A little bit ago someone posted here that they felt we were overbuilding our bench work.
My n scale benchwork was built using 1’X3"common white board with 2"x2" furring strips as legs…inexpensive, but you have to cherry pick your pieces in order to get straight pieces.
I let the lumber aclimate to the basement for 6 months…6 impatient months, then coated them with a floor grade poly that I mixed a 2 part walnut and one part cherry wood stain into. This was all material we had left after building our house (ourselves!) The stain and poly were left over from building a dual trestle table out of red oak for the dining room…good size, seats 14 with ease and weighs a ton!
I used Titebond wood glue and countersunk #8 2 inch wood screws to hold things together. The stringers were set 16"oc.
For the top, I used Dow solid poly insulation boards, 1 and 1/2 inch, and appropriate adhesive, let that cure for 48 hours.
The bench work is quite sturdy. I think our op on overbuilding may be on to something.
I built a 4’x8’ nscale layout using four 8 foot long 1"x2" pine to support a 4x8 2" thick foam board. The result is not strong enough for me to stand on, but it is plenty strong enough not to sag. The facia I glued to the edges also provides depth and therefore strength. Prior to adding plaster scenery, the whole layout weighed about 25lbs. (11 Kg.).
Better to overbuild rather than the opposite. Benchwork that eventually twists, sags, or fails in any other way will forever be a source of frustration and regret.
The original section of my HO layout was 5x12 feet. It was built with a 1x4 frame using 1x3 crosspieces. The subroadbed was 2 inch pink foam. It was simple and worked very well. I stained and polyurethaned the outer wood surfaces and that provided a suitable fascia. I used 2x3 lumber for the first legs, reducing that to 2x2 for subsequent sections.
Cabinet grade 3/4" birch plywood, ripped to “1x4 dimentions” was the base for my current and previous layout framing. Desipte being garage-stored in unfriendly climates for several years, it has remained straight and true. For shorter spans, I used similar grade pine plywood.
Back in the day, the cost was about the same as high-grade stick lumber; not sure about this now.
The adapted plan can be configured as a double track figure eight with two trains running in opposite directions.
The adapted plan enables local switching operations on sidings while other trains run continuously.
The adapted plan can be configured as a twisted dog-bone that crosses the river six times before traveling over the same segment of rail twice.
The adapted plan provides two variants of out-and-back originating either direction from the industries along the river.
The layout is quite far along these days. There are lots of sections to the web site with lots of pictures. My primary interest in the hobby is scenery and structures. I design and 3d print most structures and all of the lift bridges.
I did years ago. I had a 10 foot span using 10 foot long 1x4’s. The sag was slight but noticeable. I added a leg in the middle which solved the problem. I now limit my spans to 8 foot using 1x4’s.
FWIW I’ve adapted the construction specs from the NMRA HO module construction specs. 1x4 for the frame and 2x2 for the legs. (Finding straight 2x2 is always a task.) Instead of the 1/4 hex bolts specified for the legs, I have 3/8" diameter furniture levelers. (The current layout was originally built in a room that was badly out of level and I needed the bolt length to get the layout level.) One piece of my lake section is an old module from when I was in a club over 30 years ago with the new levelers installed. (Yes some of the sections and parts of sections are that old or older.) The tops are mostly plywood of various grades and thickness. Two section tops however are hollow core closet doors that are older than I am.
I live in southern California where it is almost impossible to find decent dimensional lumber. Even the kiln dried stuff you have to sort through to find a few straight pieces turns to pretzels by the time you get it home! I prefer to rip sheets of cabinet grade plywood into the benchwork framing pieces I need. Good plywood is far more stable and actually stronger than dimensional lumber. My current 10’ by 19’ double deck HO scale layout benchwork is all constructed from 1/2" plywood. The only dimensional lumber I used was several kiln dried 2x4’s I carefully picked out, let sit for a few weeks, then gradually ripped down to a true 3" width using a 4’ long rip fence on my table saw. These 2x4’s were then used to build a central backbone wall from which I double-cantilevered my peninsula decks. Fortunately, these 2x4’s have all remained straight over the last 15 years. The 2x4’s that didn’t make the cut for the backbone wall were cut up into 2x2 glue blocks used to reinforce the joints in the plywood benchwork. These allowed me to quickly erect the benchwork using wood glue and 18 gauge wire brads. The layout decks are only 3/16" plywood with supports every 16". No warping, no sagging, and the benchwork will easily stand up to someone falling and catching themself on the edge of the layout. Of course, they might not survive my wrath for their clumsiness!!!
It was not an L-girder, just plain 1x4’s. I don’t use L-girder since I use the underneath of the layout for other things. In this case I had bookcases underneath.
The whole thing is supported by two chests of drawers that are positioned about a quarter of the way in from each end.
I can load the layout down with weights and do not see sagging. Everything stays nice and level. The combination of 2" foam and 2" wood glued together is strong.
When I built this benchwork, it was open grid. 1"x3" can warp eventually so I added blocks between the 16" on centers so that stringers were attached at the perimeter but were blocked in the center.
That has the effect of adding a third joist amidships and should go a long way towards eliminating warping. It also adds quite a bit more strength. Time will tell.
With the 1 and 1/2 inch extruded hard foam, I can lean on the top with no problem, but I would not try to walk on it! It seems to be very sturdy and a lot lighter than ply.
Update - I was at the big-box home center yesterday and stopped by the lumber section. The cabinet grade 3/4" birch plywood was $84 per 4’ x 8’ sheet - which would yield 12 1x4 8 foot boards at $7 each.
The 8 foot “treated, appearance grade top choice” (this was the step below “perfect”) 1x4s were $8.87 each.
So, at least per this sample, for both quality and cost, the high grade birch plywood is the better choice over stick lumber for building benchwork.