Dormer Cheeks built 30 years ago - No fire protection...

[Woody3]

I need to fire proof the dormer cheeks of a loft conversion on a mid terrace. The conversion was done in 1990.

Externally it's slate on battens, membrane, t&g boarding then studwork. Ideally Supalux board or similar should have been used, alas, it hasn't. Before I phone a couple of fire protection companies, is there a way around this without having to strip the slates off?

I was speaking to the Building Inspector and he says there might be a product out there that can be painted on the t&g boarding from the inside that soaks into the timber enough to give a 30min fire resistance.

Just wondered if anyone had solved such a problem before?

[Equus]

Yes, you can get timber treatments ( Example - though the factory applied, pressure-treated ones are more effective), but if you've got slates on the outside and (presumably?) plasterboarded studwork on the inside, I wouldn't be worrying too much, if I were you.

Edited to add: I've just re-read your initial post properly.

I'm not aware of any paint-on treatment that gives 30 minutes structural fire resistance. The product I linked above gives resistance to surface spread of flame which is a quite different thing.

I'd again question what you're trying to achieve: the normal approach would be to sheath the structure in materials with adequate fire resistance (plasterboard on the inside, slates on the outside) so the timber hidden inside the structure doesn't need any fire resistance in itself.

Edited by Equus on Thursday 31st August 09:07

[Cavey]

Try www.envirograf.com. Never had quite the same situation as yours but have used their products to uprate the fire resistance of, for example, old timber doors in Listed properties. They may have something which would do it.

Out of interest, why do the dormer cheeks need to be fire proofed?

[B17NNS]

Do you mean you have T&G as a finished surface internally? Can you not just overboard with pink boards?

[joshcowin]

We use this company and products https://envirograf.com/product-category/fireproof-...

Give them a call they will provide something!

[Woody3]

Thanks chaps - the Building Inspector actually gave me the contact for Envirograf - good to see they have been recommended from different avenues. I gave them a bell and they've given me a possible solution - they were extremely helpful! I'm just waiting to hear back from B.C to see if their solution is acceptable. I shall report back.

The t&g board is to the external side of the stud wall (battens and slates are then fixed to this).

The cheeks have to be fire proofed externally as well as internally if the boundary is within 1m. It's to stop the spread of fire from one dwelling to the next.

[Equus]

Woody3 said:

The t&g board is to the external side of the stud wall (battens and slates are then fixed to this).

The cheeks have to be fire proofed externally as well as internally if the boundary is within 1m. It's to stop the spread of fire from one dwelling to the next.

He's being very strict, then - most BCO's would accept that the slates themselves are fire-protecting the T&G (try burning a slate and see how far you get...). It's no different to having an untreated timber structure supporting a tiled or slated roof, when is standard practice everywhere.

But it sounds as though he's asking for surface spread of flame, not structural fire resistance, in which case the product I orignally linked is suitable.