Plywood subroadbed warping?

Discussion in 'N / Z Scale Model Trains' started by SD90, Oct 14, 2003.

  1. SD90

    SD90 Active Member

    Has anyone had the plywood subroadbed warp after using plaster soaked cloth on it? Someone told me this might happen to my layout when I start doing scenery and ballasting. I used 1/2" plywood with risers mounted about every 16-22". Any info on this would be greatly appreciated!

  2. Matthyro

    Matthyro Will always be re-membered

    Mike 1/2 inch plywood is very sturdy and you won't be soaking it so it should handle cloth with plaster OK. I have 3/8 plywood screwed down at every 12 inch . and it handles paper towel soaked in plaster fine.
  3. Vic

    Vic Active Member

    You shouldn't have any problem with 1/2" plywood warping. The small amount of moisture that gets on it ballasting or building scenery is not enough to do any damage.

    What does cause trackage to have a "roller coaster" look is not from warpage but improperly spaced and constructed risers. Risers and joists should be no more than 16" on center and risers should be constructed as shown in the following pic using a cleat. By placing the cleat approx. 1/8" above the riser the load (plywood subroadbed) is more evenly distributed and "humps and sags" don't occur.

    Hope this helped.

    Attached Files:

  4. Bikerdad

    Bikerdad Member

    Warping plywood

    If you want to minimize plywood warping, then you need to seal the wood. Paint, varnish, shellac, or lacquer will all do the trick. Warping of plywood is caused by moisture, which can be absorbed directly OR through the air. Sealing vastly slows the moisture transference, which can occur regardless of your scenery materials.

    Paint and/or varnish are my suggestions, because both are fairly tough and inexpensive, although varnish is preferred because it is virtually impenetrable to liquids. Shellac is easy to use, inexpensive, non-toxic, and easy to repair. Unfortunately, alcohol is a solvent, which can be problematic if you're using alcohol in your scenery work. Lacquer is not as easy to apply (not that it matters, since you're going for a protective coat, not a finish coat), dries very quickly, and is easy to fix. The downside to lacquer is the fumes, nasty, nasty stuff. It'll give you bad flashbacks to sitting at the beauty parlor waiting while your mom gets her nails done! Finish BOTH sides of the plywood, as well as all exposed edges. The edge finishing isn't nearly as important as doing both sides, but it does help cut down on the collection of splinters. Just because YOU can't see the underside doesn't mean that the moisture can't get to it, and finishing only one side will, depending on your climate, almost guarantee warping.

    If you don't want to use varnish, then use some leftover paint. Don't have any? Go to the Borg and pick up a quart of "oops" paint for a buck and have at it. If you have young kids available, this is a part of the train stuff that they can participate in.

    In accordance with the Addy Protocol (developed by Forrest Addy to give readers a sense of a poster's expertise regarding the subject) : I'm an utter newbie to model trains, BUT, I've been woodworking for 5+ years, and have used all of the above finishes in that time.

    Grace and Peace, BD
  5. txcavgr

    txcavgr Member

    Timely topic for me, about to start working on module number one for the new layout. Decided on a 1 x 3 grid with 12" spacing. I was thinking about 3/8" plywood for my subroadbed. My last couple layouts were on foam or on a stress-skin panel.

    Opinions on 3/8 vs. 1/2" plywood?
  6. DanRaitz

    DanRaitz Member

    Mike and gang,

    It's not the thickness of plywood that can be a factor in warping. It is the number of ply's, or layers in the sheet of plywood. I made the mistake of building one layout using 1/2" plywood that was only 3 ply (it was cheap). Needless to say there was no strength to the subroadbed, it kept sagging all over the place. In the end it was tore down and every layout since then has been built with plywood of at least 5 ply.
    Just for you information.:D
  7. SD90

    SD90 Active Member

    Thanks for the info guys!


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