How to get at least 30min fire resistance in c1830 stud wall.

[crobar]

hi,

I am renovating an old house which has a mixture of brick and timber stud walls with Lathe and plaster. Some day, I might like to do a loft conversion. To do this I'm pretty sure I'll need the stairwell to be a 'protected enclosure' will all walls having at least 30min fire resistance.

In one of the rooms off the stairwell I've had to strip the old plaster from the lathe on the wall which is against the stairwell, but only on the inside, I won't strip the plaster from the stairwell side (it's been plastered not too long ago!). What can I do in this situation to get 30 min (or even better 60min) fire resistance for the wall?

I was thinking of stripping all the lathe off, filling the void with something and then screwing up fire resistant plasterboard and plastering?

I'm getting aerated concrete blocks for another job, would these work to add needed fire resistance to the void (plus sound resistance)? What else would be good?

Another problem is that there's cornice at the top of wall, so I can't fit plasterboard right to the very top as I don't want to destroy the cornice. There will be about 20cm of cornice, and a little bit of old plaster I can't remove at the top.

At the bottom of the wall there is a thick base plate which sits on top of the floorboards. The floorboards are on the beams with the spaces between beams filled with ash deadening.

Hope someone can help.

Thanks!

 

[Jadele]

12mm fire rated board and intumescent paint on the coving. You can double board to increase the fire rating.

 

[John D v2.0]

Last I checked just a normal board and skim both sides was already 30 minutes. You just need to worry about the doors and frames being fd20 after that. The plasterboard manufacturers should publish typical buildups online.
It's only when you start getting to party walls between timber frame flats you have to start doubling up fire board.

 

[^woody^]

Standard 12.5mm plasterboard and 3mm skim on one side of the stud will give 30 minutes on that side of the partition. But strictly, this will need a noggin or stud behind every board joint.

If you can't acheive this, then it will need to be double boarded (or overboarded), in which case you coud use 9mm board.

But in reality, 12.5mm board andf skim is normally accepted regardless - as long as the timber studs are adequate.

Typically, a partion must be considered as a whole to acheive a specific fire rating. But in this case, as the risk is from the room side rather than the landing, then the protection on the room side would be sufficient.

 

[crobar]

Standard 12.5mm plasterboard and 3mm skim on one side of the stud will give 30 minutes on that side of the partition. But strictly, this will need a noggin or stud behind every board joint.

If you can't acheive this, then it will need to be double boarded (or overboarded), in which case you coud use 9mm board.

But in reality, 12.5mm board andf skim is normally accepted regardless - as long as the timber studs are adequate.

Typically, a partion must be considered as a whole to acheive a specific fire rating. But in this case, as the risk is from the room side rather than the landing, then the protection on the room side would be sufficient.

Thanks I was confused whether I needed both sides to have the board in order to get 30 mins on either side, so it's definitely only one side needs done to get 30mins on that side? I'll check with building standards, but best to go in with a bit of knowledge.

 

[crobar]

12mm fire rated board and intumescent paint on the coving. You can double board to increase the fire rating.

Thanks, good tip about intumescent paint on the coving.

 

[^woody^]

Thanks I was confused whether I needed both sides to have the board in order to get 30 mins on either side, so it's definitely only one side needs done to get 30mins on that side? I'll check with building standards, but best to go in with a bit of knowledge.

As I mentioned, it is normally the partion as a whole that must be considered, not just the parts of it. But in your case, your argument is that the fire risk is from the rooms (and thats the whole idea of a protected escape route with fire doors), so the protection on just that side of the partition would be adequate.