1/2 hr fr ceiling

[nearlythere]

Anyone point me towards authoritive guidance that would describe how to apply plasterboard to provide ceiling of 1/2hr fr?

[SeaBass]

The PFPF purple book has some good data on fire resisting partitioning and ceilings. It can be down loaded free of charge from the PFPF website at http://pfpf.associationhouse.org.uk/default.php?cmd=210&doc_category=250   although you may have to register with the site before you can get access to the document.   

The following sites are product specific, but they give some decent information and confirm the FR properties of single layer  and over lapped double layers  of skimmed plaster board.
http://www.fireplasterboard.co.uk/
http://www.lafargeplasterboard.co.uk/wps/portal/FireProtection

[Paul2886]

Might offer some help:

http://www.jcc-lighting.co.uk/fireguard_ceiling_testing

[nearlythere]

Useful stuff thanks. What I have is an enquiry from a client where BC have asked for a certificate to say that 12.5 skimmed plasterboard on a ceiling will provide 1/2hr FR. Never heard of this certification before but the BC person is adamant.
I can remember FS written advice that 12.5mm skimmed will be adequate but this certification bit now seems to be an issue. I know someone in BC in another area and he can't understand why this is being asked for.

[SeaBass]

All the guidance indicates that if installed correctly, 12.5mm plaster board with a plaster skim will achieve 30 minutes FR. However, like all of these build on site systems the true FR properties will be governed by the standard of installation, the type of plaster board used, the type of fixings used, spacing's of fixings, size of gaps between sheets, the jointing method adopted etc. Therefore, I would imagine that The BCO is looking for an installers certificate stating that the ceiling was installed to a specific standard and in accordance with the manufacturers guidelines. I've known, BCOs ask for similar documentation in relation to wall panelling.

[kurnal]

I would guess that all the BCO is asking for is a copy of the test certificate available from the plasterboard manufacturer to show that the particular plasterboard used in that particular configuration has been subject to a BS476 test.

Products and configurations that have successfully passed the test are usually then published by the manufacturers eg in the white book or in the old days the Cape Boards handbook for example. A call or email  to the board manaufacturer should be all that is needed to get the certificate.

[nearlythere]

Thanks all. Will try.

[kurnal]

NT

You need a copy of the BRE digest 208 - increasing the fire resistance of timber floors.

Increasing the fire resistance of existing timber floors-  ISBN0851253598

Gives general guidance and simple examples on increasing fire resistance for periods of up to one hour by adding protection to the underside of ceilings, over the floor boarding and between the joists. 8 pages.

If you can show compliance with this, the BCO should accept it.

pm me if you need further info.

[kurnal]

BR128 may also be of interest.

[Fishy]

You won't get 30 minutes fire resistance (integrity) from a single layer of 12.5mm thick standard plasterboard on a ceiling. 15-20 mins at most. You can get 'modified' 30 minutes F/R from a timber joisted floor with 21mm softwood floorboards (see the Gyproc 'White Book' - http://www.british-gypsum.com/pdf/WB09_WHITE_BOOK_08.pdf), but bear in mind that the 30 minutes applies to Loadbearing Capacity only - not integrity or insulation, so it's not providing a fire separating function for the full 30 mins.  'Modified' fire resistance only applies to dwelling houses, though.

One layer of 12.5mm Gyproc with appropriately sized joists and min 21mm tongue & groove softwood floorboards will give you 30 minutes F/R.  If you need 30 minutes from the plasterboard alone, you'll need at least two layers of plasterboard, or use a plasterboard with enhanced fire resistance (e.g. Fireline), with appropriate insulation above.  You'd also need to put noggins between the joists to support the board edges.