Does the layout need a plywood / wood base under foam

To me one inch is not that thick. If I was doing that I would put something under the foam for a little extra strength. In my case if I leaned on the foam to reach something my luck I would break the foam............Paul

JD,

   IMO it's not a good idea to build your layout without some kind of secure base, it should IMO be able to with stand the weight of an adult human being.  Others may believe differently, however I have been building layout for more than 50 years now and have never had a problem.  Unless you put your layout directly on the floor use a secure base of some kind, I use 3/4 Ply wood most of the time, on every level.

PCRR/Dave

I think 1 inch is very thin and will sag and//or break without adequate support.  Modern O gauge locos are heavy.  I have a switching layout built in 2 inch foam but that is completely supported in a solid cabinet.  Only the front as about 4 inches of overhang.  

I have a small (9x6) walk around layout. The framing is 2x4s spaced 16" on center. The top is 2" thick blue foam directly on top of the frame. I have had this layout for six years with no problem. If the layout was bigger I would have put 1/2" plywood under the foam, but I can easily reach anywhere on the layout without climbing on top. The 2x4s are probably overkill but I already had them so they were "free".

Not sure I would trust the 1" foam to support my engines. The 2" is not that much more expensive, and a lot more rigid.

Given it's propensity to ignite I would avoid using foam

Surprised nobody has thought about using lightweight baraboard sold in lumber yard its dense but light should absorb sound quite well sold in lumber yards mostly for cabinet work both in half inch and three quarters 

audi posted:

Given it's propensity to ignite I would avoid using foam

Interesting.  What is the propensity of foam igniting?  Do you have any knowledge of rigid foam board igniting in the flat horizontal position?

You may never plan to crawl up on your layout, but you may have to if you can't reach every inch of your layout.  I used 13/16" B/C Plywood with a good foam roadbed for my track. The substructure is pine 2x4.  (I am not a light-weight).  I may have a little more sound reflection, but I won't have mold and mildew from paper composite board.  I gave the bottom of my plywood two coats of semi-flat white to reflect the Lights I installed under the table.  It also deters bugs from being attracted to the raw wood.  I painted the bottoms first, then flipped them over and did the tan top.   The top has two coats of light tan to reduce splinters in my backside.  Even the best heated and air-circulated basement is damp in the winter here in Cleveland.

I installed cheap LED lights to the underside of the table to help with wiring of the layout.  I wore a headlight and dragged a drill around.  I did not want to drag lighting too.  All my rolling stock is on fifty rolling Microwave/Utility tables under the layout.  I will be able to pull the tables to the center river in the layout to exchange cars, group by railroad name.  I originally had heavy metal shelves under the layout, but they were hard to move as I worked under the table.  The Sauder Microwave/Utility carts have a nice light oak finish and wheels that are very easy to move.  And here is were my progress stalled.  To be continued soon, I hope.

Nice work on the layout, John.  Your framing work looks great.  

Nicely done John

I have to agree with a previous post that 1" foam is probably not think enough...you may get away with 2" foam....I have that on top of plywood and in some areas plywood and homasote...the only issue with the foam that I have run into is screwing anything down into it...like your tracks....you may have to glue things down where you would normally use screws...as far a a fire concern mentioned above ...I don't take any kind of flame, torch or any other fire hazard any where near my layout...so for me that is not a concern....but something to consider in what tools you plan to use to scenic your layout..

wild mary posted:

audi posted:

Given it's propensity to ignite I would avoid using foam

Interesting.  What is the propensity of foam igniting?  Do you have any knowledge of rigid foam board igniting in the flat horizontal position?

I think someone posted pictures of an actual fire on foam about a month or so ago.

even if the fire doesn't start on your layout, were one to break out, your layout now becomes a fire hazard.

I, personally, would always use at least 1/2 inch plywood.

Berkshire President posted:

wild mary posted:

audi posted:

Given it's propensity to ignite I would avoid using foam

Interesting.  What is the propensity of foam igniting?  Do you have any knowledge of rigid foam board igniting in the flat horizontal position?

I think someone posted pictures of an actual fire on foam about a month or so ago.

even if the fire doesn't start on your layout, were one to break out, your layout now becomes a fire hazard.

Nick:  I'm not sure what you are getting at here....and why the need for the cartoon?  The topic is whether or not the board in question is flammable, which at least one other poster mentioned.  I merely stated that I thought someone posted pictures of an actual fire about a month or so ago.

So what, exactly, is your problem?

"Dunno" whose problem it is ... but the TOPIC is foam underlayment on a layout.

Compared to the cost of an ogauge loc., a 1/2"  plywood under a 1" foam base makes sense for structural integrity.

I've always used 3/4" ply - but on the current layout in progress, I'm using Mianne benchwork and 1/2" plywood.

Always use at least 1/2 plywood. 

Better to built it to strong and not need it, than build it too weak and break it. 

 I never plan to climb or sit on the layout.  

 

The best laid plans of mice and men.......and then there come a day when you will need to lean in on it, set too much weight on it, etc.  Some sort of support grid under the foam if it's only 1" would seem prudent.

