Trains.com

Subscriber & Member Login

Login, or register today to interact in our online community, comment on articles, receive our newsletter, manage your account online and more!

1/4 inch ply under foam insulation board, n scale...doable?

16539 views
30 replies
1 rating 2 rating 3 rating 4 rating 5 rating
  • Member since
    August 2022
  • From: New England (Cape Cod)
  • 128 posts
1/4 inch ply under foam insulation board, n scale...doable?
Posted by DonRicardo on Thursday, August 18, 2022 7:33 PM

I am building a n scale 40x84 layout, and am considering using 1/4 inch ply under 2 inch pink insulation board. Is this doable or a bad idea?

 

  • Member since
    January 2011
  • 892 posts
Posted by PennCentral99 on Thursday, August 18, 2022 8:41 PM

What are you using for the benchwork? 1"x3" benchwork, with cross support, and 2" foam is ample for a layout. Why waste time, money and effort adding an unnecessary layer of 1/4" plywood?

Inspired by Addiction

See more on my YouTube Channel

  • Member since
    September 2011
  • 6,398 posts
Posted by MidlandMike on Thursday, August 18, 2022 9:37 PM

I would put in the 1/4" plywood, especially if you cut into the 2" foam for below track scenery.  It will also keep your benchwork frame square.

  • Member since
    July 2006
  • From: 4610 Metre's North of the Fortyninth on the left coast of Canada
  • 9,229 posts
Posted by BATMAN on Thursday, August 18, 2022 10:24 PM

Working through 2" foam and ply is a real pain. I am in the foam only camp with 2".

 

Brent

"All of the world's problems are the result of the difference between how we think and how the world works."

  • Member since
    March 2012
  • 1,134 posts
Posted by PC101 on Friday, August 19, 2022 12:09 AM

Would the 1/4'' plywood give you something solid to screw mount a switch machine to it?

Although you would need to route out the 2'' foam so the metal rod of the switch machine will have travel to move the throw bar.

  • Member since
    September 2003
  • From: Omaha, NE
  • 10,614 posts
Posted by dehusman on Friday, August 19, 2022 8:45 AM

I would be afraid the 1/4" ply would tend to warp the foam unless it was securely attached to the 1x3 underframe.

Dave H. Painted side goes up. My website : wnbranch.com

  • Member since
    September 2003
  • From: Southeast Texas
  • 5,435 posts
Posted by mobilman44 on Friday, August 19, 2022 8:53 AM

For the size of your layout, 1/4 inch would be fine.  It never hurts to have something solid under the foam to prevent sagging or breakage - like when a visitor presses down on it, etc. (you get the idea). 

 

ENJOY  !

 

Mobilman44

 

Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central 

  • Member since
    July 2006
  • From: 4610 Metre's North of the Fortyninth on the left coast of Canada
  • 9,229 posts
Posted by BATMAN on Friday, August 19, 2022 9:35 AM

PC101
Would the 1/4'' plywood give you something solid to screw mount a switch machine to it?

Just glue a small square of 1/4" ply to the foam under the T/O.

Brent

"All of the world's problems are the result of the difference between how we think and how the world works."

  • Member since
    December 2006
  • 121 posts
Posted by gerhard_k on Friday, August 19, 2022 11:37 AM

[quote user="BATMAN"]Working through 2" foam and ply is a real pain. I am in the foam only camp with 2".

@Batman - My plan is to build similarly to how you do. But - How do you handle the track transitions from roadbed-flat-on-the-foam to the cookie-cutter uphill sections, avoiding vertical kinks? Do you sink the roadbed into the foam for a distance, attaching it through the foam to the wood below, or ...? It looks like your risers go through a hole in the foam to reach down to the wood frame, right? 
I'm getting past the track planning stage to how am I actually gonna build this - seems like a lot of fundamental architecture decisions to be made. 
 
Thanks for any tips, from others too - Gerhard 
  • Member since
    July 2006
  • From: 4610 Metre's North of the Fortyninth on the left coast of Canada
  • 9,229 posts
Posted by BATMAN on Friday, August 19, 2022 1:38 PM

gerhard_k
It looks like your risers go through a hole in the foam to reach down to the wood frame, right? 

Right.

Yes, I just lower the roadbed into the foam to start an incline or to get the track down to the foam for yard situations.

