Plywood + Foam, just plywood, or just foam?

[montanan]

I am old school. Most everything was done many years ago and I was using Floquil paint which is no longer made. Scalecoat would be my next choice. That's what I have used since Floquil went off the market. They have a very good selection of railroad colors. I have used some acrylics for painting smaller details such as windows and doors.

 

[Raincoat2]

Again, thanks, Chet. this is good information for a newby to have.

 

[beiland]

Foam Only?

Hi, everyone. I'm building my first "real" layout, an HO scale "around the walls" in an 18' x 12' basement room. I've built the support infrastructure and now ready to put on the top. I've watched youtube videos and read articles in mags and online until I'm blue in the face, and totally confused. My question is what to use: plywood only, plywood + foam layer, or just foam layer?? Everyone's got rationales for their approach - all seem to have advantages and disadvantages. I'm stalled in construction right now because of this question, and need to move forward, but I want to get this right from the start. I'm still listening. Any suggestions? Past experiences good and bad?

I was interested to see where this subject thread might wander to as I am also contemplating an around the wall 12x16 layout, double decked. With potential supports every 22-24 inches (stud spacing of shed) I had thought the use of 2' foam as a roadbed was a viable option,...foam only ??

But I have not seen many (any) folks in the subject thread taking up that cause? In all of your research Raincoat did you find some good reasoning to consider such a construction?? It would seem that applying lots of 'stick-up' features to such a sub-roadbed would be easier, and making lots of terrain variations (hills and mountains) out of glued together foam blocks would be much easier.?

Granted the track laying problems would have to be considered more deeply, as I can remember my going back and tweaking things was done quite often before the final 'contour' was arrived at (so any permanent bonding would have to wait for a final curtain call).

I think the 'every 24 inch support' under the 2' foam (blue foam) is enough??

I think there is a big club layout on this forum that documents a mostly foam roadbed approach (can't remember where to find it at the moment) ??

 

[beiland]

....
I think there is a big club layout on this forum that documents a mostly foam roadbed approach (can't remember where to find it at the moment) ??

Found it...

Just happened across this video presentation,...a big club layout with lots of foam board utilization. Wait for the ride around the layout and you will see lots of it.

[url]https://www.youtube.com/watch?v=J1_skG7LRKE[/URL]

Recently I came across a reference (subroadbed discussions) that recommended gluing the track down with a rubber based adhesive, ....Pliobond I think it was.
I like the idea as this would be 'elastic' enough to allow a bit of track movement under extremes of temperature and humidity?

Brian

 

[Red Oak & Western]

Joe Fugate (Siskiyou Line, editor MRH) wrote an article on the problems of using foamboard as a base: http://mrhpub.com/2016-09-sep/online/html5/index.html?page=284&noflash

I've been using Homasote forever, it's available at the local lumberyard and Home Depot and Menards (but not Lowes), and is easy to work with. They (Homesote) now call it "440 SoundBarrier", but I can't tell the difference between what I bought last month and what I used 30 years ago.

 

[beiland]

I don't think they have Homasote in Florida

 

[Chevron_GATX]

N-scale layout sub-roadbed: OSB + 2" polyiso foam.

I don't think foam-only sub-roadbed is a good idea since foam isn't really strong enough. Half-inch plywood with two-inch foam is the most popular method, and I think most practical for most layouts. At first I used 1/2" melamine (now I'm using 1/2" OSB), and a two-inch layer of polyisocyanurate foam, which is sold under the trade-name, R-Max Thermasheath 3 at Home Depot, also known as polyiso foam for short.

Polyiso foam is easier to cut and shape than extruded polystyrene (the pink or blue stuff), doesn't make a mess, and readily accepts solvent-based spray-paints and glues without melting. It's also extremely dimensionally stable according to a recent six-year industry study of roofing insulation materials. The only downside to polyiso is that it's covered on both sides with a thin sheet of paper-backed foil (I just paint over it). The foam cuts easily with a box-cutter type knife, and shapes with just a 3M sanding sponge. Here's a piece of polyiso I painted primer-gray:

For my trackbed, I'm using 3/4" Woodland Scenics risers to elevate my trackwork slightly above-grade. I think this will make various grades surrounding the track easier to do. I've also built a number of Structo-Lite and Celluclay landforms on 1/4" Foamcore bases, so this slight elevation will allow me to set these at-grade more easily as well. I'll build up other above- and below-grade landforms to meet up with the Woodland Scenics' risers using one or more of my three basic bulk-scenic materials:

• USG Structo-Lite (gypsum plaster with granules of Perlite mixed-in; only $11.30 for a 50-lb. bag at certain Home Depots).
• Activa Celluclay paper-mache (only $12.49 for a five-pound bag using a Michael's 50%-off coupon).
• DAP Plastic Wood (used to fill-in small gaps; $8.98 for a 32 oz. tub at Home Depot).

