A Railroad with Relevance

Foam Education

Written By: Alan - Nov• 11•13

I used up the two sheets of insulation foam I bought to start the landforming. While cutting and fitting the pieces it occurred to me that 2′ x 8′ panels would be easier to work with than 4′ x 8′ panels since most of the pieces I am cutting are long and narrow. Since I had to get more foam I decided to see if 16″ or 2′ wide panels are available. It turns out that both Owens Corning and Dow make narrower panels but unfortunately the local Home Depot, Lowes, and Menards don’t stock them. I am bound to 4′ x 8′ sheets.

My search for the alternate size panel enlightened me to the various grades of insulation foam. Turns out the manufacturers make several different grades of foam that differ in one key aspect – their compressive strength. It makes sense when you look at the intended applications for each. Low strength for cavity insulation in walls, medium strength for foundation insulation, and high stregth for heavy traffic applications. Who’d a thought it?

Take Foamular for instance. It is the Owens Corning product I am using for a scenery base. It comes in 5 different versions – Foamular 150, 250, 400, 600, 1000. The number part of the product name designates its compressive strength – 150 means 15lb./in², 250 means 25lb./in², 400 means 40lb./in², and so on. Dang, wish I had known this in the beginning. I bought 150 initially because it was the only 2″ my local Home Depot had on hand. Now I wish I had checked out Menards and gotten 250. Almost double the compressive strength for only $2 more per sheet. The home improvement stores don’t stock 400-1000 in 2″ sheets and likely they would be too expensive anyway. The compressive strength shouldn’t matter for scenery purposes but with my clumsiness I am likely to rest an elbow on it or drop a tool of some sort. That little extra bit of compressive strength might save the day when I do something stupid. Oh well, live and learn. The rest of the layout will be 250.

Foamular 150 data sheet
Foamular 250 data sheet
Foamular 400, 600, 1000 data sheet

Owens Corning and Dow equivalents data



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  1. Phil Hilton says:

    I’ve never seen a board of foam insulation that wasn’t scored lengthwise, to easily turn a 4×8 sheet into 2 2×8 sheets. or 4 1×8 strips. Even if you find one that isn’t somehow, it’s really simple to score it yourself.

  2. alan says:

    Hey Phil,

    Yeah I found that out. These sheets are scored on 16″ and 24″ centers. I am snapping to long narrow sheets now before I lay in place and mark. Learn something new everyday!

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