The ply you see in this pic is the only spot that has ply under the foam. It is 1/2" and I put 1-1/2" foam on top of it so it is level with the 2". I did it for structural reasons for the curved end of the benchwork and that is where the TT and RH go.

 

 

 

To lower the cork into the foam I just score it in seconds using a ruler in 1/4" squares which then break off easily. I mark the Exacto knife with a marker to show how deep to cut and then cut down on an angle until I hit the depth as shown on the knife. I put caulk in the trench as it works as a great leveler.

 

 

 

 

Brent

"All of the world's problems are the result of the difference between how we think and how the world works."

  • Member since
    May 2005
  • From: Riverside,Ca.
  • 1,127 posts
Posted by spidge on Sunday, August 21, 2022 9:24 AM

I have built modules with and without the plywood. The span between supports is important. I do have some mechanical under table turnout controls, blue point and bull frog, mounted on a three inch piece of ply, and that assembly mounted to the foam with glue and long screws for a bit of added stabillity. These have never failed and are still reliable after 10 years and moving the modules often. Since I am in Comifornia the 2" stuff is hard to find but I can get 1". So I added some good quality bircth 1/4" ply from Ganahl Lumber and it works great. I can screw things in whereever I want without adding extra supports. Ganahl's has some great lumber at a higher price point but the stabillity is worth the expense in my opinion. 
I hope that helps. There is no best way but rather what you can make work and am happy with.

John

  • Member since
    August 2022
  • From: New England (Cape Cod)
  • 128 posts
Posted by DonRicardo on Sunday, August 21, 2022 10:10 AM

1x3 open grid spaced 16" on center. Since I like having some space to catch derailments if they occur, I decided to go 48x96, with 3 and 1/2 inch borders as a minimum. That will also give added space for larger radius curves.

I am now thinking foam with cork roadbeds, but will use 1" foam glued on top of a second 1"foam and sandwich the wiring between the two layers, I like the cork because it can be sanded smooth.

 

  • Member since
    January 2011
  • 892 posts
Posted by PennCentral99 on Sunday, August 21, 2022 11:11 PM

DonRicardo

but will use 1" foam glued on top of a second 1"foam and sandwich the wiring between the two layers,

I don't like that idea. You need to keep your wiring accessible. Digging for it while buried in foam is not good or fun.

Drill holes in the 1"x3" cross supports and run the wiring through the holes.

Inspired by Addiction

See more on my YouTube Channel

  • Member since
    December 2006
  • 121 posts
Posted by gerhard_k on Monday, August 22, 2022 10:34 AM

Brent - Thanks for taking the time for such a detailed reply with the photos. It's always a bit scary the first time you actually do something, no matter how much you've read on the 'net! This will definitely improve my confidence, and I'm sure it will help others too. 

  • Member since
    February 2018
  • From: Flyover Country
  • 5,407 posts
Posted by York1 on Monday, August 22, 2022 10:54 AM

gerhard_k
Brent - Thanks for taking the time for such a detailed reply with the photos. It's always a bit scary the first time you actually do something, no matter how much you've read on the 'net! This will definitely improve my confidence, and I'm sure it will help others too. 

I also used this method after getting advice from Brent.  I also had never attempted something like this.  It was easy and worked well.  

York1 John       

  • Member since
    September 2014
  • From: 10,430’ (3,179 m)
  • 2,277 posts
Posted by jjdamnit on Monday, August 22, 2022 1:02 PM

Hello All,

DonRicardo
...but will use 1" foam glued on top of a second 1" foam and sandwich the wiring between the two layers...(Underline added for emphasis.)

That's a really bad idea!

PennCentral99
I don't like that idea. You need to keep your wiring accessible. Digging for it while buried in foam is not good or fun.

I completely agree.

A primary reason for using foam as a base is the ability to carve or sculpt terrain features into the foam.

I wouldn't want to breach a feeder wire sandwiched between two pieces of foam for fear of fire.

Think "Call Before You Dig" from prototypical utility companies.

On my 4'x8' pike I have no underneath access, it sits on the spare bed in the computer/railroad/spare bedroom.

Originally, the base was 1/2-inch Medium Density Fiber Board covered with 1-inch foam.

I used 2-1/2-inch Luan plywood strips; like a facia extending up from the edge of the MDFB, for stiffening.

