A deflection of 1/32 is a change of over .030. And people wonder why their trains break apart because of misaligned couplers. Run that loco over that spot in hot humid weather and cold weather for the next five years and then let’s look at the deflection.
I once acquired a used bare top 2’ x 4’ module with a top of ½" plywood. I started to lay my track on it and wondered why my turnout would not lay flat from the edge of the module… guess what, the top was bowed in and no signs of water damage on it. A perfectly square and true box had at least ¼" of deflection down in the top in the first 8" of the center length of the module. I have 5/8" supported every 24" that is sagging on a 30" wide module. Because of that I use only ¾".
Do what you want but I don’t have any warping roadbed or trains breaking apart because of undulating roadbed on my modules. It may be overkill but 4 years down the road you won’t be wishing you did use the better stuff or braced the thinner plywood every 12-14".
I used 3/4" plywood on my layout for three reasons:
Peace of mind. You’re going to invest $100’s, of not $1,000’s in materials on the layout, not to mention years of work on it, and pinch pennies for $50 or so and HOPE you didn’t cut yourself too thin? Unless you plan on moving your layout around towm weekly, go for the most robust design you think you’d ever need, and then step it up further an additional notch, and sleep comfortably for the next 30 years.
Overkill in strength. I wanted to be able to climb on the layout and not have things move. If you have track on risers ANY vertical deflection of the base will kill you, as it’ll be magnified 100 fold. I’ve found myself shimming the track with pieces of paper to get the final alignment perfect. If your layout is sagging even 0.10" you’ll see it in the running of your trains.
Sound control. Heavy boards transmit les sound than thin and lightweight boards. If you want a quiet layout you generally need to build a solid layout.
Mark, Thanks for reminding me about overkill. I usually do exactly that, overkill most everything such as pulling a 24 ft, 5,000 lb camper with a 1 ton, Ford F350 4x4 dually when a standard 1/2 ton would suffice.
I suppose the difference in the cost clouded my judgement. I believe 1/2" would “suffice” but I’d be wondering whether I did the right thing or not.
Now let’s look at the downside of oversized materials in construction:
Cutting. You have to cut all that overly-thick plywood. 3/4-inch plywood is much harder to cut than 1/2-inch plywood, meaning more dollars wasted on worn out saw blades, and time wasted on making the cuts, since it takes longer to cut the thicker material. If you’re building table tops, that’s not a consideration, but it you’re using the cookie-cutter moethod or cutting roadbed strips to fit, extra time will start to add up.
Weight. One average-strength man can handle a sheet or 1/2 plywood without a whole lot of grunting and straining. He can not easily handle a 3/4" sheet of plywood. It can be done, of course, but an arm in a sling from a strained elbow, one week in bed because of strained back, or damaged equipment (perhaps including locos, rolling stock and structures) because you couldn’t hold onto the plywood and wound up dropping it onto the layout will add a whole lot to your model railroading fun, won’t it? Simple to just get a friend to help lift the plywood sheet to the table to cut it or install it or whatever, but now you’re working around someone else’s schedule along with your own.
Cost. If you’re building a layout larger than 5X10 feet or so, the cost of the over-thick plywood will begin to add up. $50 extra will buy you maybe three or four sheets of 3/4" plywood instead of 1/2" plywood. If you layout will wind up using more than that, you’ll wind up wasting even more money.
Peace of Mind. Maybe this applies to me only because I’m a structural / mechanical engineer, but my peace of mind comes from knowing I’ve done the job right, not from building airplanes out of lead sheeting, so to speak. Because of my background I know I can use the lighter material and have a sound structure. But without being a structural engineer, maybe that doesn’t apply.
I’ve always had good experiences with 3/8" plywood. I like to use supports at least every 12 inches, and my layouts are around-the-wall types were the benchwork never exceeds 24" depth.
Most modelers massively overbuild their benchwork. I did that too but quickly realised that for my style of layout I didn’t need to. My first layouts were built like a tank and I had a terrible time building them and taking them apart later. And as said by Brunton, overbuilding results in difficult handling, excessive weight and you pay too much. Lumber and plywood nowadays is awfully expensive, and I’ve chucked away a fortune in wood when I had to move or made changes to the layout. My benchwork now is much more economical yet still very strong.
