I purchased pressure-treated 3/4" plywood, exterior grade, to function as the flooring in my newly erected 8' X 10' garden shed two years ago. Two sheets, with the trimmed part cut up to serve as supports between the floor frames provided with the shed (the shed sits on clean gravel). The shed houses a 170 kg Toro riding mower. I think 3/4" was a sensible choice for supporting such a beast. Not for 10 kg of scenery, trackage, and an HO locomotive.
Used as sub-roadbed for C-girder (steel studs on edge, act like L girders) benchwork, quarter-inch plywood is adequate since it can be reinforced to prevent sagging. Just screw a piece of angle iron to the underside between risers.
Since the angle iron usually takes the form of cutoffs from the joists, it has little cost.
Granted that it won't support 90 kilograms of me standing on it. It doesn't have to. All it ever supports, beside itself, is a few ounces of extruded foam and flex track, and maybe as much as a pound of train between risers. Landforms are supported on risers, and simply fastened to the subgrade. Given that, I saw no need to build benchwork like the floor of an upstairs bedroom, or a deck that would support a Mosler safe.
I actually had a sheet of 3/4 EXT-DPA plywood in the stuff I moved from Tennessee to Nevada. Shortly after arrival it had cupped into a totally useless configuration. If I had gotten creative with a skilsaw I probably could have salvaged a free-form salad bowl. These days it has weed-suppression duty in my narrow, walled side yard.
Chuck (Modeling Central Japan in September, 1964 - in the dessicated desert)
fender777Don't listen to lonewolf' their must be a reason he is alone. Don't use 1/4 ply. I use only 3/4. Maybe 1/2 but never 1/4. Their is a reason 99% of Train and slot car layouts use 3/4in just to many to list. Don't skimp here.
The strength is in the type of framing plus the plywood, not just the plywood alone. My answer is based on scientific engineering fact plus my own experience, not on what sheep do. He asked if ¼" was ok and it is. If he asked if ½" is ok the answer is also yes. I've used them both and ½" is perfered but there is no need for ¾”. If he asked for sub-roadbed for L-Girder bench work then I would have recommended thicker plywood because there is no frame to support it or if he is using cookie cutter bench work where sections are cut out and the track is on risers. For those styles ½” should be fine. The roof of a house is made with only ½” plywood which is strong enough to walk on, unless it is rotten. It is supported only on the ends and in the middle with 24” centers. It has no support on the 8 foot long sides because it doesn’t need it. The wood floor of a house, if it has a wood floor (some houses have a cement slab) is ¾” plywood so it can hold really heavy objects where all of the weight is carried by only four legs. All of the weight of a refrigerator is on four tiny points the size of a quarter so it needs to be strong. Same with a pool table, a sofa or a bed. Bathtubs filled with water and hot tubs are also very heavy. An electric train is nothing compared to those objects. Why does a model train sitting on a flat table top on open grid framing need ¾” plywood?
P.S. There is a correct way to spell "there."
ATSF Guy, I just got thru running trains on the layout I have over 100 foot main line with many spurs & a yard area.
How big do you want you new layout to be? Any parts of the old one still active?
May last layout was made up of 2x8 modules with cross braces every 2'. It had 1/4" plywood and then 2" extruded foam on top. No sag. It even curvived being moved, although I will not be reusing any of it.
Even better, the plywood is truly only supported every 2' - the cross pieces are 1x3 while the longitudinal members are 1x4 so the plywood and the foam sit partially down inside the frame. Still, no sag. No, I can't stand on it, but why would I?
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
SouthPenn If I were using 1/4" plywood, I would install my bracing on 16" centers.
If I were using 1/4" plywood, I would install my bracing on 16" centers.
If I were using 1/4" plywood, I would install my bracing on 6" centers.
I have the right to remain silent. By posting here I have given up that right and accept that anything I say can and will be used as evidence to critique me.
I used plywood for framing. I mis-remembered the details and had Home Depot rip the plywood into 4" strips, lenghtwise.
http://mrr.trains.com/how-to/get-started/2011/11/benchwork-for-your-model-railroad
I had left over 1/4 luan plywood and picked up some free scraps at Home Depot then used 2" foam. Most people have responded that I didn't need the plywood base. I thought i would be installing switch machines, but haven't. You can glue bits of plywood to the bottom of the foam create a spot to screw in a switch machine.
