Are polystyrene slabs a fire hazard?

[Guest RichardNev]

a couple of years ago i insulated my loft roof rafters with polystyrene slabs, puchased from wickes.These are only in the pitched area of the roof ie the highest point.My worry is that these may be a fire hazard. can you advise please.

thanks. Richard

[Tom Sutton]

From Wikipedia, the free encyclopaedia

Like other organic compounds, polystyrene is flammable. Polystyrene is classified according to DIN4102 as a "B3" product, meaning highly flammable or "Easily Ignited." As a consequence, although it is an efficient insulator at low temperatures, its use is prohibited in any exposed installations in building construction if the material is not flame-retardant. It must be concealed behind drywall, sheet metal, or concrete. Foamed polystyrene plastic materials have been accidentally ignited and caused huge fires and losses, for example at the Düsseldorf International Airport, the Channel tunnel (where polystyrene was inside a railcar that caught fire), and the Browns Ferry Nuclear Power Plant (where fire breached a fire retardant and reached the foamed plastic underneath, inside a fire stop that had not been tested and certified in accordance with the final installation).

I have seen how polystyrene ceiling tiles behave in fire and its not good but these slabs may have been treated so I would contact Wickes and find out, how they should be used and what precautions should you have taken when using them.

[Guest Ray Stewart]

Polystyrene tiles and roles are now produced with a fire retardant additive and have been tested by the Home Office and Fire Safety Agencies and are deemed safe and not a fire hazard.

But they must put up using the correct adhesive (wall paper paste is suitable) and the whole tile or whole sheet must be covered with the adhesive (do not just use the old 5 spots method) so that the complete surface is stuck to the ceiling.

Also the tiles must not be painted with gloss paint which will cause them to be flammable, they should only be painted with emulsion or fire retardant paint.

So, the "new" (this has been the case for several years) style polystyrene tiles are SAFE.

[green-foam]

Polystyrene tiles and roles .

The way I read it, he has neither, he has polystyrene insulation boards.

a couple of years ago i insulated my loft roof rafters with polystyrene slabs

I guess he took Tom's advice. The website says nothing about their flammability or not.

[Guest Bob. E]

I have a utility room which has a flat concrete roof /ceiling which tends to condensate easily so traditional finishes like plaster are not very suitable, as the ceiling will still suffer from condensation problems unless the ceiling is lowered and insulation fitted behind it.  For this reason I am thinking of covering it with modern fire retardant polystyrene tiles.  However, I note the comment from Mr Ray Stewart that these tiles have to be stuck with the correct adhesive and the back of the tiles have to be completely covered with adhesive.  According to sellers of this product Decorators Caulk / sealant can be used to stick the tiles effectively.  Does anyone know if this Is this true, and is OK to apply the caulk /sealant in lines across the back of the tiles, or does it have to be spread in a layer across the whole surface?

[green-foam]

You would have to try one yourself to see if it the brand of adhesive you choose is suitable.

The adhesive should be spread all over (Like you would butter bread) the reason is so you do not trap air above the tile, as you would if you followed the old "4 corner and one middle" dobs method.

[Tom Sutton]

Expanded Polystyrene (EPS) is a good example of how a material with good thermal insulation properties can also have drawbacks.

Firefighters hate polystyrene ceiling tiles because in house fires they melt and drip blobs of burning plastic, and also give off carcinogenic fumes. Many chartered surveyors advise their removal. And yet, even now, there is an apparent resurgence in the fashion for lining walls with thin sheets of the stuff, albeit in versions advertised as “flame retardant”.

Only expanded polystyrene tile adhesives should be used since the Home Office recommends an all-over spread adhesive; these are readily available under different trade names from the same outlets as the tiles. Always check the instructions on the pack to make sure your ceiling surface is suitable for the adhesive. Don’t use an adhesive with a solvent base such as cellulose, which would dissolve the tiles and make them highly inflammable.

I would not advise but if you choose to use them, how they were fixed to the ceiling, is most important and you should spread in a layer across the whole surface of the tile with the adhesive, no spaces, no matter how small. Also on no account should they be painted over with gloss paint which was the major concern, use water based paint or fire retardant paint.

[Guest Graham]

Just wanted to counter Rays statement they are SAFE.  They are not, in fact no combustible material is completely safe. I work for a major insurer as a commercial property underwriter and I can tell you right now, if my loss control surveyors identify EPS panels are used at all in the construction materials they class the fire hazard as adverse, I wouldn't touch the risk with a barge pole and if I were some how compelled to write it, it would be on increased terms I.e. Much higher premium and with large fire excesses. 

If EPS comes into contact with naked flames it will catch fire and it will spread rapidly, treat it all you want, that only offers a delay in combustibility, go with mineral wools or a more modern PIR (Polyisocyanurate) material.  these are still both combustible but are much more fire retardant than EPS at least giving you longer to escape an established fire.