# I'm new - Plywood vs Foamboard for model railway



## ausmodeler

I am new to model railroading and am building my first layout; i have made a 8' x 4.5' bench and someone suggested putting foamboard 2" on top of the plywood and someone else recommended building a 1" x 4" frame to sit on top of the plywood and then put the foamboard on top of the frame (the latter for portability); adding a frame to the bench top seems like a lot of extra work for portability of something that may not need to be moved for quite sometime. Suggestions...


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## 89Suburban

I am just getting into this hobby and just put down a 1" foam board on my train table and I like it very much.


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## ausmodeler

*Foamboard on Bench*

Can you see any advantage to building this 1" x 4" frame, putting it on top of the table and then putting the foamboard on top of that? I'm ready to lay track once I decide whether or not to use this frame or just put the foamboard right onto the table.
Also, how did you fasten the foamboard to the table (glue???)
Thanks so much for your input.


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## ausmodeler

89Suburban said:


> I am just getting into this hobby and just put down a 1" foam board on my train table and I like it very much.


Can you see any advantage to building this 1" x 4" frame, putting it on top of the table and then putting the foamboard on top of that? I'm ready to lay track once I decide whether or not to use this frame or just put the foamboard right onto the table.
Also, how did you fasten the foamboard to the table (glue???)
Thanks so much for your input.
ausmodeler is online now Report Post


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## Mark VerMurlen

If I'm reading this right, you've already got a bench/table that has plywood already on top of it. Is that right? If so, you can just lay your track right on the plywood. That's what I did on my first layout. The disadvantage of this is that its hard to "go down" if you want to model some ditches, gullies, rivers, or lakes below the grade of your plywood top. If you put foam down on top of the plywood, its then much easier to carve out the foam to get below the track height. Thicker foam allows you to get deeper depressions into the layout. Most people choose either 1" or 2" thick rigid foam. By the way, if you didn't already have the plywood on top of your bench structure, you could have directly glued the rigid foam to the bench supports. The 2" foam is quite rigid and can support a good amount of weight without any plywood support under it. For glue, use a construction grade adhesive that is foam safe. Most home improvement stores will carry this.

I would definitely NOT put a 1x4 grid structure between the tabletop plywood and the foam. That dead space isn't easily accessible and would be a real pain to deal with when running wire underneath the layout. Maybe this suggestion was made by folks that didn't understand that you already have a bench structure built. Its typical to use 1x4 material to build the bench structure itself.

Mark


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## traction fan

*Upside down?*



ausmodeler said:


> Can you see any advantage to building this 1" x 4" frame, putting it on top of the table and then putting the foamboard on top of that? I'm ready to lay track once I decide whether or not to use this frame or just put the foamboard right onto the table.
> Also, how did you fasten the foamboard to the table (glue???)
> Thanks so much for your input.
> ausmodeler is online now Report Post


 ausmodeler;

The normal construction would be a frame of 1"x3" lumber,(or 1"x4" if you wish but it doesn't need to be that big.) with a crosspiece of 1"x3" about every 16". This is called open grid benchwork, and it is quite strong, fairly rigid, but not very resistant to warping. (I don't know what your humidity is like, where you live.) 
OK so we have this nice frame, we've added four legs to support it, Now what next? That's a mater of individual preference. Some people glue the plywood on top of the frame,(which makes the table even stronger, and more rigid, at the expense of making it heavier.) and then they glue the foam on top of the plywood. (Latex caulk works well for this. If you elect to use glue, make sure it is not solvent based. Solvents will eat through the foam and destroy it. Another good, and safe for foam, "glue" is ordinary latex water-based house paint. If you paint the foam, and plywood with paint it will act like contact cement and hold the sheet of foam, and the sheet of plywood, together firmly.) To glue frame/grid to plywood, use ordinary carpenter's yellow wood glue, or even Elmer's white glue.
I have never even heard of anyone ever attaching plywood, and foam, to OPPOSITE sides of the frame, as you describe. That's downright bizarre! Are you sure that's what you read, or heard? No, there is no advantage to doing that. 
The foam can be carved out to make ditches rivers, etc. that are below track level. If 2" foam is used over the 16" grid I described, the plywood is not necessary; and to save weight, and money, some modelers leave the plywood out of the picture altogether. A 2'" thick piece of extruded foam (Not the much weaker white Styrofoam "beadboard") Will easily support the model railroad, and even the model railroader if you are careful. Plywood does provide a convenient mounting surface for wiring, switch machines, and any other under-the-layout hardware. A good compromise for this "plywood, or not" question is to use 1/4" thick Luan plywood under the foam and on top of the grid frame. It's lighter than conventional plywood, and yet provides the mounting surface.
All of what I just said, and a whole lot more information that might help you, is in the attached pdf files; you might want to look through them and pick out what suits your situation. Welcome aboard, and feel free to ask any questions you like.