Henry
COB Potomac & Northern
Shenandoah Valley
Mr.Beasley,You have given me something to cosider,the only drawback for me is the cost is about twice what it would be for plywood.
the old train man Mr.Beasley, What kind of bracing do you put under the foam & how would I build the 48 inch turnarounds without a sagging problem?
Mr.Beasley, What kind of bracing do you put under the foam & how would I build the 48 inch turnarounds without a sagging problem?
I built a simple box frame from wood. The outer frame is 1x4 pine.
The legs are 2x2, braced with gussets of 1/2 inch plywood (because I had it lying around.) I used 1x3 lumber for the cross rafters, spaced every 16 inches. I set the tops of the rafters 1 inch below the tops of the outer frame, thus recessing the 2-inch foam to protect it.
I used 1x2 for some cross-bracing to hold the box shape square and keep the center legs stable. This is Phase 1 of my layout. It's a 12x5 foot free-standing table on casters.
It takes an iron man to play with a toy iron horse.
I don't use plywood. My subroadbed is 2-inch pink construction foam. I can't stand on it or climb on it, but I would not do that anyway. I find it's a more forgiving base, easy to work with. I can cut out a railside ditch in minutes, or create a depression for a pond or river in an afternoon. Wiring holes are done with an awl, no need for a drill or sawdust everywhere.
These are 4' X 5' sections using 1/4" ply with one support running down the middle lenghth wise. These sections were first built over 75 years ago for Lionel trains, were used a second time for my son and are presently in use on my current layout with 2" foam on top.
Bob
Don't Ever Give Up
I've used 3/4" before and am using 1/2" on my current build (girders at 16" to 22" spacing).
I've used 1/4" on N-track modules before. It caused what I'd call the "banjo effect". Even with N-scale rolling stock, the trains cause the thin decking to vibrate and even amplify the noise. Not an entirely bad sound, but something to consider.
Robert
LINK to SNSR Blog
I don't have a deck as such, since I'm modeling a place where the scenery stands on edge. My subgrade (the part between the risers and the foam roadbed) is 1/4 inch plywood, beaten into submission with steel angle iron where necessary. Risers are roughly 16 inches on centers.
Even a country mainline will be raised to allow for proper drainage, so there should be some kind of roadbed/ballast former between the subgrade and the ties. I've carved mine from fan-fold underlayment, the stuff siding installers use under metal and vinyl siding. Using it, and using latex caulk as an adhesive, has given my quieter models stealth characteristics. The same models on plain plywood sound like the drum section of a marching band.
It isn't necessary to use the 'made for XX-scale' roadbed to get results. One bundle of fan-fold underlayment will provide enough for several scale miles of track, and the leftovers can be incorporated into landforms when you get to adding scenery.
Chuck (Modeling Central Japan in September, 1964 - with minimal forest products)
I have a 4'x8' pike constructed of 1-inch blue foam over 1/4-inch plywood on 1"x4" benchwork, spaced 33-inches with no problems.
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"
Thanks for the input.
Most layouts are over built for the weight of the trains. Most are built so tough that you could sing and dance on top of them. I’ve built layouts with ¼" plywood without any problems. Mostly people worry about sag when dealing with plywood. On a 24 inch wide grid with two foot centers and 1x4 pine on the front and back edges, ¼” plywood (fir) can easily hold 100 pounds per foot without any noticeable sagging.
Use the sag calulator to find out how much sag using different materials and thicknesses.
http://www.woodbin.com/calcs/sagulator/
1/4 inch is too thin. I would recommend at least 5/8 with 5 plys. Not too much more expensive. The 1/4 ply will have a drum effect when running the layout and be very noisy without cork under the track. Also if you want to add a lake and try to cut a hole in it later it will bounce and shake so bad all your ballast will be everywhere.
Don't skimp too much an engine cost $200 or more why try to save $10 on a sheet of plywood.
Steve
Im thinking about a new layout. I am trying to save as much money as possible. Can I use one fourth inch plywood for the decking or will I have to use thicker? Im planning to use one by fours for the cross bracing every two feet or so. Im planning on having three turn arounds with twenty two inch curves. The outside & inside will have one by fours running the length of the layout & I will use two by twos for legs, also I would like to just use ballast built up around the track & not use cork roadbed,since this is a rural railroad with one mainline, can I get by with that & still achieve realism?