Interior Wood Cladding and Fire Regs

[MikeGrahamT21]

Been thinking about different finishes for the vaulted ceiling in our new extension, and I've come up with the idea of timber cladding with gaps in between (a bit like what people use on the outside of buildings), think it will look nice in there, and a little different from the usual plaster.

 

Obviously the roof trusses are timber, and the insulation is PIR with foil face.

 

Question is, do I need to have any sort of fire retardant barrier behind the timber cladding on a ceiling? I've seen some on the web for about £100 a roll. I'd ask building control, but I doubt they would understand the concept of not using plasterboard lol

[Ian]

25 minutes ago, MikeGrahamT21 said:

Been thinking about different finishes for the vaulted ceiling in our new extension, and I've come up with the idea of timber cladding with gaps in between (a bit like what people use on the outside of buildings), think it will look nice in there, and a little different from the usual plaster.

 

Obviously the roof trusses are timber, and the insulation is PIR with foil face.

 

Question is, do I need to have any sort of fire retardant barrier behind the timber cladding on a ceiling? I've seen some on the web for about £100 a roll. I'd ask building control, but I doubt they would understand the concept of not using plasterboard lol

if it's a ceiling to the underside of the roof then it won't need a fire barrier rating however you would normally need a surface spread of flame rating- usually Class 1 for housing. Coatings and paints are available for treating timber to achieve these classifications.

 

Part B Building Regs reference document here. You need page 23 ono: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/485420/BR_PDF_AD_B1_2013.pdf

Edited January 22, 2018 by Ian

[Dudda]

I think the best option is to make the timber fire rated rather than a layer behind the timber. This will stop the spread of flames across the ceiling and can be done in two ways. Paint the timber with intumescent fire paint. You can get this in a limited number of standard colours and clear varnish. Custom colours are available but costly. You need to repaint this every few years to keep the fire rating. The other way is to get the timber pressure treated with a fire retardant. This is a much better solution as it doesn't require maintenance and you get a certificate from the manufacture that it's fire rated for your building control officer. 

 

From an aesthetic point remember the timber will make the ceiling look a lot lower than the traditional white plaster and it will make the room appear darker.

[nod]

1 hour ago, MikeGrahamT21 said:

Been thinking about different finishes for the vaulted ceiling in our new extension, and I've come up with the idea of timber cladding with gaps in between (a bit like what people use on the outside of buildings), think it will look nice in there, and a little different from the usual plaster.

 

Obviously the roof trusses are timber, and the insulation is PIR with foil face.

 

Question is, do I need to have any sort of fire retardant barrier behind the timber cladding on a ceiling? I've seen some on the web for about £100 a roll. I'd ask building control, but I doubt they would understand the concept of not using plasterboard lol

I’d fix a layer of plasterboard first

for the sake of a couple of hours and a few quid

It would make fixing the timber easier and take the spring out of your cladding I’m guessing your trusses are 600 apart 

[MikeGrahamT21]

5 hours ago, Dudda said:

I think the best option is to make the timber fire rated rather than a layer behind the timber. This will stop the spread of flames across the ceiling and can be done in two ways. Paint the timber with intumescent fire paint. You can get this in a limited number of standard colours and clear varnish. Custom colours are available but costly. You need to repaint this every few years to keep the fire rating. The other way is to get the timber pressure treated with a fire retardant. This is a much better solution as it doesn't require maintenance and you get a certificate from the manufacture that it's fire rated for your building control officer. 

 

From an aesthetic point remember the timber will make the ceiling look a lot lower than the traditional white plaster and it will make the room appear darker.

I'm guessing the treated timber will be hard to come by and expensive when I do. Varnish is likely the way to go with this one and re-treat and and when required.

 

Yeah I've thought about the aesthetic appeal, which to be honest is why I want to go down this route. Timber I'm looking at is 19mm x 38mm/50mm PSE, which ends up 14mm thick, so overall probably about the same as a plasterboard and plaster, no problems room looking darker, as its got a lot of glazing anyway.

 

Looking at a few of the treatments online, they all say effective for the lifetime of the timber, so sounds good to me

Edited January 22, 2018 by MikeGrahamT21

[MikeGrahamT21]

4 hours ago, nod said:

I’d fix a layer of plasterboard first

for the sake of a couple of hours and a few quid

It would make fixing the timber easier and take the spring out of your cladding I’m guessing your trusses are 600 apart 

 Yeah 600 wide, I think the timber alone will be fine, its never going to get touched once up so it should be fine.

[Nickfromwales]

You cant fix into the pb so I'm not sold on that idea. 

As has been said, if there's no habitable space above it's completely unnecessary. 

Best to find what FR coatings are available first in case they don't comply with the desired finish. 

[MikeGrahamT21]

2 minutes ago, Nickfromwales said:

You cant fix into the pb so I'm not sold on that idea. 

As has been said, if there's no habitable space above it's completely unnecessary. 

Best to find what FR coatings are available first in case they don't comply with the desired finish. 

Yeah its only a single storey extension, i'll do some more research on the coatings.