Have fun;

Traction Fan:smilie_daumenpos:

View attachment Where do I start (revised version).pdf


View attachment MODEL RAILROADING ON A BUDGET.pdf


View attachment Model Railroad Terminology 2.1.pdf


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## ausmodeler

Mark VerMurlen said:


> If I'm reading this right, you've already got a bench/table that has plywood already on top of it. Is that right? If so, you can just lay your track right on the plywood. That's what I did on my first layout. The disadvantage of this is that its hard to "go down" if you want to model some ditches, gullies, rivers, or lakes below the grade of your plywood top. If you put foam down on top of the plywood, its then much easier to carve out the foam to get below the track height. Thicker foam allows you to get deeper depressions into the layout. Most people choose either 1" or 2" thick rigid foam. By the way, if you didn't already have the plywood on top of your bench structure, you could have directly glued the rigid foam to the bench supports. The 2" foam is quite rigid and can support a good amount of weight without any plywood support under it. For glue, use a construction grade adhesive that is foam safe. Most home improvement stores will carry this.
> 
> I would definitely NOT put a 1x4 grid structure between the tabletop plywood and the foam. That dead space isn't easily accessible and would be a real pain to deal with when running wire underneath the layout. Maybe this suggestion was made by folks that didn't understand that you already have a bench structure built. Its typical to use 1x4 material to build the bench structure itself.
> 
> Mark


Thank you so much for your great, detailed reply; you were a huge help. I am just going to use the foamboard on the plywood; I posted my question because a guy at the model railway store in Sarasota, Fl strongly recommended the 1" x 4" frame on top of the bench in order to have a lightweight layout on top that could easily be moved; it made no sense to me as there would be this 4"+ deadspace between the foamboard and the bench top which I though could be a wiring nightmare. Thanks again - I appreciate it.


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## ausmodeler

traction fan said:


> ausmodeler;
> 
> The normal construction would be a frame of 1"x3" lumber,(or 1"x4" if you wish but it doesn't need to be that big.) with a crosspiece of 1"x3" about every 16". This is called open grid benchwork, and it is quite strong, fairly rigid, but not very resistant to warping. (I don't know what your humidity is like, where you live.)
> OK so we have this nice frame, we've added four legs to support it, Now what next? That's a mater of individual preference. Some people glue the plywood on top of the frame,(which makes the table even stronger, and more rigid, at the expense of making it heavier.) and then they glue the foam on top of the plywood. (Latex caulk works well for this. If you elect to use glue, make sure it is not solvent based. Solvents will eat through the foam and destroy it. Another good, and safe for foam, "glue" is ordinary latex water-based house paint. If you paint the foam, and plywood with paint it will act like contact cement and hold the sheet of foam, and the sheet of plywood, together firmly.) To glue frame/grid to plywood, use ordinary carpenter's yellow wood glue, or even Elmer's white glue.
> I have never even heard of anyone ever attaching plywood, and foam, to OPPOSITE sides of the frame, as you describe. That's downright bizarre! Are you sure that's what you read, or heard? No, there is no advantage to doing that.
> The foam can be carved out to make ditches rivers, etc. that are below track level. If 2" foam is used over the 16" grid I described, the plywood is not necessary; and to save weight, and money, some modelers leave the plywood out of the picture altogether. A 2'" thick piece of extruded foam (Not the much weaker white Styrofoam "beadboard") Will easily support the model railroad, and even the model railroader if you are careful. Plywood does provide a convenient mounting surface for wiring, switch machines, and any other under-the-layout hardware. A good compromise for this "plywood, or not" question is to use 1/4" thick Luan plywood under the foam and on top of the grid frame. It's lighter than conventional plywood, and yet provides the mounting surface.
> All of what I just said, and a whole lot more information that might help you, is in the attached pdf files; you might want to look through them and pick out what suits your situation. Welcome aboard, and feel free to ask any questions you like.
> 
> Have fun;
> 
> Traction Fan:smilie_daumenpos:
> 
> View attachment 399194
> 
> 
> View attachment 399202
> 
> 
> View attachment 399210