I also color all of my materials with Quikrete liquid concrete colorants while mixing for color all-the-way-through. These colorants are really concentrated and a little goes a long way. Using concentrated colorants, I won't weaken or compromise my materials' strength by using latex, acrylic or tempera paints (which require much more product to color).

I still have to cover the risers and build a grade, most likely using Activa Rigid-Wrap plaster cloth which seems like the best deal at about $16 for five-pound box on Amazon. Below is the polyiso sheet sprayed with a textured spray-paint. Once dry, I sprayed the foam with 3M Super77, then I sifted a layer of Polyblend non-sanded grout all over the surface (I later discovered that sprinkling the grout then spraying liberally with scenic cement yields better much better adhesion):

 

[Red Oak & Western]

I don't think they have Homasote in Florida

They do in some areas. Being unfamiliar with Florida, I checked Miami. It has 2 stocking dealers. Go to http://www.homasote.com/wheretobuy? and enter your info.

 

[logandsawman]

Hi,

I know this is an age old discussion that surfaces frequently. I used plywood for everything as the base and was very happy with it. For inclines, I used thinner plywood and let it make the slope. I always felt confident that I could get a really tight bond of track to the plywood. Also, I liked drilling my holes in the plywood.

[video=youtube;JCTcpJ2Ffe8]https://www.youtube.com/watch?v=JCTcpJ2Ffe8[/video]

This is the beginning of my layout. I finished it in about a year. I used different thicknesses of plywood in different places.

hope this helps someone. LASM

 

[beiland]

OSB + 2" polyiso foam:

I don't think foam-only sub-roadbed is a good idea since foam isn't really strong enough. Half-inch plywood with two-inch foam is the most popular method, and I think most practical for most layouts. At first I used 1/2" melamine (now I'm using 1/2" OSB), and a two-inch layer of polyisocyanurate foam, which is sold under the trade-name, R-Max Thermasheath 3 at Home Depot, also known as polyiso foam for short.

Isn't the OSB quite a bit heavier than plywood?

I can't help thinking that the combo of 1/2 plywood and then 2' foam is overkill for HO trains?

Polyiso foam is easier to cut and shape than extruded polystyrene (the pink or blue stuff), doesn't make a mess, and readily accepts solvent-based spray-paints and glues without melting. It's also extremely dimensionally stable according to a recent six-year industry study of roofing insulation materials. The only downside to polyiso is that it's covered on both sides with a thin sheet of paper-backed foil (I just paint over it). The foam cuts easily with a box-cutter type knife, and shapes with just a 3M sanding sponge. Here's a piece of polyiso I painted primer-gray:

Is the pink foam polystyrene foam?

For my trackbed, I'm using 3/4" Woodland Scenics risers to elevate my trackwork slightly above-grade. I think this will make various grades surrounding the track easier to do. I've also built a number of Structo-Lite and Celluclay landforms on 1/4" Foamcore bases, so this slight elevation will allow me to set these at-grade more easily as well. I'll build up other above- and below-grade landforms to meet up with the Woodland Scenics' risers using one or more of my three basic bulk-scenic materials:

Again to me it appears that your sub roadbed plus roadbed combo is a bit of overkill.? I mean while it is great, I just don't see that much material is needed??

 

[Red Oak & Western]

The pink (Owens) and blue (Dow) foam insulation is Expanded Polystyrene. The white stuff, that you don't normally want to use, is Extruded Polystyrene. Many use 2" foam not for its strength (which is limited), but for the ability to shape the landscape around the railroad features.

 

[Chevron_GATX]

Isn't the OSB quite a bit heavier than plywood? I can't help thinking that the combo of 1/2 plywood and then 2' foam is overkill for HO trains? Is the pink foam polystyrene foam? Again to me it appears that your sub roadbed plus roadbed combo is a bit of overkill.? I mean while it is great, I just don't see that much material is needed??

Hey, there, beiland! I'll answer your questions one at a time:

• Not sure about the weight, but I bought a piece of OSB because I had to extend the center Unitram section by a few inches. I chose OSB only because it was cheap. A sheet of half-inch, 4' x 8' plywood here costs about $50.
• If it's overkill for H0, then it's even more so for my N-scale layout! This layout was built sort of catch-as-catch can with no real plan. I chose the melamine simply because I didn't want to look at bare plywood until everything was completely scenicked.
• Pink (Owens-Corning), blue (Dow), or green stuff (Lowe's house-brand) is extruded polystyrene (XPS) where the color is simply a matter of the manufacturers' branding choice. I built my layout on polyisocyanurate foam which has certain advantages over XPS (e.g., accepts spray-paint).
• Again, my sub-roadbed was built without any planning or much knowledge about conventional benchwork.

