Foam vs Plywood - opinions please

Discussion in 'FAQs' started by spitfire, Aug 16, 2006.

  1. spitfire

    spitfire Active Member

    Hi guys!!

    I'm building some new benchwork and I'd like your opinions on the merits of plywood with foam, or just foam by itself. The benchwork is open grid.

    I also have some specific questions for each method.

    For plywood plus a layer of foam
    1. how thick should the foam be?

    If only foam
    1. again how thick?
    2. what about drilling through for turnout control? (I would imagine back and forth movement of metal wire would eventually saw away at the foam. Do you need a liner of some kind?
    3. how far apart to space the benchwork "grid"?

    Thanks in advance!! :D :D

  2. 91rioja

    91rioja Member

    I'm not sure what the rest of the group is going to say, but I am using 3/16" Lauan with 1" blue extruded foam on the top. I have 1"x4" benchwork that is 24" deep and 16" centers and it seems sturdy enough. I am currently in the process of terraforming with the foam, and it seems to be going quite well. I liked the idea of having a base layer, and then building upon it; for my layout, it was the best fit.

    If it were just foam, I would probably suggest going with no more than 16" centers and 2" extruded foam.

    Hope this helps.
  3. 60103

    60103 Pooh Bah

    My personal preference is Homasote for the roadbed, with or without a layer pf plywood under it, and fit the foam scenery on the sides or under the roadbed. (I've never used plywood under the Homasote, but...) I think the Homasote solves most of the track laying problems, especially for switch machines.
    I did the Lionel layout with 2" foam and supports every 16" or so.
    If you go for foam, The thickness depends on how far you plan to go down into the scenery. I'd use 2" for self supporting but 1" or 1/2" if you put plywood under it. You can always glue more foam underneath for a canyon.
  4. Gary Pfeil

    Gary Pfeil Active Member

    I haven't yet laid any track on foam, so can't speak with any firsthand knowledge of it. It sure seems to be popular now, and since it eliminates using a sabre saw to cut plywood, I can see why. It seems gluing a luan plate under the turnouts to mount a machine too works well. I'm not sure how comfotable I'd be with having to glue the track down, but its probably just a matter of getting used to a new technique. I've always been happy with my homasote on plywood. If weight is not a consideration and you don't mind sawing it is a proven method.
  5. Relic

    Relic Member

    Me , I have three inches of foam on an open geid frame with two ft. centres made from 1x3. the foam is covered with cheese cloth painted with Pollyfilla. Since I had no idea what I was doing when I started , some of my layout is four feet wide with the track AT THE BACK in some places (that is going to change) I found (wonder how?) that I could pretty much lay on the thing to reach a wreck and not even crack the plaster
    good luck ....have fun
  6. ezdays

    ezdays Out AZ way

    Going with only 1" of foam, I'd definitely use something under it. On my expansion, 24" wide 'L" section, I used just an open box frame of 6" wide MDF and 1/2" MDF underneath 1" of blue foam. Using the 1/2" MDF, I didn't think I needed to put in any stringers for support. My older section is about 3" of foam on a door, not counting the hills. The difference being that the older section is several different layers of elevation whereas the new section is going to be all flat. But in either case, I have something under the foam for support.

    The foam is probably stong enough to not have any underlayment, 1" is good, 2" is better if they are glued together, but then you would need to add stringers for support. My thought is that even 1/4" plywood would give you additional insurance and I wouldn't risk not having it.

    As far as wire movement wearing away at the foam, I doubt that this would be a problem. Even if the wire moved around a bit, it wouldn't be that significant to warrent putting it in any conduit. If you are still concerned, then you might fill the wire hole up with something like a bit of plaster or drip glue down the hole. I've not done that, but it's a thought.:rolleyes:

    Good luck...:)
  7. spitfire

    spitfire Active Member

    Thanks for all the advice everyone. I must say that spiking into homasote is a very satisfying experience, and I too am a little nervous about simply gluing my track down.
    I'm wondering if perhaps a combination approach is the way to go, with tried and true plywood and homasote for the flat yard section, and foam for the more hilly sections.
    On my last layout, which I'm tearing out before actually finishing it, I found that I could only build up, not down because the stringers got in the way. I want to avoid that problem this time.
    Gary, you answered a question I forgot to ask - how to mount turnout motors when using only foam. I keep hearing about this Luan plywood, but I don't think we have it up here.