Thank you very much for your great and detailed reply; you were a huge help. I posted my question originally because one of the owners at the model railway store in Sarasota, Fl strongly recommended the 1" x 4" frame *on top* of the bench in order to have a lightweight layout on top that could easily be moved should I ever want to move it and then I could dismantle the bench and move it out without disrupting the layout itself; it made no sense to me as there would be this 4"+ dead-space between the foamboard on top of this frame and the bench top which I thought could be a wiring nightmare. Thanks again - I appreciate it. The attachments you sent were also wonderful - Thanks! One last questions; by extruded foam, is that the same as expanded polystyrene (Polyshield)


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## Eilif

ausmodeler said:


> One last questions; by extruded foam, is that the same as expanded polystyrene (Polyshield)


I looked up polyshield and I think it might be different. I'm not sure about the actual material and it appears to have an additional later laminated on top.

The stuff you want is the pink or blue rigid sheets that have no additional layer to impede carving and cutting.


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## Dennis461

Why not just start laying roadbed and track? The foam at this point would only be used for scenery, maybe a hill or two. If you have some framework under the middle of the plywood (not just around the outside), you can cut into it to make lower elevations for scenery without the plywood sagging.

My tiny layout is going to flat desert with a gorge, and it's all wood.


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## ausmodeler

Since I already have Polyshield (the compressed beaded foamboard), do you see any problem with using it and just putting a 1" layer of the blue or pink foamboard on top of it or should I just throw out the Polyshield and start all over with the pink or blue board? Also the 2" blue or pink board is not even available within 100 miles of where I am located. Also, is there any problem cutting the pink or blue foamboard in 1/2 just to get it into my vehicle and then glueing it back together on the bench top to make a 4' x 8' sheet again.


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## ausmodeler

Eilif said:


> I looked up polyshield and I think it might be different. I'm not sure about the actual material and it appears to have an additional later laminated on top.
> 
> The stuff you want is the pink or blue rigid sheets that have no additional layer to impede carving and cutting.


Since I already have Polyshield (the compressed beaded foamboard), do you see any problem with using it and just putting a 1" layer of the blue or pink foamboard on top of it or should I just throw out the Polyshield and start all over with the pink or blue board? Also the 2" blue or pink board is not even available within 100 miles of where I am located. Also, is there any problem cutting the pink or blue foamboard in 1/2 just to get it into my vehicle and then glueing it back together on the bench top to make a 4' x 8' sheet again.


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## ausmodeler

traction fan said:


> ausmodeler;
> 
> The normal construction would be a frame of 1"x3" lumber,(or 1"x4" if you wish but it doesn't need to be that big.) with a crosspiece of 1"x3" about every 16". This is called open grid benchwork, and it is quite strong, fairly rigid, but not very resistant to warping. (I don't know what your humidity is like, where you live.)
> OK so we have this nice frame, we've added four legs to support it, Now what next? That's a mater of individual preference. Some people glue the plywood on top of the frame,(which makes the table even stronger, and more rigid, at the expense of making it heavier.) and then they glue the foam on top of the plywood. (Latex caulk works well for this. If you elect to use glue, make sure it is not solvent based. Solvents will eat through the foam and destroy it. Another good, and safe for foam, "glue" is ordinary latex water-based house paint. If you paint the foam, and plywood with paint it will act like contact cement and hold the sheet of foam, and the sheet of plywood, together firmly.) To glue frame/grid to plywood, use ordinary carpenter's yellow wood glue, or even Elmer's white glue.
> I have never even heard of anyone ever attaching plywood, and foam, to OPPOSITE sides of the frame, as you describe. That's downright bizarre! Are you sure that's what you read, or heard? No, there is no advantage to doing that.
> The foam can be carved out to make ditches rivers, etc. that are below track level. If 2" foam is used over the 16" grid I described, the plywood is not necessary; and to save weight, and money, some modelers leave the plywood out of the picture altogether. A 2'" thick piece of extruded foam (Not the much weaker white Styrofoam "beadboard") Will easily support the model railroad, and even the model railroader if you are careful. Plywood does provide a convenient mounting surface for wiring, switch machines, and any other under-the-layout hardware. A good compromise for this "plywood, or not" question is to use 1/4" thick Luan plywood under the foam and on top of the grid frame. It's lighter than conventional plywood, and yet provides the mounting surface.
> All of what I just said, and a whole lot more information that might help you, is in the attached pdf files; you might want to look through them and pick out what suits your situation. Welcome aboard, and feel free to ask any questions you like.
> 
> Have fun;
> 
> Traction Fan:smilie_daumenpos:
> 
> View attachment 399194
> 
> 
> View attachment 399202
> 
> 
> View attachment 399210