HO scale trains are not that heavy and if there is a need to climb onto the benchwork, than the design needs a re-evaluation. Maybe add an access opening or something similar to improve access.
Nowadays I don’t even use plywood anymore, just the blue/pink extruded foam on top of L-girder.
thicker sub means less l girder support needed( longer spans) but cost for 3/4 over 1/2 is also important. what are you putting on the sub… cork??? homasote? poly??? all those will be a factor. and it still comes down to personal preference and cost
Hello I’m kind of new myself but I have learned a few things. 1/2 inch is right about what you want. 3/4 inch is a bit thick ,makes for a pain when wiring. You also dont want it tobe to heavy if you decide to make it sectional for those unexpected moves.
I’d go with the half inch, with supports every 16"-24". I did see someone mention laminating two 3/8" pieces on turns. I plan on using 1/2" on my next layout this year, on open grid/L girder type benchwork. As long as supports and risers are spaced appropiately, things should be fine. 1/2" is easier to use for compensating grades as well.
We are working on a club layout in HO and have used 3/4 inch MDF. It is a little heavy but very stable. The cuts are very crisp with no jagged edges. Perhaps a little expensive, but we have found it to be worth the difference.
The method of construction is your determining factor. The average hollow core door is plenty strong enough to serve as benchwork, yet its constructed with 1/8" plywood on paper. Ahhh, the wonders of torsion box engineering. [:)] Since your construction method is already determined, all that’s left to decide is the span, etc, etc, as others have discussed.
I’ll expand on one other consideration that’s been alluded to, 3 ply vs. 5 ply. Additional plys generally mean greater stability, and with the thin plywoods, greater strength. If you’re looking for maximum stability (a very good thing), then go for marine grade Baltic Birch. 1/2" BB (actually 12mm) is 9 ply and very stable. Not cheap, but good. And strong.
Wrong, error, incorrect information. (Anybody have a smiley of the robot from Lost In Space?) Generally speaking, plywood is not stronger than solid wood, it is more stable. Furthermore, as a man made product, it is more amenable to forming into different structural shapes, especially at a lower cost than solid wood. Plywood can be strong enough (in engineered shapes) for these applications, and in fact can replace steel. Does that mean its stronger than steel? Do a quick search on any woodworking site regarding shelf spans and the characteristics of solid wood vs. sheet goods will be revealed.
I used 3/8 plywood on my HO layout and put 1 inch blue foamboard over that. Underneath, I used 1 X 4’s for framing on 16 inch centers. I lightly glued and screwed the wood parts. I can walk on it anywhere and I weigh 230#.
On my 6 inch wide, 2% mountain grades, I used 1/2inch foam over home made foam risers. If I add cookie cutter grades they will be 3/8 ply with supports about every 10 inches using a 6 inch width. You could probably even use foam for supports. The idea is not so much to hold a lot of weight, but rather to keep the plywood from warping.
Good quality plywood is surprisingly strong, but to keep it flat you must have adequate support at fairly close intervals.
We’re currently working on our forty-ninth or fiftieth layout project, some of them as large as seven thousand square feet. Except in extreme circumstances, we have never used any plywood over one-half inch for platform tops or roadbed. If we have any “secrets” about how we do it they are very simple ones: never use L-girder benchwork and do use very well supported sectional platforms.
After using high quality dimensional lumber for framing for many years, we have switched to seven-ply three quarter inch plywood for framing and one-half inch for platform tops. Depending on the project we will use either a very well supported plywood cookie-cutter technique or foam trackbed raised on custom cut foam risers. Forget twenty inch support centers on cookie cutter construction, wood is cheap at any price—repairing a mistake isn’t. The great thing about foam construction, besides it’s stability (if properly installed), is that the world doesn’t end at track level the way it does with a plywood surface. If you start with a plywood base topped with a two inch foam board these problems/worries practically vanish. If the landscpe we are modeling is mountianous we will move the platform base all the way down to the floor if necessary, but if that support platform isn’t there all you have is a bunch of expensive spaghetti. There is also no law that says you can’t mix the two techniques, using internal wood bracing to solidify foam costruction. Some of our larger projects have had vertical track separations of as much as five feet requiring a well supported elevated plywood trackboard skeleton to which sheet foam is attached and then liqiud two-part styrofoam is sprayed. But at the bottom of it all is the same thing—a very well built plywood platform.
