Hello folks,
I have begun constructing benchwork for my 4X8 layout. I would like to know how large a span will be needed to support 2" extruded foam. I was thinking of 18". Will this be enough? (There is no pluwood under the foam.)
Thank s,
BB
Standard construction supports of 16" OC should be fine. Of course, you really only need two 1x4 boards running down the long axis of the foam for support. Shok absorption along the edges of the foam will require some sort of wood sheathing (1/8" Masonite or 1/4" Lauan should do).
I’m using 16-inch spacing, and no plywood. My frame is 1x4, and I use 1x3 supports for the foam, aligned with the bottom of the frame. I put 1x2 supports in a few places around the outer frame so I could have support for the foam while still having it inside the frame. That way the frame protects the foam’s edges. I glue it on with Liquid Nails for Projects.
I’m sure 18 inches would work, too. 2-inch foam is pretty stiff and doesn’t sag.
Bruce;
18" is plenty, increasing the spacing to five supports over the 8ft length is more than enough.
As mentioned above, make sure you protect the edges all the way around. I am using 7/16" OSB underneath, and around the edges, no other supports. I used the OSB because I had it left over from another project. If I had to purchase new stuff, it would have been the thinnest, cheapest stuff I could find.
I’m using 1x3 support bracers every 18" for my extruded foam base, and it’s worked out just fine. Also, if you layer the foam for scenery, each layer tends to strengthen the foam extremely well. I’m amazed at how strong the foam actually is. One thing, though, if you run out of extruded foam (it’s hard to find here in California any more) and have to resort to the 2" beaded foam insulation, you’ll need to change the bracing to 12" or even 10" spacing, as the beaded foam has only about 1/3 the tensile strength of the extruded. But either way, the foam bed allows you to use much lighter bracing than if you were using plywood. I find it much easier to work with, also.
Good luck.
Tom [:D]
I built my 2’ wide sections with 16" spacing for the crosspieces. I’m pretty confident I could use 24" spacing instead and it would still be plenty strong. Probably even 1x3’s instead of 1x4’s - I have a lot more benchwork to build so for the next pase I may experiment a little.
The problem with 18" centers, it doesn;t come out evenly over an 8’ long sectiion. But if you aren’t making sections… My idea is that if I ever move, I cna cut through the track and roadbed at each section joint, unbolt them all, stack them up,a nd go. Probably wishful thinking, because I will never have a basement with this same shape anyway.
–Randy
There is no way to attach under table switch machines such as Tortise, or for that matter any other under table devices to foam. Use the foam but support it with at least 3/8" plywood min, thickness, 1/2" is better, then you have more support for under table wiring and switch machines. You can then support it with a 2 foot grid spacing. If nothing is under the table, 16 inch centers will work.
Mounting them underneath is so old-fashioned [:D][:D][:D]
Check my web site. I don’t use plywood, and I’m not going to start.
–Randy
I am using 3/4" plywood as the base and 2" foam on top of that for easy scenery and layou construction. When you consider the value of what you will have on TOP of the table/benchwork, “why” not spend the few extra bucks and make yopur layout bullet proof for strength. Yes, there are those that will say that 3/4", even 1/2" plywood is overkill, but after 66 years, I have learned to error on the side odfstrength and security for a few extra bucks “once”. You will always have the plywood, lean on the foam with no support underneith in “that” area just once too hard, and you will have your answer.
My [2c] worth,
BTW, nice website Randy, I like what you have done !!!
Absolutely untrue. With a little ingenuity, you can do ANYTHING with foam that you can with “traditional” layout construction techniques. Model Railroader has run at least three articles in the past ten years about mounting switch throws (manual and automatic) to foam-based layouts, and they work. I’ve operated on Bill Darnaby’s Maumee Route layout, and all his homemade, hand throw switch levers are glued to his 2" foam, NO PLYWOOD, layout. Some have been in and working for ten years without a single failure. And with Tortise machines, all you need to do is mount the motor to the underside of the switch, carve out a hole in the foam to accept the switch machine, and drop it into place.
Again, wholly untrue. Some of the largest operating layouts in the country (see above) are built out of 2" foam base with NO underlayment plywood, and with only 16" OC 1x3 supports. If you DO decide to go with a wood underlayment (not a bad idea in my judgement) you only need 1/4" Lauan plywood (door veneer; the cheapest plywood on the market). My own three level layout is built out of 1/4" ply and 2" foam, supported off the layout room’s studwalls with metal shelf brackets. It’s been up for three years, and I have had zero benchwork problems.
If anyone’s interested in seeing pics of my layout under construction, email me offlist and I’ll be more than happy to send ya a few (I’m too cheap & lazy to post them online!)
I’m with grayfox. I’m currently building a new layout using 3/4" plywood. Why? I want it strong enough so that if someone lays across it it won’t cave in, AND any vertical easements will become automatic as you cannot bend the stuff all that easily. My benchwork is also 2X4 on 18" centers. I can crawl around on it without damaging it. Overkill, maybe, unless someone by “accident” down the road puts their weight on it. Picture some dufus (me) falling through the benchwork. Now picture yourself falling through your benchwork. Get the idea? Unless you’re going to have a very narrow layout, I’d put down some plywood.
You can easily span long distances with the foam, BUT the foam cannot support much weight before it starts to give. When you look at all the cost of what you’ll put on top of the foam, as well as the value of your time, plywood is CHEAP.