  8. 91rioja

    91rioja Member


    I am using the El Cheapo latex caulk to put my track down. I use wite under the WS foam roadbed to the extruded foam, and the clear to put the track down on top of the roadbed. the great thing about the latex caulk, it that it comes up easily (I've had to pull a few sections of track back up so far, and it comes off rather easily). Just my 2 cents worth.
  9. pgandw

    pgandw Active Member


    I haven't tried it yet, but the next time (due to start building after I move) I'm planning to use 1/4" plywood, 1" foam, and Homasote for roadbed on top of the foam (all glued). The plywood and foam will be glued together, and cookie-cuttered and bent over 16" x 24" grid to form various grades and elevations. Cookie-cutter because I want the smooth natural grade transitions from bending the pywood/foam lamination. I'm sure there will be additional risers in some locations to get and hold the exact grade alignment I want. Homasote is essential (to me) for my handlaid track. I figure the foam will help prevent any movement of the Homasote due to moisture absorbtion, and reduce weight and noise from my previous 1/2" plywood subroadbed.

    Had thought about foam for the scenery base between the tracks because I'm modeling a forested region (and I want light weight) but keep coming back to the fact that unless I carve every single square inch, I have basically a flat-top layout with some scenery additions. Not criticizing those who have gone before me (they have done more than I have), but most foam top layouts look like terraced countryside - flat sections with cliffs, rock faces, and retaining walls in between. This doesn't work for modeling Oregon's coastal mountains and forests. Since there will be over 4" difference in track elevations on a 2 ft deep shelf, I need the scenery to be hollow underneath for ease of wiring, installing turnout throw linkages, and possibly uncoupling ramp movers. And if I get ambitious enough, I want to add under the shelf sound and fog generation. To get the slopes, I plan to use cloth window screen with Structolite or similar lightweight plaster substitute as my scenery base. However, I may try experimenting with the folding 1/4" thick foam sheets as a substitute.

    Certainly, there are plety of other good construction methods. But the above seems best for me and my layout.

    my thoughts, your choices
  10. Russ Bellinis

    Russ Bellinis Active Member

    Val, the luan plywood is also sold as door skin material. It is the thin plywood used for facings on hollow core doors.
  11. Doc Holliday

    Doc Holliday Member

    Lots of good suggestions here. I used 1/2" ply with a minimum of 2" foam over all and WS inclines to form grades. I used Liquid Nails for Foam Projects to glue the foam and cork roadbed and lautex caulk for the track. If I built a shelf type layout I'd forgo the plywood, but my entire layout is on rollong casters so I needed the plywood as a horizontal diaphram so when I pulled on one side the rest came with it.
  12. Gary Pfeil

    Gary Pfeil Active Member

    Fred, your post got me thinking. I know from your previous posts you are an experienced and knowledgable modeler. So at first I didn't understand why you would want to use foam if you were still going to use plywood (even tho thinner) and homasote, it seems the weight saving would be negligable, tho perhaps it is important to you? Anyway, my thought is if you go that way, 1/4" ply and foam, will you be using Homa Bed as opposed to Homasote? It's a nice product. I've used it (I handlay too) and it sure beats carting home 4x8's of Homasote and making a mess cutting it, then messing around getting the ballast shoulder to look right.
  13. doctorwayne

    doctorwayne Active Member

    The best arguement for foam that I've seen was a couple of articles in Model Railroader, by Bill Darnaby. The first was in June 1994 and the other in March 1995. He used 2" thick foam, mounted directly to wall-mounted wooden brackets, using Latex Liquid Nails. Then, using a number of purpose-made hot wire cutters, he formed the roadbed. He had different cutters for single or double track, and a different one for sidings, but in each case, he cut the roadbed profile, along with the sub-roadbed profile and the lineside ditches all in one pass. The finished results were very realistic and seemingly very easy to do. However, as for the foam absorbing sound, he found quite the opposite to be the case, and in the second article, he modified the profile of the hot wire cutters and used N scale cork roadbed, unsplit, for the ballast profile, filling in the shoulders with caulking. The idea has appeal for me mainly for the ability to create the realistic roadbed profile, although I'm not sure if scenery would be very durable. I seriously considered it for my second level, but I'm probably going to go with 3/8" sheathing plywood over 1"x2" pine open grid framework, 16" o.c. I'll be mounting a bunch of four foot double tube fluorescent fixtures to the underside of this, so strength is a consideration. Around here, I've only seen the foam available in 2'x8' sheets, with shiplap edges. The layout will be about 30" deep, and, by the square foot, plywood is cheaper.

  14. Clerk

    Clerk Active Member

    Val. I agree with Chris. I have 1 x 4 and 1 x 3 bracing on 16" centers, One layer of 1/4" plywood and 1" foam on top of it all . Works very good and the foam allows me to dig out small lakes and other things. Some modelers use 2" foam but I think that is to hard to handle.
  15. spitfire

    spitfire Active Member

    Gentlemen, thank you all for your advice and opinions. :thumb: I think the combination sounds best - thinner plywood with 1" foam.

