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Foamboard on Plywood
Nigel W asks:
“I have been watching videos on laying foam board, onto the plywood, Please can you let me know why?
Is this better than laying railway tracks straight onto the plywood? I will be setting up a DCC layout soon. If I do lay down foam board onto the 3/4 inch plywood and then lay ‘Woodlands-track bed underlay’ on top, then lay the track; will this be the correct thing to do?”
5 Responses to Foamboard on Plywood
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Ply gives a solid (ish) flat base to the layout, and the foam is thought to add a quietening effect.
The ply also holds screws and other fixtures such as switch motors more securely than foam alone. The foam as a top surface is easily carved with knives and hotwire devices (even mum’s kitchen blow torch if you’re careful).
Foam can affect insulation on electrical connections so often a drinking straw is pushed through the foam to act as a conduit although I have never bothered.
There are two types of foam, beaded or extruded. The extruded is more expensive and harder to get but the better of the two. Beaded foam can be messy in use and cut edges fragile. This is where the blowtorch comes in – a quick whisk over the cut surface or along an edge melts and seals the beads.
And you do not need 3/4 plywood. 3/8 would be just fine. I used 1/4 pegboard for my simple layout – 4′ X4′. Just make sure that the cross bracing is set at 16″ as in building buildings.
The foam board reduces noise and is used for landscaping to carve out rivers and streams.
Foamboard, like the pink/HD or blue/Lowes is very popular for layouts these days. Easy to carve and useful for ? ditches and such. Some even use multiple levels of foam for hills, etc. FYI I built my layout with the pink foam/2″ alone. No plywood. Just 16″ spaced braces. A shelf on a wall. As for traditional layouts, the plywood is good. But IMHO it’s the bracing that is what is important. If you could brace every 12″, the foam alone might be OK. And in fact, you could use multiple foam boards. A 2″ on top of a 2″ would really give you neat scenery, rivers and such. As for quieter – I don’t see a lot of difference. As for nails, I just used caulk to fasten roadbed and track. That also lessens noise. Nails can transmit noise. With proper bracing, 3/4″ plywood is not necessary, thinner will suffice. I like bracing or brackets. Another thing I did that not too many others do – is paint. I paint every surface of board, paint roadbed, paint track, etc. I found that my caulk on a painted surface made it really easy to pry up for corrections.
I have had quite a bit of trouble using 20mm thick foam (the same kind as the stuff used for packaging) on a plywood base. I went for this thickness as I wanted to cut away sections to create docks.
Despite locking in the track with glued ballast, I’ve had a lot of track alignment and warping problems.
I’m in Queensland, Australia – and the problems seemed to occur more in hot weather. In the end I ripped up the foam, laid sheet cork onto the plywood base and pinned the track using track pins. This approach seems to be more stable at the moment.
Notwithstanding, other types of foam board (or a thinner layer) may be more stable, so a bit of trial and error may be in order before using foam across the entire layout. Good luck with it!