The MDFB was heavy and prone to sag, even with the stiffening stringers.

To upgrade the base I made an open grid 4'x8' frame of 1"x4"s with stringers on 32"x24" with 1/4-inch plywood under the 1-inch foam to replace the MDFB.

This is much lighter and stronger with limited under-pike access.

For my wiring, I cut straight "utility trenches" in the foam; 1/2-inch deep and 1/2-inch wide using a 1/2-inch wide wood chisel.

I used 1/2-inch Split Poly Loom; used for automotive wiring harnesses, press fit into the "utility trenches." 

This allowed me to paint, scenic, and ballast over the wiring while still allowing access.

When I needed to make direction changes (junctions) I used a 2-inch hole saw and cut "utility pits" in the foam, by hand.

These are covered with small buildings- -for access.

Using this method I was able to run track feeder wires in separate "utility tunnels" from turnout control, by creating parallel paths.

All these "utility tunnels" converged in a 9"X16" central "utility pit" which holds the terminal strips, Auto Reversing unit, and circuit breakers.

From the central "utility pit" to the control panel I cut five (5) "utility tunnels." These pass directly under three (3) lines of ballasted track.

Hope this helps.

"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"

  • Member since
    August 2022
  • From: New England (Cape Cod)
  • 128 posts
Posted by DonRicardo on Tuesday, August 23, 2022 7:00 PM

thaks for the replies, some foof for thought!

  • Member since
    August 2022
  • From: New England (Cape Cod)
  • 128 posts
Posted by DonRicardo on Wednesday, August 24, 2022 8:00 AM

Niiiice! Since this is a small layout, due to space restrictions, I am using manual throws and running three locos, the benchwork is 1x3, 16 inches on center.

  • Member since
    November 2002
  • From: "Steel, Steam and Thunder"Fort Wayne, Indiana
  • 1,177 posts
Posted by TheK4Kid on Wednesday, August 24, 2022 11:31 AM

Take a look at Batman's post and picture. I have a 6 ft wide by 24 ft long HO layout built almost exactly the same with 2 inch pink foam base with no problems!

Mine is totally walk around.

  • Member since
    August 2022
  • From: New England (Cape Cod)
  • 128 posts
Posted by DonRicardo on Thursday, August 25, 2022 3:25 PM

The last layout I built was plywood, that required the ply be cut and raised by adding blocks to the stringers, fot elevations. I made the terrain (mountain) with rolled up paper held by masking tape and covered with MW Scenics plaster cloth.

After seeing your benchwork, I am going to go for the 2" foam.

Do you stack the foam for elevations, or use the old rolled paper method?

 

  • Member since
    February 2008
  • 2,314 posts
Posted by kasskaboose on Thursday, August 25, 2022 4:08 PM

Count me in for just foam.  Yes, annoying if you put a small hole in it but easy to cover up with tape or larger foam piece underneath. 

It's also easier/faster to put wiring through the foam than plywood.

  • Member since
    July 2006
  • From: 4610 Metre's North of the Fortyninth on the left coast of Canada
  • 9,229 posts
Posted by BATMAN on Thursday, August 25, 2022 4:47 PM

DonRicardo
Do you stack the foam for elevations, or use the old rolled paper method?  

I am a firm believer in doing whatever turns your crank.Laugh

I have dabbled in all methods over the decades and this layout is no different. A few pics from this one.

 

 

Foam.

 

 

 

 

Were gettin there.

Brent

"All of the world's problems are the result of the difference between how we think and how the world works."

  • Member since
    July 2006
  • From: 4610 Metre's North of the Fortyninth on the left coast of Canada
  • 9,229 posts
Posted by BATMAN on Thursday, August 25, 2022 5:29 PM

TheK4Kid

Take a look at Batman's post and picture. I have a 6 ft wide by 24 ft long HO layout built almost exactly the same with 2 inch pink foam base with no problems!

Mine is totally walk around.

 

Mine is 6' x 18' and two of us carried it around the house from the garage into the train room easily. I climbed up onto it early on by putting a 2' x 18" piece of ply down on the foam and kneeled on it. There was no trace of me being up there afterward.

Brent

"All of the world's problems are the result of the difference between how we think and how the world works."