Since I already have Polyshield (the compressed beaded foamboard), do you see any problem with using it and just putting a 1" layer of the blue or pink foamboard on top of it or should I just throw out the Polyshield and start all over with the pink or blue board? Also the 2" blue or pink board is not even available within 100 miles of where I am located. Also, is there any problem cutting the pink or blue foamboard in 1/2 just to get it into my vehicle and then glueing it back together on the bench top to make a 4' x 8' sheet again.


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## CTValleyRR

Eilif said:


> The stuff you want is the pink or blue rigid sheets that have no additional layer to impede carving and cutting.


Or adhesive sticking to it...


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## Eilif

ausmodeler said:


> Since I already have Polyshield (the compressed beaded foamboard), do you see any problem with using it and just putting a 1" layer of the blue or pink foamboard on top of it or should I just throw out the Polyshield and start all over with the pink or blue board? Also the 2" blue or pink board is not even available within 100 miles of where I am located. Also, is there any problem cutting the pink or blue foamboard in 1/2 just to get it into my vehicle and then glueing it back together on the bench top to make a 4' x 8' sheet again.


Several different isses here.

1) Regarding beaded polystyrene foam. It is a mess to work with when using knifes and such. On the other hand it's easy to cut neatly with a foam cutter, and usually (though I don't know about polyshield) makes alot less fumes with a hot foam cutter than the pink and blue material. If you are planning to cover the surface with plaster cloths or somesuch then the "beaded" nature of the foam isn't an issue. All this to say there may be better options, but it is a good enough material. Consider that Woodland scenics bases their entire scenery system around it. 

2)As to layering, if you've already got a plywood base, I'd probably just go with one kind of foam or the other. The exception would be if you want to make some really deep valleys then if you have to buy more foam, buy the pink or blue stuff.

3) For transportation of pink or blue foam there's nothign wrong with cutting and reassembling. After scoring it tends to snap-break quite evenly. Beaded foam can be cut also does not score and break neatly.

4) If you're still going back and forth about whether to use any foam or not, I'd say that if you are only going to have one drop ( like a river or ravine) then maybe just stick with plywood and do some cutouts. However, if you like the idea of being able to easily add diches, small ravines, creeks, turntables cuverts and gentle undulations that go lower than the level of your track base then foam is a great idea that will pay dividends down the road.

Since you've already got the polyshield (is it the raw foam or foam with additional material laminated too it) I'd say that if you have (or are willing to purchase a foam cutter) than maybe just use that. If you don't have or want to buy a foam cutter I'd advise tossing the polyshield and getting some pink or blue foam.

One other thing I'd suggest is that if you decide to buy more foam of any type checking craigslist to see if anyone has some surplus foam to sell. To start my layout I bought a bunch of sheets (most of them intact) equaling about 8x4x1 for $30.


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## ausmodeler

Eilif,
Do you know if it is OK to cut the blue or pink foamboard and then just glue it tightly back together on the plywood top of the train table - I can't get a 4' x 8' in my car without cutting it. Also, since my table top is 4'6" x 8" I would need to add that 6" piece along the back anyway.