Clarke, great technique and I totally agree with construction. We spend thousands of dollars, some even 10’s of thousands of dollars on rolling stock, locomotives, scenery, etc, that is constantly expanding over time, but we can’t spring for a few more bucks for 3/4" base plywood? You purchase the plywood once, spend the difference between 1/2" plywood and 3/4" plywood, and never have to worry about the base again.
Yes, it is heavier, and some people say it is too heavy to handle a full sheet to cut. Every Home Depot or Lowes in our area make the cuts for free right at the store. So forget that argument.
Good luck with your layout, send us some progress pictures when you have them…
Actually, Dick, he said “Except in extreme circumstances, we have never used any plywood over one-half inch for platform tops or roadbed.” They’ve switched from dimensional lumber to 3/4 inch plywood for the base structure (the benchwork), not the roadbed. Nobody that I know of that makes their own framework out of plywood, be it L-girder, grid or some variation of the two uses 1/2 inch plywood.
I don’t skimp on the benchwork, but I’m not going to waste my hard-earned bucks on unnecessarily heavy roadbed. Just a couple of sheets of 3/4" plywood and I’ve wasted more than enough extra cash to purchase a plastic car kit. Plus the thicker plywood makes clearance issues with lower level tracks more likely in areas where the clearance is tight already. No, I’ll stick with properly-sized roadbed and buy the extra car kits.
…“If we have any “secrets” about how we do it they are very simple ones: never use L-girder benchwork and do use very well supported sectional platforms.”
Clarke:
Thank you for your professional insider’s perspective about benchwork and platform tops. I do have one question(s) about your statement of “never use L-girder benchwork and do use very well supported sectional platforms”… Why and are you suggesting a “box like” or “multi-box like” sectional platform? What are your suggestions for section or box thickness? Suggested size of the boxes and sections? Are they squares or rectangles? Any other suggestions are greatly appreciated. And of course, I could go on ad nauseam [:)] Guess I better not! Thanks for jumping-in!
I did use 1X4 L-girders. I split ripped some of them in half down their lengths, and fashioned L-girders out of one of the 1X4’s and one of their split halves across the top. What I didn’t do was to then frame above them and add risers as some modellers seem to favour…takes up a lot of vertical space. What I did was to make a square frame of L-girders and add several joists across the long axis of the rectangles that the frames formed. Risers went to the joists as needed, and I think it turned out quite well.
I would like you to elaborate, if you will, your reason for not using “L” girder. My club is building a fairly expansive layout (50’x120’) with various divisions running at different elevations with most of the subroadbed pine spline. Some is cookie cutter and the facia wanders and curves. In my opinon and as a finish/carpenter, I feel that we have picked a construction system that works quite well.
First of all, I can’t believe this thread has gone on so long.
Second, listen to Clarke. I’ve spent 20 years in construction and what he describes is the plan I came up with for my layout. Not that it is the only way to skin a cat, as selector and others have pointed out. But, what Clarke describes is the cheapest and easiest way to get it right.
I never did get the L-girder thing. To me it seemed like a massive waste of lumber and time.
I don’t have a problem with anything else Clarke recommends, except the “Never” use “L” girder. Sectional boxed construction is actually a better choice for smaller layouts or a layout that may have to be disassembled someday.
Large layouts with 40-50’ long peninsulas having curving and wandering facias, rounded peninsula ends with up to 60" radius are actually better built w/ “L” girder or any form similar. The “L” girder arrangement can change w/ the shape and angle of the plan. Rounded corners done with the crossmembers set on a radian allows for risers to be somewhat perpendicular to the tracks subroadbead.
The supporting members of the layout are positioned inboard from the facia allowing the legs to be positioned as not to cause tripping. Crossmembers can be cut to any shape the facia needs.
Track elevation are easily set and adjusted with the use of risers.
I find that in my opinion, The pros outweigh the cons with “L” girder for the massive layout we are building.