  • Member since
    August 2022
  • From: New England (Cape Cod)
  • 128 posts
Posted by DonRicardo on Thursday, August 25, 2022 6:36 PM

Wow!

The second layout I did was on two 4x8 ply, one full piece, with the second sheet cut into strips for a double "L". That was the one where I cut out the ply and installed riser blocks under for the elevations. Foam seems much easier.

When my friends would call, my wife would answer, "Oh, he's down stairs playing with his damn trains!" One day, we got off work early due to some nasty weather, and I came into the house early, no wifey, but her car was in the driveway.

Guess who was downstairs "playing" with the trains?

 

 

  • Member since
    July 2006
  • From: west coast
  • 7,583 posts
Posted by rrebell on Friday, August 26, 2022 9:28 AM

DonRicardo

The last layout I built was plywood, that required the ply be cut and raised by adding blocks to the stringers, fot elevations. I made the terrain (mountain) with rolled up paper held by masking tape and covered with MW Scenics plaster cloth.

After seeing your benchwork, I am going to go for the 2" foam.

Do you stack the foam for elevations, or use the old rolled paper method?

 

 

Get a hot wire from WS and use foam, works great and finish it off with plaster cloth, you can get the medical stuff cheap.

  • Member since
    July 2006
  • From: 4610 Metre's North of the Fortyninth on the left coast of Canada
  • 9,229 posts
Posted by BATMAN on Friday, August 26, 2022 10:58 AM

rrebell
Get a hot wire from WS and use foam, works great and finish it off with plaster cloth, you can get the medical stuff cheap.

I put plaster cloth over the cardboard strips here using old tea towels and used wire screen scraps for support elsewhere on the layout. I really like using wire screen that you can easily form before you apply the plaster cloth. I have boxes of expired plaster casting rolls from my wife's Vet hospital, why they expire I do not know. I will donate them to a fellow modeler at some point.

I don't see the point of putting plaster cloth over foam, I just gouged and carved, then painted. If you do want to use plaster, with the price of foam these days cardboard or wire or rolled-up paper seems like a much cheaper way to go.

I think Wayne uses a product called Durabond (SP?) I have a spot where a canyon to the floor is a perfect spot for me to try that stuff out. Also with all the renovations, I have been doing (four bathrooms so far) I have been running down to the train room with the leftover thin-set and grout after tiling and slopping it on the layout. Here you see the different colours of various grout, but it will look great once painted and had ground cover added.

Brent

"All of the world's problems are the result of the difference between how we think and how the world works."

  • Member since
    February 2018
  • From: Flyover Country
  • 5,407 posts
Posted by York1 on Friday, August 26, 2022 11:05 AM

I really like sculptamold. 

York1 John       

  • Member since
    August 2022
  • From: New England (Cape Cod)
  • 128 posts
Posted by DonRicardo on Thursday, September 15, 2022 10:17 AM

I don't care for switch machines, I use caboose manual throws. They hold the points very well.

  • Member since
    August 2022
  • From: New England (Cape Cod)
  • 128 posts
Posted by DonRicardo on Friday, October 14, 2022 1:22 PM

BATMAN

Working through 2" foam and ply is a real pain. I am in the foam only camp with 2".

Wow, foam got pricey! When using foam, to cut creek beds, or ponds and lakes, how deep must the cut be? I am doing the Saco River in NH, which is a spring moutain snow fed river, shallow, with many boulders and rocks.

 

 

  • Member since
    July 2006
  • From: 4610 Metre's North of the Fortyninth on the left coast of Canada
  • 9,229 posts
Posted by BATMAN on Friday, October 14, 2022 2:11 PM

DonRicardo
When using foam, to cut creek beds, or ponds and lakes, how deep must the cut be?

The water depth can be quite shallow but made to look deep by the way you paint it, I will let others give you examples of how they did it, or you can check out some Youtube videos.

What determines how deep you cut into the foam is determined by how high you want the banks of the lake or river. You can always glue another piece of foam to the underside in the area you want to go with a deeper cut. 

 

Brent

"All of the world's problems are the result of the difference between how we think and how the world works."

Subscriber & Member Login

Login, or register today to interact in our online community, comment on articles, receive our newsletter, manage your account online and more!

Users Online

There are no community member online

Search the Community

ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT
Model Railroader Newsletter See all
Sign up for our FREE e-newsletter and get model railroad news in your inbox!