  16. pgandw

    pgandw Active Member


    I've used 1/2" plywood and Homasote before, and nothing wrong with that combination. However, in lurking on the forums I've seen a lot of folks complain about dimensional stability of both plywood (and it's supporting wood frame) and Homasote under changing moisture and humidity conditions. I never had a problem myself, even though the layout moved from Coos Bay, Oregon to Pensacola, Florida to Ft Lauderdale, Florida. Only the Pensacola house had air conditioning. But I'm beginning to worry that I just got lucky. I figure the foam glued to the plywood and Homasote will add some more stability.

    2nd reason for foam is the front right corner is a harbor with a dock. I want the dock to be about 1.5" above the water (10 scale feet). If I extend the plywood for the water base, the foam and Homasote will give me about the right height for the tracks on the shore leading to the dock.

  17. Milepost131

    Milepost131 New Member

    Plywood,homosote,foam etc. been there, done that

    I've used just about every form of benchwork there is in the last 40+ years.

    Right now my "current" layout is 2" foam with 1/2" plywood under it. I'm N scale. Code 55 and all scratchbuilt turnouts. In a basement environment. (So why all the detail?)

    Basements have a tendency to "change" benchwork. Temperature and humidity fluctate. My experience with homosote in a basement in the humid south was that my poor dehumidifier cranked and cranked and there WERE changed in height (thickness) and some minor alignment.

    When I started planning this layout I wanted to eliminate potential problems.

    The 2" foam could PROBABLY be sufficient by itself BUT I knew that at some point I might LEAN on it too much and cause a major "sink hole" so I support it with the plywood. I sealed the plywood.

    Some thought the foam would act too much like a sounding board. I use Woodland Scenic foam for roadbed which helps some and the plywood dampens the sound too. I've found that scenery (hardshell) dampens the sound a bit too.

    THe ONE issue I've had with the 2" foam is how to build turnout controllers for my Code 55 turnouts! The "rod" that penentrates the layout is longer than I'd like. Yes I could burry it IN the foam but reasoned that UNDER the layout was better for maintenance.

    I HIGHLY RECOMMEND my method of open bench work framework but with solid sheet 2" foam. BTW, that 2" foam allows some "sculpting" of scenery below grade. I've (seemingly) eliminated "alignment" issues in a basement caused by temperature and humidity. My track "adjustments" are at a minimum.

  18. sumpter250

    sumpter250 multiscale modelbuilder

    For whatever it's worth, my opinion of foam is, foam is used to fill space, it is never used as a structural component, and never, never used to lay track on. Even my poratble modules have plywood subroadbed, and either homasote, or cork roadbed. Yes, every year the modules seem to be heavier than the year before, but after twenty years, they are still solid, and have never needed track repairs. I honestly can't say that about track laid on foam.
  19. Gary Pfeil

    Gary Pfeil Active Member

    Fred, regarding the humidity problems with Homasote, my basement has radical swings in humidity, extremely dry during the heating season, and humid as could be in the summer. I've had problems with my staging tracks which are flex track on plywood, no Homasote. The problem is caused by the track nails which get closer together when the wood dries. However, even here once I cut the rails the width of a cutoff disc, the problem went away.

    Where I have Homasote on plywood I haven't experienced any problems. I do paint the Homasote and plywood with latex paint, leaving no bare areas at all. Then when I glue down ties and ballast, using a fair amount of alcohol and water, I've had no problems. Throughout 8 years now I've had no evidence of any kinking, etc in my handlaid track.

    Regarding the kerfs in the Homa Bed, I filled them with spackle. So far, no problems with spikes working loose. If I were concerned I'd consider a small dab of super glue on each spike head and let the tie hold it.

    I saw an internet article on using grape vines for logging railroad ties too. And the pics were awesome! As I recall, they were sanded top and bottom to provide flat surfaces, that was about it.

    Are you going to be living in Fort Lauderdale w/o air conditioning? I can't imagine!
  20. pgandw

    pgandw Active Member

    Ft Lauderdale (actually Hollywood) was in my younger past. I was there from '78 to '82 in my very first house that I bought (for $44,000!). There was usually just enough ocean breeze that when combined with ceiling fans it was reasonably comfortable. However, there were usually 2-3 weeks a year in August when the ocean breeze died and it was miserable. We had 2 window air conditioners to help us survive those days. Installing central air would have meant major rebuild of the house, which was beyond my means.

    In 1993, I got lucky and was transferred to Alaska - spent 6 years there - and then moved to San Francisco Bay area, where I am now. I have completed my Coast Guard service and am looking forward to relocating, but no futher east than the Rockies, unless it's north of Massachusetts in New England. I've been spoiled by the mountains and reasonable summer humidity and temps. As soon as I find a reasonable job in a suitable place, we're out of here!

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