Any ideas or use for ISO foam board?

If it has properties similar to the pink or blue expanded polystyrene foam (sanding/cutting/carving/grating/shaping, etc.), then I don't know why it couldn't or shouldn't be usable as sub-roadbed or scenery land form usage.

And, if you have a bunch of it lying around doing nothing, then the price is definitely right!

Paul.

The "Stuff",  pun intended, is great! 

Just realize that it is a lethal smoke hazard in case of fire.  BOCA requires that any residential  ISO foam be covered by a minimum of 1/2"  of drywall to allow evacuation of a residence in case of fire. 

It is forbidden in local retirement homes due in part to the delay factor in case of emergency evacuation.

We used it regularly in home renovation because of it's R factor.  It also makes great attic boxes to cover  the frame of pull down steps.  

Just be careful, it's smoke can be a killer.

For use in model RRing always stack it with adhesive like layer cakes, do not use it on an angle for embankments.  We had issues with it deforming.  I like to brush a thick gypson slurry over it for some kind of encasement.  After losing everything in a house fire I am really hung up on codes.

It is real easy to get a clean cut with a 6" spackle knife.

Just lightly drag the knife along a cut line to establish an indention. The repeat the stroke with increasing force until you find the sweet spot of an angle of attack.  You can cut wide radius curves and of course straight lines  easily.  If you develop little crumbs, STOP.  You do not have the correct angle.  Restart and you will soon see how easy this is. 

Note below how the blade by the 5th or 6th pass is thru 2" of foam.

Below is an unretouched photo  of how clean the cut can be.

In my free standing train room I used a combination of a 2" sheet and a 1 1/2" sheet for the 3 1/2" bays.  As you see the fit can be snug and clean.  The scrap can be patched in every so many bays because it cuts so clean.

Tom Tee posted:

The "Stuff",  pun intended, is great! 

Just realize that it is a lethal smoke hazard in case of fire.  BOCA requires that any residential  ISO foam be covered by a minimum of 1/2"  of drywall to allow evacuation of a residence in case of fire. 

It is forbidden in local retirement homes due in part to the delay factor in case of emergency evacuation.

We used it regularly in home renovation because of it's R factor.  It also makes great attic boxes to cover  the frame of pull down steps.  

Just be careful, it's smoke can be a killer.

For use in model RRing always stack it with adhesive like layer cakes, do not use it on an angle for embankments.  We had issues with it deforming.  I like to brush a thick gypson slurry over it for some kind of encasement.  After losing everything in a house fire I am really hung up on codes.

It is real easy to get a clean cut with a 6" spackle knife.

Just lightly drag the knife along a cut line to establish an indention. The repeat the stroke with increasing force until you find the sweet spot of an angle of attack.  You can cut wide radius curves and of course straight lines  easily.  If you develop little crumbs, STOP.  You do not have the correct angle.  Restart and you will soon see how easy this is. 

Note below how the blade by the 5th or 6th pass is thru 2" of foam.

Below is an unretouched photo  of how clean the cut can be.

In my free standing train room I used a combination of a 2" sheet and a 1 1/2" sheet for the 3 1/2" bays.  As you see the fit can be snug and clean.  The scrap can be patched in every so many bays because it cuts so clean.

Tom, thanks so much. That's a lot of food for thought. In the last picture, do you have the poly foam stacked on top of the ISO foam? What is the benefit of using them in tandem?