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## ausmodeler

Eilif said:


> Several different isses here.
> 
> 1) Regarding beaded polystyrene foam. It is a mess to work with when using knifes and such. On the other hand it's easy to cut neatly with a foam cutter, and usually (though I don't know about polyshield) makes alot less fumes with a hot foam cutter than the pink and blue material. If you are planning to cover the surface with plaster cloths or somesuch then the "beaded" nature of the foam isn't an issue. All this to say there may be better options, but it is a good enough material. Consider that Woodland scenics bases their entire scenery system around it.
> 
> 2)As to layering, if you've already got a plywood base, I'd probably just go with one kind of foam or the other. The exception would be if you want to make some really deep valleys then if you have to buy more foam, buy the pink or blue stuff.
> 
> 3) For transportation of pink or blue foam there's nothign wrong with cutting and reassembling. After scoring it tends to snap-break quite evenly. Beaded foam can be cut also does not score and break neatly.
> 
> 4) If you're still going back and forth about whether to use any foam or not, I'd say that if you are only going to have one drop ( like a river or ravine) then maybe just stick with plywood and do some cutouts. However, if you like the idea of being able to easily add diches, small ravines, creeks, turntables cuverts and gentle undulations that go lower than the level of your track base then foam is a great idea that will pay dividends down the road.
> 
> Since you've already got the polyshield (is it the raw foam or foam with additional material laminated too it) I'd say that if you have (or are willing to purchase a foam cutter) than maybe just use that. If you don't have or want to buy a foam cutter I'd advise tossing the polyshield and getting some pink or blue foam.
> 
> One other thing I'd suggest is that if you decide to buy more foam of any type checking craigslist to see if anyone has some surplus foam to sell. To start my layout I bought a bunch of sheets (most of them intact) equaling about 8x4x1 for $30.


Eilif,
Thank you so much for you detailed feedback on the foam - I really appreciate it. My foamboad has what looks like a thin silver (metal) foil layer along the bottom of the foam.


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## Eilif

ausmodeler said:


> Eilif,
> Thank you so much for you detailed feedback on the foam - I really appreciate it. My foamboad has what looks like a thin silver (metal) foil layer along the bottom of the foam.


You're very welcome.
Full disclosure, I'm fairly new to model railroading, but I've been using various types of foam in the construction of wargaming scenery for some time.

As for the metal layer, you can probably glue the metal layer right to the tabletop, but if there's metal on the top layer you're going to want to peel that away. If it's not too late to swap the polyshield (which I believe is "Expanded" polystyrene foam) for some unfaced pink or blue "extruded" foam board I'd do that.



ausmodeler said:


> Eilif,
> Do you know if it is OK to cut the blue or pink foamboard and then just glue it tightly back together on the plywood top of the train table - I can't get a 4' x 8' in my car without cutting it. Also, since my table top is 4'6" x 8" I would need to add that 6" piece along the back anyway.


Perfetctly OK. I brought mine home in big sheets but I still had to chop it up downstairs to make the two dual-layer 4x5 foot panels that I carried up to the attic and placed on top of the vintage homebuilt (not by me) 9x5 pingpoing table. You can see pictures what I mean in the topic I linked to previously.

I'm going to glue down the edges to the table and smooth over the top of the join, but I'm deliberately building it in such a way that if necessary I can relatively easily cut it in two and transport the two 4x5 halves out of my attic relatively intact. This would allow me to sell or give away the layout if I decide to completely rebuild the layout someday, sell the house, exit the hobby, etc.


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## traction fan

*Expanded polystyrene?*



ausmodeler said:


> Thank you very much for your great and detailed reply; you were a huge help. I posted my question originally because one of the owners at the model railway store in Sarasota, Fl strongly recommended the 1" x 4" frame *on top* of the bench in order to have a lightweight layout on top that could easily be moved should I ever want to move it and then I could dismantle the bench and move it out without disrupting the layout itself; it made no sense to me as there would be this 4"+ dead-space between the foamboard on top of this frame and the bench top which I thought could be a wiring nightmare. Thanks again - I appreciate it. The attachments you sent were also wonderful - Thanks! One last questions; by extruded foam, is that the same as expanded polystyrene (Polyshield)


ausmodeler;

