Foam

Note: missed the comment about having to order foam by the truckload... if you can find it though....

I use Pink (it also comes in blue) Styrofoam insulation board - not the beadboard stuff.  As the link indicates, it can be found at Home Depot and similar stores. 2" is plenty thick for stability, especially since you are going lightweight, and it can also be stacked and carved for terrain features both above and below the track level. 

I wouldn't have it totally unsupported though - you should have some sort of joist/stud every 16" or so underneath it to support it. Build a box frame out of 1x4's and put the foam on top. Front with 6" wide Masonite^tm fascia to hide the benchwork and the foam. 

When it comes to mounting switch machines,  use appropriately sized squares of 1/4" Lauan plywood glued to the foam to mount them on. Watch out that you don't put a switch directly above one of your joists. 

Lightweight + Homasote?

Homasote isn't particularly light in weight, and doesn't have the rigidity to be used as a SUBroadbed without additional support, assuming you were planning to use it flat.  Some guys have good luck using homasote spline, with the material placed on edge to provide more strength.  The fact you couldn't find it might be a good thing, since you could have been setting yourself up for trouble.  I have heard of some people having success using Homasote subroadbed, but there are many other accounts of problems with Homasote sagging between supports.  It's much better suited as a roadbed material used atop a rigid subroadbed base.

Is the weight concern out of a need to make your layout portable?  Plywood is hard to beat for strength and stability, especially if the only time you'll be hauling it around is during initial construction.

Pink Foam

Did not see any at my local Home Depot, but there is another within decent driving distance. Does it come in varying thicknesses? My benchwork has supports every 12 inches, so the warnings about placing switches is well taken as is the luan support for machines underneath. This might be an answer since I'm using luan for a backdrop surface. Most of my swithches are ground mount hand throws within easy reach; the ones with machines will require careful placement. I'm assuming that the material can be drilled through for throw rods.

Most of the "people" at these type of stores haven't a clue about insulation and carving etc. as they usually tend to show you the stuff that shreds or is unsuitable in some fashion. It's great to have friends here to help guide you.

Sheet Foam at HD

http://www.homedepot.com/Building-Materials-Insulation-Sheathings/h_d1/N-5yc1vZbaxx/h_d2/Navigation

Varied thicknesses

The link from LK&O above indicates that it comes in 4 thicknesses - 1/2", 3/4", 1", and 2"

Drilling is easy, if a bit messy. Take a look at the throw of your switches before drilling to avoid drilling too big a hole.

Hand Throws

"Most of my swithches are ground mount hand throws..."

If you plan to use foam, make sure you provide adequate mounts for the hand throws as well as the under-roadbed machines.  They're easily thrown out of adjustment through nornal use if not installed securely.

Hand throws

Personally I use a bit of cork roadbed flipped upside down to mount my Caboose Hobby thows.

Not at all stores...

You may have to search around for the Owens Corning pink foam. Home Depot does carry it, but it tends to be regional, and some stores might not even have in their computer database. Prices for 2"  should be around $25 per 4 x 8. That's about half of what other outlets charge for the same item.

Best thing to do is to go to homedepot.com or call and ask whether their store carries it, and if not, then ask if they can check some of their nearby outlets. Although I have a dozen or so HDs within easy driving distance, I found that only two of these stores carries the stuff. The other stores don't even know what I'm talking about when asked. Good luck.

Cheers!
Marc

homasote

there is a company in california called california roadbed that you can purchase your road bed precut and ready too use. this might be a good option for you.   raildad

Roof insulation foam.

There was an article in MRC in the March 2011 issue about making benchwork with poly iso foam.  It is a sandwich product some what like the foam core found in art and craft stores, but it is thicker and uses fiberglass felt on the sides instead of paper.  It is found either in the roofing supply section or at a roofing supply company.  I think the main purpose of the product is to insulate open bean ceilings and other types of roofing where there is not an open space available for batt type insulation or blown in types.  In th earticle in MRC th author has been using the poly iso foam instead of plywood to construct his benchwork.  The homosote that I have is also heavier than a similar thickness of plywood.  

Poly Iso can be a hazard

Iso is from Isocyanate-  gasses out when burned.         I know... you don't intend to burn it... but why invite it in?

Most Depot stores can custom-order materials, but I have no idea about minimums. 

As mentioned... Extruded Polystyrene is the dense-foam insulation.  Expanded PS foam is the 'beady' stuff... made with PS + steam inside a mold in  a popcorn fashion.   The Homosote material is basically felt made of coarse wood fibers. pressed into a thick board... in the '50s (maybe '60s, too),  you could get construction Sheathing with a vapor barrier included. 

But note, also, that homosote can easily absorb moisture and, thus,  is subject to Lots of warping!  I used Interior grade 1/2" ply for good reason... 6 years out with NO problems.

