Rigid Foam Fire Hazard?

[Hornblower]

Should I be worried about not having any fire retardant on top of my rigid foam layout?  I am thinking about gluing 1 inch pink rigid insulation on top of my 4x8 plywood table to allow me to carve a stream bed and other topographical features, but I have heard that this foam could be a fire hazard.

Please advise,
Hornblower

[Terry Toenges]

This is the same foam they use when building houses right? If it was that much of a fire hazard, I don't know that it would be allowed.

[NarrowMinded]

No more of a fire hazard then all the bits of wood we use for structures, if your really worried get a small piece and take it outside and do a burn test, I know the blue stuff we used at work does not ignite.

NM

[Hornblower]

Owens Corning Pink.  They recommend plaster cloth or thinned plaster painted on. but this will obscure detail of sculpted "rock".

[Hornblower]

Has anybody tried plastering over rigid foam? 

[ChrisS]

straight plaster over the foam wanted to flake off on me.. so i rasped the surface a bit.. and used plaster cloth first.... now you have to rip it off

[lvrr325]

A hot wire foam cutter runs about 415'F; I've stuck a hot soldering iron in it with no issues.  If your foam is burning, the train layout is probably going to be the last thing you're worried about. 

[Jim Banner]

Styrofoam rarely burns in a fire.  But that does not mean it is not a fire hazard.  What it does is break down in the heat, releasing poisonous products.  Up here in Canada, we are required to cover Styrofoam in buildings with at least 1/2" of drywall.  I suppose if your layout framing were metal and there were no combustables in your train room, there would be no problem.  But my train room contains a great deal of wood framing in the layout and has various boxes and cartons stored under it.  So I tend to keep the use of Styrofoam to a minimum.

Where I do use Styrofoam, I like to cover it with plaster.  But not plaster of Paris which quickly breaks down when heated.  Rather, I like all purpose drywall joint cement.  The all purpose variety is approved, in Canada at least, for use with fire resistant drywall.  That means the joint cement itself is also fire resistant.  I convinced myself of this by applying a 1/4" layer to a wood surface and letting it dry for a week.  At the end of the week, I used a high temperature propane torch (one designed for silver brazing, not just soft soldering.)  It quickly turned the surface of the joint cement red, then more slowly to white hot.  After about a quarter of an hour at white heat, I turned off the torch and broke off the joint cement with a hammer.  The surface of the wood was warm, but had not yet started to char.  I am not sure of the exact surface temperature but a piece of Easy-Flo 45 silver solder sitting on the surface melted before the surface reached white heat.  Easy-Flo 45 has a rate melting temperature of about 1100^o F.  I do not know at what temperature Styrofoam breaks down, but I understand temperatures over 1000^o  often occur in fires.  And I deffinitely recommend against anyone extending these tests to Styrofoam or to plaster of Paris.  You might not survive the breakdown products of the Styrofoam and being blasted by white how bits of plaster when it decrepitates in the heat is not much fun either.

The upside of using joint cement is that it can be worked much like plaster of Paris to make various forms of ground.  You cannot apply it as thickly as plaster of Paris (1/4" is already pushing it) and it takes longer to dry.  In compensation, it sticks better to Styrofoam, particularly if you first scarify the surface with a rasp, coarse sand paper, or a piece of old bandsaw blade.

Jim

[HarryHotspur]

Keep in mind that wood burns far more readily than styrofoam, so try not to use any wood on your layout.

[2foot6]

There is probably no more hazard from the foam fumes than the fumes from all the plastics involved on the layout ,including the rolling stock(unless you have brass) It is hard to get foam to burn,but the fumes are bad for you.Precautionary   rules  should apply to any materials used    ie.  regards to naked flames  , placement of soldering iron  etc. Its a matter of understanding the risks and local government rules and applying safety techniques in the way we conduct our hobbies.  Its to wet here in  eastern Australia to burn anything  cheers Peter

[mabloodhound]

I suggest you also do not stay in the room when it is on fire.   The fumes can damage your lungs. 

[tfman]

I suggest you also do not stay in the room when it is on fire.   The fumes can damage your lungs. 

Not to mention The Severe Burns from staying in the room!

[Joe323]

And the emotional trama of seeing your layout go up in flames.

[railsider]

Good idea maybe to have an all-purpose fire extinguisher at hand. Check to make sure it will handle the type of material you use in building your layout.
And be careful, just on general principles.

[DWU]

look around your workbench,now the layout,98% is probably flamable,most of it would go up in flames long before the foam,I wouldnt be too concerned.