This is 2" blue board. The torch is used to make water features. Maybe someone else has video of what happens with a torch on plywood. Everybody make there own decisions. But the risk of fire hazard, I think, is a little over stated in the model train environment.  My $.02.  TW

Berkshire President posted:

wild mary posted:

audi posted:

Given it's propensity to ignite I would avoid using foam

Interesting.  What is the propensity of foam igniting?  Do you have any knowledge of rigid foam board igniting in the flat horizontal position?

I think someone posted pictures of an actual fire on foam about a month or so ago.

even if the fire doesn't start on your layout, were one to break out, your layout now becomes a fire hazard.

I'm no fire catalyst expert, but I've heard of at least a few episodes where foam was involved and only exacerbated the fire. I've always thought a layout is a high potential fire zone - a cocktail of wood, electricity, paper, plastic and cardboard), so why increase the risk by adding foam? But the weight savings does have appeal.

What if the foam board is painted - does this help mitigate it's possible likelihood to catch fire as quickly?   The reason I ask is that I am considering using it for weigh savings (2" over 1/4" plywood - for pop-outs only).   

Peter

Jamken posted:

Surprised nobody has thought about using lightweight baraboard sold in lumber yard its dense but light should absorb sound quite well sold in lumber yards mostly for cabinet work both in half inch and three quarters 

baraboard  What is this mystery material? Do you have link for it?

I think the OP left out some info causing confusion, specifically what will be under the foam, and I think a lot of folks are saying what they "think" vs what they "know". This is often the case here because people tend to fall back on what they've always done or what the various books suggest. For example, 1x4 vs 2x4 framing, 1/2" vs 3/4" plywood decking, cork vs foam vs rubber roadbed, layout height, etc.

That said, I used 1" foam a top of a 12"x12" grid of 1x3s for 2 sections that were 48"x96"/48"x72" and bolted together for my Christmas layouts for over 2 years. I chose the 12" grid because I had no prior experience with foam. I have no doubt a 16" grid would have worked just fine. What I don't know is if a 48"x96" frame with crossmembers at 16" or 24" would have worked as well because there would have been sections 16"x48" or 24"x48" not 12"x12" or 16"x16". I don't how the foam would have stood up over time to a heavy engine sitting lengthwise between the crossmembers.

I do have a 48"x48" temporary test module set up with a single crossmember in the center resulting in 2 sections that are 24"x48". I've set some heavy items on top for short periods with no problems. What I did get with my Christmas layout though was a lot of noise resonating below the layout. For that reason alone, I would not use foam again without at least a 1/2" layer of plywood and perhaps a 1/4" layer would also work.

I also have little doubt that one could build modules of any length that are 30" wide with crossmembers on 16" centers if weight is a factor and not have any problems over time. However, one does have to worry about dents. Drop something on foam and it will dent. Just moving a small building around and hitting the foam with a corner will leave a dent or scratch. I moved my sections around several times over the 2 years I had it and there are plenty of dents from when I bumped up against doorknobs, etc. These were covered by the batting I used for snow, but it's something to consider if the layout will be moved.

Is this it?  "In 1962 Baraboard (later known as Medium Density Fibreboard or MDF) was invented by a local manufacturer. IWCI began to introduce this new product to other companies that were ill-equipped for the cutting and machining of MDF components, painted MDF Cabinets, and painted MDF sheets, composite wood, and panel processing solutions at high volume."  TW

Moonman posted:

Jamken posted:

Surprised nobody has thought about using lightweight baraboard sold in lumber yard its dense but light should absorb sound quite well sold in lumber yards mostly for cabinet work both in half inch and three quarters 

baraboard  What is this mystery material? Do you have link for it?

There's a blurb in the second section in this link that says it was invented in 1962 and is now known as MDF.

I was posting at the same time as Ted.

Doubledaz, this is what my xmas layout sits on.  Sets up in less than a minute. 

DoubleDAZ posted:

Moonman posted:

Jamken posted:

Surprised nobody has thought about using lightweight baraboard sold in lumber yard its dense but light should absorb sound quite well sold in lumber yards mostly for cabinet work both in half inch and three quarters 

baraboard  What is this mystery material? Do you have link for it?

There's a blurb in the second section in this link that says it was invented in 1962 and is now known as MDF.

Thanks. I pass. Will it hold a screw? reminds me of the assemble yourself furniture with the pins and locks.

TedW posted:

Doubledaz, this is what my xmas layout sits on.  Sets up in less than a minute. 

That looks familiar only mine was 1x3s for even less weight.

Don't be afraid to use foam without plywood. My previous layout and my new one under construction uses 1x4 lumber with cross members spaced 12" apart with 1" extruded styrofoam, no plywood. The foam is more than strong enough to support O gauge trains. I climb on a chair and place one hand on the table top so I can reach 3' or more to do scenery or other work on the layout. I have had no problems with the foam sagging, breaking, cracking or anything else. You can see the foam directly on the frame in these pictures. I also used carpet padding on top of the foam for sound deadening.

P.S. I don't see the point of worrying about foam being flammable. The wooden benchwork is also flammable. Plywood is flammable. I have never heard of a layout fire because the foam caught fire all by itself.

I've got 2" foam board both with and without a layer of wood underneath. No issue with strength but the noise is much greater on the section of the layout without the layer of wood. Foam acts like a drum head.