I’ve heard to use anthing from 3/8’s all the way up to 3/4 inch plywood… I’d love to be able to use 3/8" due to it’s low cost, and since I’ll be laying at least a couple sheets of foam on top, would that be strong enough to support the weight of the layout? L-girder construction, joists are approximately 12-16 inch spacing depending on where they are on the layout. I do hear that 1/2 inch or thicker would be ideal, but this is a large layout that will require at least 7-10 sheets of plywood, and I’m trying to keep costs down as much as possible.
With two sheets of foam on top, you should be able to get away with 3/8" plywood, but without the foam you would definitely need at least 1/2" thickness.
I should probably mention that around here it’s really hard to find the standard 2" foam sheets that most people use. I’ll only be using probably two or three 1/2" sheets (which is what’s primarily available) glued down to each other and the plywood tops of the benchwork. DIdn’t know if that would affect your answers or not.
Most of my three level layout is 1/4" plywood and 2" foam. With a 2x2 box frame support on the lowest level, it’s plenty strong enough for my 225 lb butt to walk around on!
I use 3/8 with joists on 12" centers with no problem. After you fasten it to the benchwork you can test it for deflection, but I don’t think you’ll have any.
Enjoy
Paul
I use 1/2" plywood (almost standard for house roofs; scrap pieces are easy to get).
Tortoise switch machines say “one inch” for the wire going up through the roadbed to the turnout points. 1/2" ply + 1/2" Homasote + cork leaves maybe 1/16" of wire to trim off. Of course you can always buy and install longer, thicker wire.
I am using 3/4" plywood. I too have read comment after comment , and after having used plywood of every thickness for a variety of projects, and witness the warping and bending of thinner pywood, there was no doubt in my mind that I was going to use 3/4".
For small layouts, and widths of 24" or less, you can get away with thinner plywood, especially if you space supports beneith at sufficient intervals.
But considering the value of what is on top of those tables, doesn’t it make sense to have the strongest surface that you can afford? I know for some of you folks, the cost of 3/4" plywood is too high at $25-$28 a sheet, but what do you pay for ONE engine?
This is sort of like telling someone to use 4x4s for legs. Why bother?
I don’t build layouts out of 1/4" Lauan and 2" foam because I’m a cheapskate or poor. I build that way because it’s fast, an efficient use of my money, and plenty strong for shelf layouts (and my three level is basically nothing but a gigantic shelf). I could have built with 3/4" or even 1/2" ply, but it would have been a waste of my money, considering the added strength of the extra-thickness plywood isn’t important on a non-load bearing shelf layout.
But if it makes you feel more secure, go ahead and use 1/2" or thicker ply. But just think of the extra goodies you could have on TOP of your foam if you didn’t blow that money on wood!
Notice I said…for smaller widths ( ie shelf layouts), thinner plywood is fine. I am taking about layouts on benches, and layouts 30" wide and wider. No one is going to need to climb on a shelf layout.
But is a plywood deck of any thickness really absolutely necessary if you are using 2" of extruded foam? Let’s presume, of course, you have an adequate support frame underneath. Is the foam not rigid and strong enough to support the tracks and scenic elements without resorting to expensive plywood?
By not having a plywood deck …- wiring would be simpler – no holes to drill (in the wrong place), just poke a hole in the foam with a coathanger or awl;
undermounted switchmachines could be mounted closer to the surface by simply cutting a hole for it;
There is no way I could work with a foam only layout. There are places where I need to stand on my layout. Beside, working in O gauge, it is possible to have 10 pound locomotives. For my upper deck I’m thinking about 1/2" OSB with 1/2" foam over that. The lower level is 3/4" plywood with foam or homasote roadbed.
I have used everything from 1/4" up to 1/2 inch plywood on the layout. What I use depends on where and for what purpose I am using it. I would recommend that you use 3/8" plywood and keep the supports no farther than 16" apart. Gluing the plywood is also a good idea. Much of my 3/8 inch base has been down over 20 years and has not warped at all. However! The conditions in my basement stay reasonably the same year around. If your room has wide swings of temperature or (more importantly) humidity, you may want to go 1/2". IMHO 3/4 is major overkill unless you only put supports in every 4’. Consider your total cost for the construction, not just the cost of the plywood.
You are correct Ray, you use what you need depending upon what your layout needs for strength. I have tables that will be 30" wide and wider. I may need to get up on these tables at times, I weigh 185#. I also want the room underneith un cluttered for staging, so my supports are every 4 feet. I also have a well temperature controlled basement location ( as you stated also Ray). This makes a big difference. There is a correct answer for each layout, but that answer depends upon all the factors mentioned by all the guys that answered this thread, bookshelf layouts to not need 3/4", table layouts of 24" or less do not need 3/4"…the layout dictates the construction design required.
Well in my area, 2" foam isn’t readily available, so I’m only going to use two layers of 1/2" foam (which is available) and my layout is around the wall but is 48" wide. The walls/ceiling of the room slope inward (bonus room over the garage) so I will need to climb on top of the layout when laying track along the walls (the hidden main loop). So it will need to support my 250lb fat butt. I think I’ll go with 1/2" ply with 12" joist spacing, glued and screwed.