Another reason I chose polyisocyanurate over XPS, is that XPS isn't regularly stocked at Southern California Home Depots. But, now, I'm glad they aren't, since as a result, I have a foam sub-roadbed that's much easier to shape and paint. Polyiso is also a recommended material used in Bragdon's Geodesic foam scenery method.

 

[Chevron_GATX]

The pink (Owens) and blue (Dow) foam insulation is Expanded Polystyrene. The white stuff, that you don't normally want to use, is Extruded Polystyrene. Many use 2" foam not for its strength (which is limited), but for the ability to shape the landscape around the railroad features.

I'm sure it's just a simple mistake, but that's actually backwards: Extruded polystyrene (XPS) is the pink or blue stuff (this is what you want). Expanded polystyrene (EPS) is the white beaded-foam they make coolers and disposable coffee cups out of (the stuff you don't want). This material is commonly (and, erroneously) referred to as "Styrofoam" (oddly enough, Styrofoam, a trademark of Dow Chemical Co., is actually XPS, and not the EPS it's commonly referred to as). EPS is still useful for making bulk forms on top of which you plan to use other materials.

I try to save large pieces of EPS and cardboard packing forms to use as a bulk, base-forms onto which I can construct a Structo-Lite, Celluclay, or plaster-cloth top-layer. For example, I built this Structo-Lite mountain on top of a large cardboard packing form that came in the box my HP laserprinter was packed in:

USG Structo-Lite + Quikrete colorants + cardboard packing form on top of a sheet of 1/4" Hardiebacker tile underlayment.

 

[beiland]

Just found this on another mailing list..

I use the very cheap and unstable 5/8" stranded plywood with the best 1x4s glued and screwed on edge on16" centers. Let the wood just set in your Train Room for a few days so it stabilizes to your Train Room's relative humidity. Legs are cheap 2x2 furring strips bolted to the vertical 1x4s with appliance leveling feet. I then place at least two layers of very, very stable insulating foam boards on top, staggering joints only pinned with hardened finishing nails and wood skewers enough so the foam doesn't slide off. Only glue the foam together, do not glue the foam to the plywood. I glue roadbed and track to the foam after carving contours into the foam.

....basically pretty strong and relatively inexpensive with the foam "floating" on top.

 

[beiland]

...and this from that same subject thread

Many years ago Kalmback published a benchwork softback book by Linn Westcott, one of the grand daddies of model railroading. There's more than one way to go about framing a layout. Linn made me a believer in wall brackets secured to the wall with 2x2 vertical pilasters. He also pointed out that the ideal support locations for supports are not 16 inches or 34 inches at one fifth and at 4/5 along your L-girder.

Example: using a 1x3 L-girder with 1x2 flange, the distance between your two support brackets can be 9'6". That, sir, saves you a lot of time and material. Using a 1x4 L-girder increases the spread distance to 13' It's all the strength offered by the flange.

If you want to see some of these and other methods seldom used, go to the files section and look for New York Kittatinny and Western.
Bernie Halloran

 

[beiland]

another...

I have used Home Depot's Sandiply extensively! I use it for my railroad and also for cabinet work I do as a hobby!
I can tell you from experience that if you take it out of the store and do not let it acclimate to the environment you are going to use it in for at least 2 weeks you are in for a lot of trouble! This plywood will suck up water like no ones business!
I used it to build the deck for my Williamson freight yard. the yard is 40 feet long and 4 to 6 feet wide. I picked up 10 sheets and brought them down the basement. I stacked them onto the top of the bench work and heavily clamped them in place for 3 weeks. I then cut and installed them making sure to make good seems with a lot of biscuits and a wide plate screwed and glued at each seem! I now have a very flat surface to work with! One sheet which was left over was left standing on it's edge and it curled badly even after being down there for a month! SO the key to using this stuff is in keeping it straight and then properly anchoring it with good seems.

Would I do it again? For this large of a flat surface the cost was a small issue about $26 bucks a sheet vs $50 for cabinet grade cabinet plywood! The latter cannot be purchased at either Lowes or HD. It has served it's purpose! Would I use it in a HIGH END piece of furniture NO! Would I use it in shop cabinets and such sure!
When building a smaller layout that you know is going to be there for a long time Buy the best plywood you can afford! After that choose the best to suit your needs!
Ray Russell Sr.

 

[beiland]

...a series of replies just posted on that subject thread...

