Straw

[The Colonel]

Came across an interesting discovery whilst carrying out a fire risk assessment at a licensed social club this morning. A two storey building comprising;
Ground Floor; lounge bar, public bar, concert room along with all the usual areas cloak rooms, toilet, kitchen. First floor; Stewards flat with seperate entrance, entrance from club and alternate escape over roof and down metal stairs.

No problems so far! the beer celler is located under the public bar (basement) and accessed from within bar area with seperate shutte for barrels etc. Quick inspection reveals no problems until where new supply pipes to the bar area have penitrated the floor slab to ground floor there is also a 50mm slab of straw. The ceiling of the celler appears to be lined with a 50mm slab of compressed straw with  a thin plaster skim. Even the club secretary was unaware of this lining which may have been in place since the original building in 1920.

My initial reaction was oh heck Housten we have a problem, but the risk in this area is low with all new equipment and all sockets for pumps etc fitted with trips etc. Thinking about it now rather than ripping down what apart from two small areas is a reasonable ceiling under a concrete slab is to seal those exposed areas of straw with plaster or intumescent material and consider removal during any future refurb. Area of ceiling is about 4m x 8m.

The club has a type M fire alarm and I am recomending addition of some smoke detection to provide early warning to flat on 1st floor.

Any thoughts or have you come across this type of ceiling before?

[kurnal]

Is it plain compressed straw or is it bonded together with a glue or cement? There used to be a decking board called stramit made of straw. If its just compressed straw it was probably installed for insulation - they used to call it pugging between floor joists.
Is it a problem- not necessarily. After all if its protected by a plaster skim or ceiling then its no worse than some of the polystyrene slabs that were commonly used to insulate buildings.

[The Colonel]

Kurnal

Just seems to be compressed straw any adeshive probably disappeared ages ago, used to have a factory on my patch years ago that made the cement bonded type of slab. Pugging that's a blast from my recruits course when the West Mids lads thought us country folk were joking when we had buildings full of it on fire and that we only used it to bed down the horse's pulling the pumps.

My thoughts are cover any exposed areas and make sure that all contractors ans staff are aware of what is behind the plaster with signs etc

Just to clarify the straw slab is under the concrete slab and as kurnal points out was probalbly used as insulation for the celler

[AM]

There were some houses in my area that had straw insulation boards, that were constructed by housing associations as a result of the post war population increase. They were only supposed to be temporary, but are still being used, and there has been serious fatal fires in them, due to the linings being breached by continual renovations, rewiring etc - the linings collapse and you have a huge increase in fire load.

[kurnal]

Good point AM I have also heard of this. Whether the fire risk is any greater than unstopped lath and plaster walls I dont know. Had some scary moments trying to stop fires spreading rapidly within the wall caviity, remember one 4 storey victorian place with lath and plaster staircase,  opening it up to get water in only to see the paint blistering way above you. The plumber who started that one wasn't even insured.

[John Webb]

Could intumescent sleeves designed for surrounding pipes through walls be used here to cut off fire spread?
Or use intumescent paint to cover over the exposed straw?

[Tom Sutton]

Try http://www.stramit.co.uk/ providing the skimming is not breached its meets 30 mins FR and Class "O". The big problem is trying to achieve this in the real world, is very difficult.

[The Colonel]

TW

Thanks for the link very useful