[Dudda]

 

18 minutes ago, MikeGrahamT21 said:

I'm guessing the treated timber will be hard to come by and expensive when I do. Varnish is likely the way to go with this one and re-treat and and when required.

 

Looking at a few of the treatments online, they all say effective for the lifetime of the timber, so sounds good to me

I'd be cautious any claiming lifetime or similar. I've used them in a few public buildings, halls, churches, etc which have exposed timber ceilings. These products need to be reapplied after a few years and the issue I see is how do you repaint the back of them? You're leaving gaps between them so the fire will go up between the gaps and light the back of these boards.

 

To be fair it's probably find for a small single storey residential property but no way I'd use that detail in a public building I'd have to sign off on. 

[MikeGrahamT21]

Found this one, which seems to fit the bill. No undercoat required (undercoats seem to be the most expensive)

 

http://www.fireproofspray.co.uk/flametect-c-wd-for-wood-clear-flame-retardant-68-p.asp

 

And you get a certificate with it for if BC ask.

[MikeGrahamT21]

Just now, Dudda said:

 

I'd be cautious any claiming lifetime or similar. I've used them in a few public buildings, halls, churches, etc which have exposed timber ceilings. These products need to be reapplied after a few years and the issue I see is how do you repaint the back of them? You're leaving gaps between them so the fire will go up between the gaps and light the back of these boards.

 

To be fair it's probably find for a small single storey residential property but no way I'd use that detail in a public building I'd have to sign off on. 

No i can appreciate that, don't think i'd want to either.

 

Timber is going to be screwed on, so I guess i could always unscrew it to repaint if needs be.

[MikeGrahamT21]

2 minutes ago, Dudda said:

 

I'd be cautious any claiming lifetime or similar. I've used them in a few public buildings, halls, churches, etc which have exposed timber ceilings. These products need to be reapplied after a few years and the issue I see is how do you repaint the back of them? You're leaving gaps between them so the fire will go up between the gaps and light the back of these boards.

 

To be fair it's probably find for a small single storey residential property but no way I'd use that detail in a public building I'd have to sign off on. 

Actually to stop this from happening, a fire retardant membrane behind should sort this out, which will kill the flames on contact, so may need a combination of both membrane and coating.

[nod]

2 hours ago, Nickfromwales said:

You cant fix into the pb so I'm not sold on that idea. 

As has been said, if there's no habitable space above it's completely unnecessary. 

Best to find what FR coatings are available first in case they don't comply with the desired finish. 

Bit of glue on the back wouldn’t hurt Timber will move at 600 centres once you get the heat on

[Nickfromwales]

40 minutes ago, nod said:

Bit of glue on the back wouldn’t hurt Timber will move at 600 centres once you get the heat on

Yup, but why fit pb when you could fit 9mm osb and fix wherever you like. . 

[JamesP]

I have a similar question, Vaulted ceiling which will be lined with 11mm OSB3 onto the rafters.  This is for racking, also on the internal walls.

We want to have birch ply sheets as a final finish, so do I have to fit plasterboard first, is it a fire regulation requirement? Or just fix straight onto OSB?

35 minutes ago, Nickfromwales said:

Yup, but why fit pb when you could fit 9mm osb and fix wherever you like. . 

 

[Nickfromwales]

15 minutes ago, JamesP said:

I have a similar question, Vaulted ceiling which will be lined with 11mm OSB3 onto the rafters.  This is for racking, also on the internal walls.

We want to have birch ply sheets as a final finish, so do I have to fit plasterboard first, is it a fire regulation requirement? Or just fix straight onto OSB?

 

Best to verify with your BCO but if your careful with fixing the plywood then couldn't that sort the racking and the finish with one product?

[bissoejosh]

On 22/01/2018 at 19:21, JamesP said:

I have a similar question, Vaulted ceiling which will be lined with 11mm OSB3 onto the rafters.  This is for racking, also on the internal walls.

We want to have birch ply sheets as a final finish, so do I have to fit plasterboard first, is it a fire regulation requirement? Or just fix straight onto OSB?

 

 

Did you hear back from your BCO regarding the ply roof? Apologies if I missed the post.

[tanneja]

On 22/01/2018 at 15:38, MikeGrahamT21 said:

Actually to stop this from happening, a fire retardant membrane behind should sort this out, which will kill the flames on contact, so may need a combination of both membrane and coating.

@MikeGrahamT21 did you go ahead with the wood clad ceiling in the end?  If yes, what approach did you take (sourcing pressure treated wood vs a fire rated coating, and then boarding option too)?

[MikeGrahamT21]

1 hour ago, tanneja said:

@MikeGrahamT21 did you go ahead with the wood clad ceiling in the end?  If yes, what approach did you take (sourcing pressure treated wood vs a fire rated coating, and then boarding option too)?

I didn’t, for ease I just ended up putting plasterboard up, the options for fire proofing became unclear and expensive, and I was short on time

[Dave Jones]

Save yourself a headache and fit it after you got a completion cert.