Last summer/fall I built the basic framework for my layout in my basement. The frame is 2X4's and the road bed is a sandwich made of 5/8" strandboard and 1/2" homosote. The entire structure is a 32' long dogbone with the ends about 7' wide and the center about 4 1/2' wide. I glued 1/4" cork road bed on top of the homosote and nailed the flextrack in place using #19 X 7/8" brads. I've installed numerous turnouts in the mainline and ran trains in both directions at various speeds without any derailments

However, now, December 24, I have numerous kinks developing in both the straight and curved tracks. Also, the track is out of level at many places around the layout. Needless to say, it's almost impossible to run trains at all.

Have any of the forum members had this type of problem? I can't decide if the track expanded, or did the road bed shrink? Whichever it is, what can be done to fix it and what can be done to eliminate the problem?
Thanks,
Walt

Walt, I cannot help.

I have switched to using blue foamboard exclusively on all my layouts. I first did this around 1990 and have not looked back.

Basements are notorious for moisture problems. Even when you can't see the moisture.
A dehumidifier will help with the airborne moisture---next time.

I had real problems with a layout in a heated garage in Alaska.

I learned to lay my straights in a S curve with the track tacked only on the ends and one tack in the middle. This way the track could expand and shrink with the weather changes.

I now build only in a bedroom on the main level.

Lance Mindhelm recommends not soldering track but putting a rail joiner on each joint.
I also find cutting gaps into the rail using a Dremel tool and a cut-off disk to be helpful.

Back in my early days in the hobby I would buy my lumber and put it into the layout room for a month to let it "climatize". I don't know if that helped or not.

Sorry for your problems.
Most of us have been there at one point or another.
Darryl Huffman

I think you could have two issues. My guess is the problem with sagging is the strand board (OSB). In my opinion OSB is simply not a good structural material and Homasote was never designed to be structural. You don’t describe what sort of intermediate cross supports you built, but if it is unsupported across its width, I will guarantee OSB and Homasote will sag. Even quality plywood will sag if not well supported. The other issue is whether or not expansion space was left between sections of rail. It doesn’t have to be much, the thickness of a credit card should do, but over a 32’ length, the rail will expand and contract and it will kink if there is no room for expansion.
Jim Marlett

 

[beiland]

Hey, there, beiland! I'll answer your questions one at a time:

• Not sure about the weight, but I bought a piece of OSB because I had to extend the center Unitram section by a few inches. I chose OSB only because it was cheap. A sheet of half-inch, 4' x 8' plywood here costs about $50.
• If it's overkill for H0, then it's even more so for my N-scale layout! This layout was built sort of catch-as-catch can with no real plan. I chose the melamine simply because I didn't want to look at bare plywood until everything was completely scenicked.
• Pink (Owens-Corning), blue (Dow), or green stuff (Lowe's house-brand) is extruded polystyrene (XPS) where the color is simply a matter of the manufacturers' branding choice. I built my layout on polyisocyanurate foam which has certain advantages over XPS (e.g., accepts spray-paint).
• Again, my sub-roadbed was built without any planning or much knowledge about conventional benchwork.

Another reason I chose polyisocyanurate over XPS, is that XPS isn't regularly stocked at Southern California Home Depots. But, now, I'm glad they aren't, since as a result, I have a foam sub-roadbed that's much easier to shape and paint. Polyiso is also a recommended material used in Bragdon's Geodesic foam scenery method.

BTW, I wasn't trying to be disrespectful with my comments, its just that I have seen a good number of layouts over the years that appear to be structurally overbuilt for the weight they are to contend with. I'm now coming to realize that a lot of that 'heavy weight construction' appears to be an effort to off-set the thermal & moisture expansions of our selected roadbed and sub-roadbed materials,...ultimately resulting in track distortions.

It almost makes me want to go back and give more serious considerations to spline roadbed construction technics.

PS: I took a look thru some of my old VHS tapes and found that one by Bragdon's Geodesic foam construction,...still in its original packing,...never viewed by me....ha...ha

 

[Red Oak & Western]

I'm sure it's just a simple mistake, but that's actually backwards: Extruded polystyrene (XPS) is the pink or blue stuff (this is what you want). Expanded polystyrene (EPS) is the white beaded-foam

Yup. That's what I get for trying to play on the forum while eating lunch. The only place I've used the "white stuff" is as an unsculpted filler between layers of the pink/blue.

its just that I have seen a good number of layouts over the years that appear to be structurally overbuilt

I've never worried about the structural strength of the materials I've used over the years. I started with L-girder topped with a 1/2" plywood + 1/2" homasote sandwich. It worked and I've never bothered to change. I pay about half of what Chevron does for a sheet of 1/2 ply ($26 about 3 months ago) and $22 for homasote. With 2" XPS running $35 per sheet, I use hard shell for hills (since my road is set in the {true} midwest, we don't have mountains).

 

[Chevron_GATX]

BTW, I wasn't trying to be disrespectful with my comments . . .

It's all good, man! Interesting series of post-quotes, beiland!