Steel columns and beams

[akist]

Hi guys,

I have a lot of steel columns and beams in my house from ground level all the way to roof ridge.

The plasterers who visited recently said that steel columns that stick out of the walls should be boxed in with fire rated plasterboard. They did not know how it should be for other columns and beams (ceilings, roof, dormers etc). The engineering plans are silent on this front, and do not wish to disturb the engineers.

I am inclined to simply noggins + ply + plasterboard whatever steels are visible.

Does anyone know what you are meant to do when the house has steels in it?

 

[Bouy]

Provide fire resistance in accordance with Approved Doc B of the Building Regs , normal plasterboard as you propose

 

[Deleted member 174758]

I am inclined to simply noggins + ply + plasterboard whatever steels are visible.

Assuming steel I beams: 2 x 2in soldiers inside the webs, 2 x 1in laths onto the ends of the soldiers (flush to the faces of the steels) then board with PB. No need for plywood. Before boarding steels they are normally given a couple of coats of intumescent paint. Most of the time these days pink (fire rated) board seems to be specified by the S/E (belt and braces?) - 2 x 12.5mm layers. I have to say that I've not seen too many steels in houses, other than in conversions

 

[^woody^]

Before boarding steels they are normally given a couple of coats of intumescent paint

They are not. Intumescent materials rely on expansion to perform and if that expansion is hindered ....

Anyway the boards should provide the protection.

 

[^woody^]

fire rated plasterboard

All plasterboard is fire rated!

 

[freddiemercurystwin]

Assuming steel I beams: 2 x 2in soldiers inside the webs, 2 x 1in laths onto the ends of the soldiers (flush to the faces of the steels) then board with PB. No need for plywood. Before boarding steels they are normally given a couple of coats of intumescent paint. Most of the time these days pink (fire rated) board seems to be specified by the S/E (belt and braces?) - 2 x 12.5mm layers. I have to say that I've not seen too many steels in houses, other than in conversions

Steels should absolutely not be painted with intumescent paint and boarded, furthermore the plasterboard should be fixed to itself or to steel angle framing fixed to the steel, timber carcassing should not be used.

 

[Bouy]

All plasterboard is fire rated!

Normal plasterboard is fire resistant but is not tested/rated?

 

[noseall]

Normal plasterboard is fire resistant but is not tested/rated?

12.5mm = 1/2 hour fire rating. Adequate for escape purposes.

 

[^woody^]

Normal plasterboard is fire resistant but is not tested/rated?

30 mins for 12.5mm, 20mins for 9.5mm. Each with a 3mm skim, and only where every joint is backed up by timber stud/joist etc, otherwise double boarding is required.

 

[freddiemercurystwin]

I assume Bouy means specifically for steel column or beam encasements, for which ordinary white wallboard plasterboard has not (to my knowledge) been tested. Sure it'll likely be fine but nevertheless it remains untested (to my knowledge). Not talking about a column or beam hidden behind a ceiling or partition but actual encasements. Sure Mr BCO may be satisfied but technically he should not be.

 

[^woody^]

A beam encased in a 12.5mm/30 min PB is no less protected than one "encased in a floor void with 12.5mm/30 min PB ceiling.

The concern would be in the fixing of the PB to the steel so that it does not just drop off in a fire.

 

[freddiemercurystwin]

Perhaps but as it has not been tested in that specific way it should technically not be built that way, unless the manufacturer is prepared to assess it and deem it acceptable (effectively taking on the responsibility). If a particular board has not been tested for beam encasement then Building Control are under no obligation to accept it. that's not to say common sense is likely to prevail and it probably would be accepted.

Try phone up British Gypsum and ask them to agree that encasing steel beams in ordinary plasterboard will provide the necessary fire protection and to put it in writing. They won't.

 

[Deleted member 174758]

They are not. Intumescent materials rely on expansion to perform and if that expansion is hindered ....

I am quoting from my obviously limited experience

 

[Deleted member 174758]

Steels should absolutely not be painted with intumescent paint and boarded, furthermore the plasterboard should be fixed to itself or to steel angle framing fixed to the steel, timber carcassing should not be used.

Want to tell the S/Es who specify this, then? We install to their written instructions, prepared drawings and GAs

BTW, ever tried fixing plasterboard to. Itself?

 

[mikeey84]

My BCO requested fireboard, but I've heard of BCOs accepting 2 layers of "normal" PB

Best to ask what they would accept- saves any hassle