Fire protection in cellar/basement

[Captain Howdy]

Hi all,

I have a property with a large cellar/basement. Both the electric and gas meters are located in the cellar. Long story short, I need to ensure 30 minutes of fire protection between the cellar and the ground floor, just in case a fire breaks out in the cellar. Building Regs people have suggested installing a ceiling in the cellar comprised of fire-rated plasterboard. Currently there is no ceiling there, only joists on top of which the ground floor floorboards are supported.

My issue with this is that boarding under the joists in the cellar will lead to damp/rot issues in the future, something which they have acknowledged. I suggested an alternative method of painting over the joists with intumescent paint. They won't give me a straight answer as to whether this would be acceptable. It leaves me a little stuck - I don't mind getting the boarding done. However, it doesn't solve the problem of condensation/rot issues. After all, even though there is limited ventilation in the cellar, the temperature changes there will still lead to condensation etc. Trapping this in the space above the fireboards will mess up the joists, I fear.

Just wonder if anyone else has had similar experience, or a better solution?

Many thanks in advance for any suggestions.

 

[freddiemercurystwin]

If the deck is floor boards, how will you prevent smoke from wafting up through the gaps in the boards? I would expect Building Control would accept some paint system provided you could back it up, that is you would need to contact one of the specialist paint manufacturers/suppliers and see if they will put their name to it, see of there is some fire tests that fit your set-up etc. My gut is there won't be any such fire tests but contact someone like Envirograf or Thermogaurd (speak to their technical departments don't waste time emailing) and see what they say and if they're prepared to provide you with the necessary evidence you can pass on to BC. Trouble with intumescent paints in houses (and everywhere actually) is that the next owner might slap some satinwood over it or won't bother checking the condition of the intumescent paint regularly as they should be or whatever, then the system has failed.

 

[Captain Howdy]

If the deck is floor boards, how will you prevent smoke from wafting up through the gaps in the boards? I would expect Building Control would accept some paint system provided you could back it up, that is you would need to contact one of the specialist paint manufacturers/suppliers and see if they will put their name to it, see of there is some fire tests that fit your set-up etc. My gut is there won't be any such fire tests but contact someone like Envirograf or Thermogaurd (speak to their technical departments don't waste time emailing) and see what they say and if they're prepared to provide you with the necessary evidence you can pass on to BC. Trouble with intumescent paints in houses (and everywhere actually) is that the next owner might slap some satinwood over it or won't bother checking the condition of the intumescent paint regularly as they should be or whatever, then the system has failed.

Many thanks for your suggestion. The ground floor is comprised of wooden floorboards. Point taken re: smoke.

I suggested intumescent paint to BC myself after looking into different methods of stopping the spread of fire. I came across fire-rated plasterboard, intumescent paint for timber, and also intumescent cloth membranes (these are impregnated with an intumescent chemical).

Glad you mentioned the above two brand names. i already reached out to Envirograf, who were very helpful. They sent me a bunch of reports on tests they had carried out, showing that when painted properly, a timber structure holds off fire for nearly an hour before failing. They also have a bunch of demos on youtube showing how their intumescent paint works. They have supported clients through loads of similar projects in garages and cellars.

I passed all this onto BC, but they gave a very vague response, saying this method is more commonly used on smaller areas, e.g. to fireproof doors. I even invited them to visit the property with my contractor present, in the hope he'd address any doubts they might have. No luck, in fact, BC have ignored me for a few months now, which is very disappointing. The last time I chased them over the phone, they said they were unsure about using intumescent paint, because they'd never seen anyone use this method for a cellar before, they've only ever seen pink plasterboard.

 

[freddiemercurystwin]

All plasterboard is fire proof to a certain degree. My point is you would need to present a set of documents including say a simple detail drawing specific to your situation with your property name, showing how the boards will be sealed somehow (still don't see how you can do that other than sealing the joints which seems open to failure) and the appropriate intumescent products & how they're to be applied alongside the product data sheets and test data proving this will work, including an official email from Envirograf or whoever you use stating that these products, if installed as per the drawing No. ... will achieve the 30mins, in short BC will want you to prove your system will work. If you have joists running parallel to a wall that are maybe 1/2" or so off the face of the wall, how will you protect that exposed side of the joist? Some sealant? Beacuse you won't be able to paint it. Which sealant? It needs to go on a drawing.

 

[Captain Howdy]

All plasterboard is fire proof to a certain degree. My point is you would need to present a set of documents including say a simple detail drawing specific to your situation with your property name, showing how the boards will be sealed somehow (still don't see how you can do that other than sealing the joints which seems open to failure) and the appropriate intumescent products & how they're to be applied alongside the product data sheets and test data proving this will work, including an official email from Envirograf or whoever you use stating that these products, if installed as per the drawing No. ... will achieve the 30mins, in short BC will want you to prove your system will work. If you have joists running parallel to a wall that are maybe 1/2" or so off the face of the wall, how will you protect that exposed side of the joist? Some sealant? Beacuse you won't be able to paint it. Which sealant? It needs to go on a drawing.

All good suggestions, and noted. Will put together a plan, and I'm pretty sure Envirograf can help on that front too. Just hope BC's engagement is better than I've experienced over the summer ...

Thanks again

 

[JohnD]

My issue with this is that boarding under the joists in the cellar will lead to damp/rot issues in the future,

Where did you hear that?

Do you mean the joists will rot? Or the contents of the cellar?

Is your cellar unusually damp and unventilated?

 

[Captain Howdy]

Where did you hear that?

Do you mean the joists will rot? Or the contents of the cellar?

Is your cellar unusually damp and unventilated?

I meant the joists. The cellar isn't especially damp, it's no better or worse than most others I've ever been in, i.e. smells a bit musty there. There's limited ventilation, i.e. there's a periscope-shaped vent that leads up from the cellar to a narrow grate in the front garden.

My understanding is that it's a common problem with ground floor joists, i.e. if there's poor ventilation, the cold temperature can cause the moist air to condense on the joists and rot them over time.

In my simple picture above, by installing a ceiling in the cellar, it would butt up next to the underside of the joists. I'd end up trapping moist air in the cavity between the fireboard and the ground floor floorboards.

 

[JohnD]

Fitting a ceiling provides a barrier between the cellar air and the joists. I favour foil-backed plasterboard which has a moisture barrier.

Condensation might occur if the surface was colder than the cellar air, but why would it be?

I don't believe it's a common problem.

You might consider improving cellar ventilation. You need vents on at least two sides of the house to provide cross-flow of air. A vent every two metres is not too many.

Sometimes the original ventilation gets blocked by later work.

 

[Captain Howdy]

Thanks John, that's reassuring. Will have a think about what more can be done to improve cross-ventilation.

Much appreciated.

 

[JohnD]

Slightly off topic, you can reduce heat loss in the rooms above by packing mineral wool insulation under the floor. Most of the heat loss is by draughts rising through the gap under the skirting at the edges of the room, so you can cure most of it bt stuffic between the joists round the perimeter. Draughts can also come up gsos between floorboards, but if you are fitting a ceiling, I don't think that will be so bad. I do all my floors if and when they are renewed, when it's not much extra work. The wool stuffs into irregular gaps so you don't need precision cutting, like with Expanded foam.

It will also block the fine dirt carried in the draughts, which leaves black lines on carpets.

 

[Captain Howdy]

@JohnD - Thanks for the suggestion. Actually, the guy I called over to give me a quote for the boarding job said pretty much the same the same thing re: insulation. Will definitely consider it.