1" Polystyrene on 5/8 plywood...good enough?

[Anonymous]

Still mulling this over.  I have the option of using some very dense 2 1/2" polystyrene pink board which would not even need a wood backing if used in 24" widths on shelf brackets off studs (for some section of the layout)

or

5/8" plywood (or 3/4" if necessary) with 1" slightly less dense polystyrene pink caulked down on top.

or  a combination of both...just setting the benchwork heights different between the modules.

Appreciate thoughts on this.

[SpaceMouse]

 Either would be okay probably. The determining factor is really the distance between the (joists) supports. 

[Hamltnblue]

I would go with the thicker foam and between 1/4 adn 1/2 inch plywood as a base.  The plywood comes in handy if you want to mount switch machines and does add stability to the frame work.

[nucat78]

Unless you plan on putting a lot of weight on it, I think 5/8-in plywood is overkill.  If you want to keep the weight down, laminate foam or use thicker foam and thinner plywood.  I've had no sagging of 2-inch foam on 16-in centers with nothing under it aside from an occasional Masonite splice plate.  Mind you, I did not have huge amounts of plaster scenery on it nor did I climb on it (it was a shelf layout).

 

 

 

[Anonymous]

nucat78

Unless you plan on putting a lot of weight on it, I think 5/8-in plywood is overkill.  If you want to keep the weight down, laminate foam or use thicker foam and thinner plywood.  I've had no sagging of 2-inch foam on 16-in centers with nothing under it aside from an occasional Masonite splice plate.  Mind you, I did not have huge amounts of plaster scenery on it nor did I climb on it (it was a shelf layout).

Thanks for the input fellows.  I really appreciate bouncing these ideas off those of you with experience before I go down and commit some $ to the plan. 

I agree that the plywood under the 2" or 2 1/2" foam board that I want for the "shelf" section of the layout would be overkill.  I am sure I will just place it on large shelf brackets which come out on 16" centers from the wall framing.  Or I will caulk it to some mahogany veneer I have sitting around that looks about 3/16 or so.

I say 5/8" under the 1" because this section will be large parts of the "dogbone" part of the layout and on the "table-top"of the benchwork frame. I have three of these areas will be about 6' X 8' in span.  I will have center "joists" within that.......but mainly, after looking at the sheets down at the local store, the stack of 5/8' look a whole lot flatter than the 1/2" at the moment.

[modelmaker51]

I built all my benchwork with 2x4 framing (16" on center) with 1/2" plywood and glued and screwed 2" foam on top of that as a base.

This gives superior structual integrity over the long run and cuts way down on the noise.

[dehusman]

I would go with 1/2 or 5/8 in plywood and skip the foam altogether.

[HHPATH56]

Maybe it's because I got into model railroading many many years ago, I don't see the purpose of the polystyrene at all. I use cork below the ties, and use 5/8" plywood for my base. I cut and reinforce harbors, and ravines, and build overpasses and mountains from the plywood. Placing switch motors under the plywood requires only the usual control wire to the turnout. I have 260 yds. of track and 110turnouts (of which 96 are electrically controlled) What is the purpose of using 2-3 inches of polystyrene ??? Bob Hahn PS Just got back from the NMRA75 Convention. It was great, as was my 65th High School graduation reunion, July 18, in Milwaukee !