Eggbox wall construction

[kurnal]

Have been in a 1950s school today, the wall construction - even those protecting the staircases of a 4 storey block- were of eggbox construction. A sheet of 12.5mm plasterboard each side of an inner core comprising a cardboard matrix about 40mm square matrix.  The panels appear to be butted up to each other without any framing material and all board edges are visible- ie not taped or filled. The cardboard ignites very easily indeed. It was exposed in many areas where the plasterboard lining has been damaged, especially round door frames.


Reference to the Clasp info website indicates it was common in early CLASP construction and sometimes called paramount partitioning

http://www.scapebuild.co.uk/getattachment/Consult/Services/CLASP-Buildings/Building-Systems/ID_Guide.pdf.aspx

But it does not indicate fire test data.

Has anybody any historic data on the likely fire performance  of this type of construction?  

[SamFIRT]

From experience I can tell you it burns very well indeed. 

I have attended several fires in CLASP construction buildings that have used this interior wall method. Fire rips through the partitions and spreads through the voids endemic in CLSP buildings to take out a building in very little time.

In the past Firefighters would have been committed into the building to create fire breaks and water walls sacrificing part of the building to save other sections; but these days a non-life-risk fire would probably be fought defensively and the property burn to the ground very quickly.

[kurnal]

Yes thanks Sam like you I have attended a number of total loss fres in CLASP buildings and the unseparated and undivided voids above ceilings, the unstopped cavities between curtain walling and inner linings, the absence of any proper compartmentation, the extensive use of glazed screens without any proper support for the glass etc etc are all factors.

I am nervous about the eggbox construction especally where the plasterboard has been damaged on the risk side but can imagine that its fire performance, where it is in in good condition, it may be better than traditional lath and plaster for example. Have chased a few fires in lath and plaster walls as well!

Where it is damaged I also am trying to suggest ways of repairing it, previous practice has been to put gaffer tape over the holes followed by a permanent repair using 6mm plywood! Clearly plasterboard is the answer but patching is not because theres nothing to fix the patch to.

There must have been some tests done on these partitions, I believe it all predates the BB series which I believe set out the first fire safety standards in the design of the schools.

[Tom Sutton]

I believe it all predates the BB series which I believe set out the first fire safety standards in the design of the schools.

Agreed Kurnal, in the early 50's we built most internal walls using brick, breeze and thermalite but towards the end of the 50's these panel walls started to appear. Usually fitted in steel framing the first I remember was stramit panels, some others were made out of wood wool and plaster or plaster board construction with a common problem once the surface was broken you had a tinder box. Incidental they were used in all sorts of building not only CLASP.

As BB7 made an appearance in 1976 then it was after the introduction of this panel walling. http://www.education.gov.uk/schools/adminandfinance/schoolscapital/buildingsanddesign/environmental/a0010942/fire-safety-in-new-and-existing-school-buildings

[Fishy]

The trouble with unframed panelling systems, as opposed to those that are constructed around a structural frame, is that they rely upon the skins to give the wall its strength and stability.  If you lose one skin, or the core itself, or even if you just lose the bond between the skin and the core, the wall loses most of its structural properties and could collapse. This will happen at relatively low temperatures, depending upon the nature of the skins, core and adhesives.  Therefore, you are likely to get much less fire resistance from this type of construction than ‘traditional’ framed constructions that use the same number and thickness of plasterboard layers.  If there are any holes/gaps in the facings, then this is likely to have a dramatic effect on fire resistance, because it will expose the non-fire resisting core directly to the fire.

The other big ‘fire’ issue with this type of construction is cavity barriers (or lack thereof) – if fire does get into the core it will be likely to spread throughout the entire construction unless the appropriate cavity barriers have been installed.  This really needs to be checked, I’d suggest.

At the end of the day, safest to assume that the construction will offer little or no fire resistance, & assess the risk accordingly.

[Davo]

Hi Alan

Will the walls stand coating or lining?

Are you doing life safety or the full Monty?


davo

[kurnal]

Just life safety Davo.

I did the full monty last night but she wasnt impressed.

Its a matter of doing as little as possible and spending as little as possible to make the building safe for its remaining few years life. The place is also full of asbestos so doing anything is expensive.

[William 29]

Kurnal,

I take it this is a means of escape issue and would affect life safety and not just property protection??  What I'm getting at is even if you did have a fire in the staircase walls (and  assuming there are likely ignition sources) could they turn away and use an alternative M of E?  If so I would raise my concerns and detail them as you have described but place more emphasis on the property protection.  From what you describe to make an attempt at providing protected routes to any current standard would be cost prohibitive and given it’s a school I would say would be very unlikely to be actioned.  What standard of AFD do they have?  Would they get sufficient warning to safety evacuate before conditions became untenable?

[kurnal]

Yes that was my final recommendation William, to repair the holes in the partitions to as good a standard as possible using full sheets to ensure fixings are secure and to upgrade the existing L4 to L2 with detection in all rooms adjoining the escape routes and in the unoccupied storerooms and offices.
 

[kurnal]

I believe it all predates the BB series which I believe set out the first fire safety standards in the design of the schools.

Agreed Kurnal, in the early 50's we built most internal walls using brick, breeze and thermalite but towards the end of the 50's these panel walls started to appear. Usually fitted in steel framing the first I remember was stramit panels, some others were made out of wood wool and plaster or plaster board construction with a common problem once the surface was broken you had a tinder box. Incidental they were used in all sorts of building not only CLASP.

As BB7 made an appearance in 1976 then it was after the introduction of this panel walling. http://www.education.gov.uk/schools/adminandfinance/schoolscapital/buildingsanddesign/environmental/a0010942/fire-safety-in-new-and-existing-school-buildings

Thanks Thomas once again I have learned something new every day.
That requirement of the Education (School Premises) Regulations is a new one on me - heres what it says:

Health, safety and welfare
17.—(1) Every part of a school building and of the land provided for a school shall, having regard in particular to the matters mentioned in paragraph (2), be such that the safe escape of the occupants in case of fire is reasonably assured.

(2) The matters referred to in paragraph (1) are—

(a)the likely rate at which flames would spread across exposed surfaces; .
(b)resistance to fire of the structures and of the materials of which the structures are made and their other properties; and .
(c)the means of escape in case of fire. .
(3) Every part of a school building and of the land provided for a school shall be such that the health, safety and welfare of the occupants in aspects other than those referred to in paragraph (1) are reasonably assured.

The notes cite BB7 or BB100 as being the benchmark guidance for existing schools. Theres a thing.

Anyone know why this was not  rescinded by the Fire Safety Order?