Peter is right - do not use

Peter is right - do not use Poly-Iso.  I worked for a roofing contractor for 25 years (in the office)  and have been around this as well as other rigid foam insulation boards.

What is the difference.  Poly-Isocyanurate usually comes faced with an asphalt saturated fiberglass mat that the roofing adheres to.  If you pinch a little of the foam off, it will tend to disintergrate when pressed between your fingers.  It will have a very gritty sand-like feel.  Any time you brush against it (or tried to "carve" it), you will rub some of the "foam" off and it will fall to the floor or go into the air - which mean into your lungs.  It is abrasive, irritating to the eyes, skin and lungs.  And you all know about what fiberglass does to you.  The only way I would consider using this indoors is if I had a way to completely seal the edges and then place it in some kind of frame (while outside) so that the edges could not be touched.

The pink and blue foam boards are Extruded Polystyrene.  They usually do not have any kind of facing.  These are ok to use.  If you pinch a little off, it will break off in a small chunck and you can compress it between your fingers and it will just flatten out.  It will not disintergrate.   It is like the stuff foam egg cartons are made of.  It is easy to carve (See Scarpia's "22 Stories up - Module 1),  and since it stays in chuncks it is a lot easier to clean up - it will not turn into sand.  It is also not irritating.

I hope this helps.

Thanks, guys!

I read the article in RMC and thought that the stuff sounded great.  Don't the "dead tree mags" ever check for safety issues before they print an article inviting every body in the country to use the "latest & greatest" new material?

The error is ours...

because WE are hobbyists, and eager to contribute from what we know... and make honest omissions, or outright mistakes!  

I didn't see the RMC issue this was in (as you say) but have often considered their ideas when 'inventing' my own solutions.   So, they did the same with the author's input, and had no feedback prior to printing...

Wow! I see Joe's admonition come into focus... Provide Feedback!   This is like contributing to a hobbyist's building code... it reduces the potential of disabling diseases and outright safety hazards!  

The 'safe' art materials program got started by some sudden awareness of the  chemicals used in pigments.  There are many "wonder products" with huge pitfalls in them when used in a way that does Not conform to manufacturer's specs.....  can you believe Teflon is one?

Let's be Careful out there!

1/2 inch A/B exterior plywood and Homosote

For 40 years I have used both 1/2 inch and 5/8 inch thick plywood and tend to use the 5/8 thick more often with a layer of 1/2 inch thick Homosote which is a compressed paper product and needs to be sealed with laytex or acrylic paint before any track or scenery to keep the homosote from absorbing moisture and swelling.

The best things about Homosote is that it can be cut easly with a sharp box knife and it isn't too heavy. I suggest not using power saws to cut Homosote as it will dull your saw blades extreemly fast causeing you saw to tear the Homosote rather than cut it. I highly reccomend the use of Carbide tiped saw blades and a table saw for cutting it.

Another thing I like about Homosote is it deadens sound much better then plywood alone but ,not completely.

Do Not use Homosote as the main base material because, It's a Flexable Paper insulation product, and it has very littie ability of staying ridged and flat on its own. It requires suport under its entire body with plywood and a 12 to 16 inch square grid of 1X4 Fir or Pine.

1/2 inch plywood is strong when left in its full 4X8 sheets with support framing and a 16 inch square grid of 1x4 inch fir or pine under it and firmly attached or glued to the Grid. When 1/2 inch plywood is used in cookie cutter fasion it will required you to have a support riser at least every 12 inches or the plywood will flex and give your railroad a roller coaster effect which isn't wanted. This type cookie cutter roadbed base support has little or no sound dampening properties and requires a layer of Homosote or Cork roadbed layer to help deadin sound vibrations but is quieter if both Homosote and cork is used.

I have never used Foam of any kind or thickness so I can't give any opinion on what to use in the foam family.

From what I'm experencing using Masonite cut in 7/8 wide strips and stood on edge to make spline road bed once the glue is dry it is a much stronger and quieter then any product I have ever used before I am using 1/2 in plywood with 1/2 homosote glued on top for yards and town areas. 

Personally everybody needs to expermint with most of the available products to find out which works best for them. I have read all the posts about Track road bed and there are good bad views on every product out there. It all depends on each individuals needs and money on hand as to which one is for you.

HOMASOTE IN ONTARIO CANADA

Hello;

         Iam new to this site and a real newbie,except that Ive been buying-up model railroad stock for about twenty or so years and am only now about start my first layout.If there is any one in ONT.CANADA  that needs homasote you can still buy it here.

A 4x8 sheet was about 25.00 CAD. last fall

        Hope this may be of some help ,I have seen this used in number of areas on layouts with a plwood sub-base and to me seemed to be a cost effective way to go.Only my oppion,

                                                                            DRRON946