Mark in Utah
I’m 6’2" and weigh 225. I walk and knee-crawl all over the lower level of my layout, which is a 2x2 box frame with 24" centers, 1/4" pine plywood and 2" foam. I’ve been doing this since the lower level was put in three years ago. It’s more than strong enough for ANY modelling purposes, besides O and larger live steam.
Personally, I’d WANT vertical easements to be flexible, so you can build them as units homogenous with the rest of the benchwork. I’ve got one area on my layout that has an area of track dipping below the main grade. I cookie cuttered it out of the pre-existing 1/4" Lauan plywood and 2" foam, and just bent in to the desired grade. With it flexing in an easy, natural way, it was easy to eliminate the REAL problem with vertical transitions, that of the sudden introduction of the grade. Instead of a harshly delineated line (which can cause havoc with derailments if it’s done wrong) I’ve got a nice gentle slope to the grade.
This is a HUGE waste, and I would strongly recommend to any newbie to NOT waste the time, effort or money on this sort of overkill. You’ve just built a loft structure, not a layout!
Once you factor in what you’ve just built (3/4 BC ply, 2x4x8’ B or C grade studs, a 5lb box of screws, etc) versus minimalist layout technique (foam, 1/4" Lauan sheets, 2x2 legs, 1x2 leg supports, 1lb box of screws, 3-5 $1 tubes of caulk) you’ll find that you could have saved a pile of dough by engineering the layout more carefully, versus brute forcing it.
[quote]
QUOTE:
I can crawl
The problem with using framing lumber for benchwork(crossmembers) besides major overkill and waste as compared to ripped quality 3/4" ply or pine 1x4s, is if one of the 2xs wants to bow, twist or warp it will usually take everything with it. If you still want to deck framing lumber w 1/2 or 3/4 ply, go for it but I feel it is too much. I personally prefer pine L girder and pine crossmembers for the majority of benchwork. Pine spline on risers, but this is my overkill.
Bob K.
I don’t know how Dow rates their foam, but the various Owens-Corning extruded foam products have product names that reference their compression stength in PSI. The common stuff I get at my Home Depot is FOmular-250, which is 250 psi compression strength - true this is against a solid immovable object, not unsupported. I’ve leaned on mine while trying to get a straight down view to align tracks, and it doesn’t give. If I lean on my elbows it does. There is the next product up, either 350 or 450. The local HD doesn;t carry it, and it is likely to be very expensive. It’s designed to insulate the OUTSIDE of a foundation and withstand the force of the backfill. If you could get 175 pounds on a 18" span of the 250, the better one would take well over 200 pounds.
–Randy
Hi Randy;
I just bought some foam at Menards’ this afternoon; Dow Fomular 150, 2" thick. They also stock 250 in 2" thick, which he said was for under and on the outside of concrete foundations and walls.
Ray seems to be the only one here with any sort of engineering knowledge. I am a Registered Professional Mechanical Engineer. Strength and stiffness of anything like a table top or similar is proportional to the thickness of the material cubed. SO if you double the thickness, the strength and stiffness will increase by a factor of 8. Thus 2" foam is EIGHT times as strong as 1" foam.
If you insist on laminating something under 2" of foam, use the cheapest materials you can get. I used 7/16" OSB on my last model railroad project because it was here left over from some other project. If I had to buy new material, it would have been the thinnest and cheapest plywood Menards’ had.
3/4" plywood, supported on 19.2" on center is sufficient for flooring in a house - and meets code - with people, refrigerators, beds, etc. Get real, you are not going to have a dance party
No, your not going to dance on it, but you have a lot of time invested, and $$$ with all the track and equipment and structures. If money is an issue with your budget, you have to go with what you can afford, but if you can afford plywood, why not? I have my wife’s dept 56 Christmas display on 6 4x4 3/4" panels. As this layout is against the walls, I need to crawl up on these panels to run HO gauge track, set houses in place, trees, etc at the far reaches of the universe. The plywood does not flex at all to my 185#. The spacing of the supports is 4’ where the panels join.
I am not trying to convince anyone that this method is the last statement in layout construction, it is “me”, I like things made strong, if I ever “have” to crawl up on the layout, granted, this should not happen often, I do not want to worry about it in “my” mind. Yes, plywood is not cheap, it is $27 for 3/4" 4x8 sheet, but I will buy it once, and never worry about it again…can I say that for foam with no under layer base? NO…sooner or later, there will be an accident, maybe not by you, but a friend or a curious youngster. I have seen it happen.
Anyone bother to read the 05/05 Model Railroader, p.66 - 69 ??? “Weed-Tree Splinters” are probably part of a previous age & steel studs etc. are now of the 21st. century. For those who slept thru it: “Benchwork frames made with steel tracks and studs … 1/4” plywood screwed to top of frame … 2" foam insulation board scenery layer … 1/8" hardboard fascia."
Though I may not know much
(12 year old newbie)
isn’t it reasonable to say that both methods are okay ways for benchwork
Plywood is a proven technique, but is becoming expensive and has its inherit problems
I use plywood for my 4x8 and havent had problems(except for a bloody lip)
Extruded foam is a new, less proven (not to say that i don’t think it would work) technique that has promise but questions of ability to carry weight.
Also, hasn’t steel been becoming more expensive?(though i probably wouldnt know)
-Siddharth
where do you get the 2" foam. All I can find at lowes is the 1/2" stuff