-up and will be fitting a kilometre of battens to all exterior walls simply because the fire test certificate for the SIPS system we have was tested with this build up. Logically there is no little reason why a plasterboard wall would be safer with an extra 25mm timber between it than without - but that's where were at.

 

I spent ages looking at all sorts of putty pads and intumescent covers but there is nothing I can see that matches the size of the light fitting I wanted, which are 30cm high. Arguably being made of Gypsum the lights should be no less resistant than the plasterboard - and perhaps just a small piece of putty to cover the wiring hole would suffice - but it'd be up to the BC inspector I guess. Your idea of constructing a lined opening is probably belt and braces approach but quite a lot of extra work if there are say 16 lights!

[BadgerBodger]

Hmmmm, it’s really hit and miss how well receiving you BC officer will be! 
 

Have you considered closing the void with an ablative batt? It’s pretty cheap and cheerful and comes with loads of persuasive test data!!! 
 

 

[MoDo]

50 minutes ago, BadgerBodger said:

Hmmmm, it’s really hit and miss how well receiving you BC officer will be! 
 

Have you considered closing the void with an ablative batt? It’s pretty cheap and cheerful and comes with loads of persuasive test data!!! 
 

 

Can't say I'd ever heard of one until about an hour ago! Not sure how that would work? These are the light dimensions (below) but the wall build up is 12.5mm plasterboard (fireline), 15mm OSB on 100mm timber stud (at least I think it's 100mm), with another 12.5mm plasterboard on the 'outer' side of the stud. Would I just glue the batt over the back of the light with the approved sealant? I guess they are soft and would mould around the fitting?

 

[BadgerBodger]

They’re really firm, high density ROCKWOOL. It’s a fire stopping product generally used for closing voids or sealing around services with a compartment wall, floor or ceiling. There are other product from competitors such as Hilti, FSi, etc. It can generally be friction fitted (in your case horizontally between the plasterboard and osb to close the void) by oversizing the cut pieces by 5/10% but it can also be “patressed” with mechanical fixings. The joints and abutments are then sealed with the appropriate intumescent mastic. If we’re doing this at home I’d then fit another plasterboard to the rear of the pocket.

Its not a perfect solution but it should get passed by BC.. 

[MoDo]

Thanks, I think that sounds like a plan. It's a bit fiddly but as you say it should satisfy BC. Appreciate your advice.