# Thickness of ply for "cut out" sub-surface



## Sunsanvil (Jan 25, 2017)

Not sure the correct term for it, but what thickness of ply is generally required for this method of supporting track:










Thanks.


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## MichaelE (Mar 7, 2018)

I think 7/16" and 1/2" is about the norm for at least N and HO. TT too.

Your layout is very close to the shape of mine.


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## CTValleyRR (Jul 26, 2014)

I'd agree with Michael. I'd also point out that this method is inefficient and wasteful, but to each his own.


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## D&J Railroad (Oct 4, 2013)

The hard part about this is; after you have your track laid and start your scenery then after a warm humid day you come to your train room and find your road bed looks like a roller coaster. 
I went with 3/4" plywood over my entire empire to avoid having to go back a redo it later on. Compare the price of two sheets of 1/2" plywood vs. one sheet of 3/4" plywood.
Remember, go cheap, be disappointed.


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## Sunsanvil (Jan 25, 2017)

D&J Railroad said:


> The hard part about this is; after you have your track laid and start your scenery then after a warm humid day you come to your train room and find your road bed looks like a roller coaster.


Please tell me more. Do you mean that jigsaw cut plywood like in the photo above is prone to warping? Or is it a lack of full sheet covering the frame?

Thanks.


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## MichaelE (Mar 7, 2018)

If it's not coated with something to seal it, it may absorb moisture from the atmosphere and warp. I would primer it to seal it up.

I have not had any trouble with mine and mine was cut similar to yours. My house is pretty stable as far as humidity is concerned.


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## D&J Railroad (Oct 4, 2013)

Sunsanvil said:


> Please tell me more. Do you mean that jigsaw cut plywood like in the photo above is prone to warping? Or is it a lack of full sheet covering the frame?
> 
> Thanks.


You have no doubt seen plywood that has been left outside, exposed to the weather. It's terribly warped. If your house is climate stable you may not end up with warped plywood. On the other hand, even with sealing it, it can still end up warping then ya have to do the fixes. A lot of times just putting 2x4 under the warped part and using screws to secure it will smooth out those HO scale hills. If takes a little bit of ingenuity to figure out but its not impossible.


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## Sunsanvil (Jan 25, 2017)

Is the issue the narrowness of the plywood strips, or is it that the attachment points are too far apart? A combination of the two?

For a small layout I was thinking of making a frame, cladding the entire thing with 3/8", then doing the cookie cutter think on top of that with frequent blocking to make the grades.


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## Dennis461 (Jan 5, 2018)

Sunsanvil said:


> Is the issue the narrowness of the plywood strips, or is it that the attachment points are too far apart? A combination of the two?
> 
> ....


Yes and yes.
Also bare wood is not good for stability over time. How many furniture pieces do you see in antique shops made of bare wood? 

When I did my room size layout, I used 3/4 inch pine boards splice together rather than cookie cutter. A lot more work, put it was very solid.

If you go ahead with cookie cutter, reinforce the spans with plywood or boards glued under neath between the supports.

And by all means, paint or seal all the wood.


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