Large Scale Central

Foam for outdoor roads?

So I got thinking about Devon’s copying method of foam for buildings. I have a few roads I want/need to build for my layout eventually. Has anyone use a hunk of 1/2" or so foam skimmed with concrete or something else for a road base?

It would be light weight and shapeable (could add sidewalks easy with another layer).

We’ve used concrete patch on the foundation of our buildings with no issue. These are, of course, vertical surfaces, so the comparison may be moot. Also, don’t ask me how this stands up top freezing!


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I’d have a couple concerns with that approach, starting with the degradation of the foam placed on the ground. After the bugs / whatever ate it away (e.g., see related posts on bridges & portals), you’d be left with a thin concrete shell. Even if the foam survived, stepping on it would crush that and the concrete veneer.

Maybe I’m missing the benefit of “light weight”? Are you intending portability? If so, I’d doubt the foam would be rigid enough to extract a road section from the dirt and relocate intact. Then there’s all the curves and intersections which the 2nd locale wouldn’t match.

Consider also the perfectly-even trench that would have to support the foam, to prevent it and its veneer from breaking.

So, why not just concrete, or something similar but stronger? The benefits of that include being able to lay it into an uneven shallow trench, push some mesh in, and smooth out the surface. It would follow the curves and slopes, and permit any type and angle of intersection, all without sawing foam or making perfect trenches.

All you’d need to do is play in the dirt and make some roads! Which can be lots of fun!!

My two cents,

It’s on an elevated benchwork so it wouldn’t be on the ground per say. But yah I guess your right on the bugs. Thats what I steering away from with using foam for a building base.

I was thinking concrete originally but was worried about even more weight on the elevated benchwork.

I’m not anywhere close to doing this road building on the layout yet but it just popped into my head.

Dang, I forgot you were doing an elevated layout, my bad, Craig!

Something Bruce has used a lot for building bases is PVC foamboard. I forget the proper terminology for the product… but he’s done some amazing stuff, scribing the seams of sidewalks and curbs into the material and just painting it.


You could layer it up if you wanted, and glue it with PVC pipe cement I’d expect.

If I could get PVC foamboard here that wasn’t thousands of dollars that might be a workable solution. Shoot, I might as well make it out of styrene. :joy:

Right, all the plastics have gotten stupid expensive…
Whereabouts do you live again, Craig? Just curious.

Cliff, Craig is in always raining Seattle area!
Craig , maybe you could mix up some cement and sand or grout , might be light enough and with some tint you could get a layer to look like old asphalt. Might even be able to work in some potholes along with it.
I have seen them mix dirt and cement here in AZ the make canal banks, it doesn’t have to get concrete wet mixed just damp and then molded into shape you need

I haven’t researched too much about ideas but some sort of light slurry/concrete/cement mixture might be the best. It’s a long ways away still. Need to finish building track and the layout first. Although another building project is starting to call my name. I might have to tell myself spike 18’ of rail, take a break and build one substructure, go back to rail, etc.

A Late friend of mine used that black roofing underlay for his roads on his outdoor bench top layout.
Looks just like asphalt.

I used Foamed PVC (Sintra, Celetex, whatever) BECAUSE it was cheap and easily workable.

I used it for the base of my gas station - just used a pointed instrument to mark lines.

For roads, I used rolled roofing.

I put crushed rock underneath so it was solid enough to walk on, though I suspect that if the ground was smooth there would NOT be ANY problem. (It’s just that THAT would have required MORE work! :grinning_face_with_smiling_eyes:)

I also applied the roofing to look sort of like ballast in Green Springs Yard.

This was applied directly over the treated lumber.

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If I could get my hands on cheap foam PVC, I’d try it for all sorts of stuff. I remember seeing the rolled roofing material for roads before.

I’m not sure how CHEAP you want. :innocent: Poking around, I found a 5 pack of 3 mm 2’ x 3’ at Home Depot for $53.

Not a bad price for something so versatile…Other places (like Tap Plastics) have cut to size.
While 3 mm sounds pretty thin, and it is, it’s also easy enough to cut with a craft knife and straight edge. The 6 mm stuff is a more difficult to cut, but CAN be done. You can also get a 4’x8’ sheet, but it’s awkward to move around and cut. I used to have Tap Plastics cut acrylic to the exact size I wanted. They also deal in styrene.

Having said ALL of that, I used 1/2" PVC for my Bank. I used a tiny jig saw to cut out the windows. Of course PVC was cheaper back then…

Problem is the Home Depots don’t stock it locally. The only place that I was able to find locally was TAP Plastics. TAP Plastics seems to be the only place locally that offers this stuff. I just haven’t made a trip to go get some. I’m kinda on a plastic budget after I went an bought 4x8 sheets of 1/8’ (4), 1/16 (2), and .040 (2). Blew my hobby budget for a while, but I’ll slowly use it up.

I do it all the time and do both bridges and whole structures this way. It is super easy and very clean and has been written up in Garden Railways Magazine.

Get a bucket of Drylock hydraulic cement, something to scoop it with (e.g., big spoon), a spray bottle full of water and a strainer. A cement mixing trough is nice to work in.

Make your structure from foam/styrofoam. Use the spoon to scoop some cement into the strainer. Close the bucket each time to avoid contaminating the dry cement in th bucket with moisture. It will absorb moisture and get hard over time if you don’t, and you certainly don’t want any overspray going in there.

Shake/tap the strainer over your structure to make an even layer.

Mist is with the spray bottle until saturated.

Repeat until you’ve built up ~1/4" on the foam.

Rotate the foam and do the next side.

You can control the final texture. Lots of spray at the end and you get a smooth texture.

Spray then sprinkle a final coat of cement gives a “stucco” texture.

Todd, when doing a side , do you let it dry for a bit before adding and spraying the next layer, or just sprinkle , wet then sprinkle again until you get the buildup you are looking for? Thanks for the info!

Craig, FWIW, the Komatex product Bruce was describing is also available at your Lander store for $53. When I put in a Seattle zip code of 98101, it offers free ship to store or home. Maybe it’ll be a free ship to wherever you are as well.

They always say it’s available in the store but when you show up it’s not there. I’ll try again later this week when I’m close to a HD to see if they have anything.

Sprinkle, wet, sprinkle, wet until that side is done then move on. You don’t wait for anything to dry until you are done or need to handle it from the side you just worked on.

Once you start doing it, you get the hang of it very quickl, and if the piece is angled, you can even do two sides at a time.

BTW, you can make a metal armature and cover it with tape and sprinkle, wet, sprinkle, wet addin to build up the inside. The nremove the tape and do the outside and you have a hollow rock to put over something. Leave a hole at the top and hide your sprinklers as rocks.

I do these things, and more, with hydraulic cement on my railroad.

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On my end, it wasn’t in stock either, just free to ship to store or your home. I can send a sample to you if you want to see what it’s like to work with.

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