I'm not entirely certain about what "expanded polystyrene" or "polyshield" are, but I suspect that the former is the white stuff more commonly known by its trade name: "Styrofoam"; and the latter is just the same old Styrofoam with a sheet of aluminum foil coating one side. If so, it's not a particularly good layout base, or scenery material. It's very weak structurally. You will definitely need at least a 1/4" thick sheet of Luan plywood, or a 1/2" thick sheet of regular plywood, between the foam and the wood frame/grid, for support. Without the plywood, you could easily put your hand right through white Styrofoam beadboard. Styrofoam beadboard is incredibly messy when cut. Clouds of its beads blow all over the place, stick to you, your clothes, and everything else in sight; and are very difficult to round up. A broom just puts them in motion again. A shop Vacuum is the best way.
Still, it is possible to use it, though the extruded foam is much better. The good foam is not white, but pink, blue, or green, depending on the brand. It is much, much, stronger; and more rigid, and less messy,though it does produce plenty of dust when cut with a saw. The clean way of cutting either type of foam is with either a hot wire foam cutter, or an electric hot knife. These tools don't produce dust or beads, but they do produce some strong, nasty smelling, fumes; so have plenty of fresh air ventilation if you use either tool. Hot wire foam cutters can be expensive. You can order one from www.micromark.com 
An electric hot knife will do the same job although it makes a wider cut and is not as neat. They are much cheaper. You can order the knife at www.harborfreighttools.com Unless you want to borrow Crocodile Dundee's enormous knife! :laugh:

You mentioned Sarasota, Florida. Is that where you live, and where you will be building your model railroad? I had assumed you were in Australia. If you are building a layout in Florida, there is an additional point to consider, humidity! Because of the very high humidity there, the wood of your layout will warp unless you take special precautions. First, don't use conventional flat 1"x4" planks. They will definitely warp if exposed to the swamp-like humidity of Florida. Instead, use two smaller planks screwed, and glued, together in an 'L' shape. Just about any combination of 1"x3" or 1"x2' planks will work fine, and will be a lot lighter, and a little cheaper than two 1"x4" planks assembled into a massive , heavy, beam. Model railroaders often call this "L-girder." Once made, it is highly resistant to warping, in fact, you couldn't bend it if you tried to. Do this with the legs, the outer frame, and the cross pieces. (Called "Stringers," or "Joists" ) Use the yellow water-resistant carpenter's glue. 

The other precaution is to paint all the wood to help seal out moisture.The combination of L-girder, and paint sealing, will virtually eliminate warping.

If you are in Florida, you may not be able to find the pink, blue, or green, extruded foam in any local stores. I have that same situation where I live in San Diego, California. Extruded foam is made as home insulation. The makers, and marketers, of extruded foam, for reasons surpassing understanding, don't realize that insulation is needed to keep air-conditioned cool air in and scorching heat out; just as much as it is to keep furnace heat in, and freezing cold weather out. Therefore, in their infinite wisdom, they don't sell it in warm climates. (like southern California, and, I'm guessing, Florida.) If that is true then you may have to settle for the inferior white, "expanded polystyrene",because that's all you can get. The aluminum foil coating of "polyshield" is useless for model railroad purposes, and pushes the price up, so I would just use the plain white Styrofoam, if you can't get extruded foam there. If you already have "polyshield", it is possible to peal the aluminum foil off.

The photos below show one section of my layout. The second photo shows the bottom view with small L-girder framework and all the wood painted. 

















Hope that helps clear up the foam question;

Traction Fan:smilie_daumenpos:


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## 89Suburban

I did not glue my board to the table I am still in beta testing for the layout I want. You should be able to find extruded foam at any concrete construction supply house that caters specifically to the concrete contractor. Contractors use it under slabs, especially freezer slabs, and foundation walls. It is 25 - 40 psi rated.

The white bead board is expanded polystyrene and makes a mess and is not as strong.


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## Gwent Rail

Styrofoam? (aka Expanded polystyrene) - used it and lived to regret it! 
Messy and does not take pins at all well.
The only way I stopped it "doing my head in" was to paint the whole thing (twice) and then paint every cut / gouge I made. I gave up in the end and ripped it all up.
Then I saw it's advantage, anything not heavily glued to it rips apart sooooo easily. 

Extruded foam is a different matter - that's the pink or blue stuff being discussed above.
Very good, stable and cuts well. You'll see the difference the first time you cut it and don't leave a huge mess that sticks electrostatically to everything.


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