In Linn Wescott’s bench work book he says to raise the flat top up on 2" risers attatched to the joists to allow clearance for a saber saw blade when doing cookie cutter contruction with plywood. Are there advantages to doing this or an absolute need to do this if my flat ply, lying on 1X4" moveable joists already gives me 2"+ clearance from accidentally cutting L girders? I cookie cut on my previous unfinished layout by merely moving joists out of the way as I saber sawed and then back behind the finished cuts. If I add the 2" risers now, I’ll have to lower the benchwork lst which is doable but rather not if it’s not necessary… If I don’t raise the flat top areas up on risers to start with, am I limiting scenicing down the road in any way? I guess gullies, valleys, rivers, etc. would have to cut into some joists or are they angled/moved out the way easily enough in all cases? It would seem that I’d have bridges crossing any lowered areas anyway so they’d already be up on risers and abutments. How have you done it? I have to decide which path to take in the next few days … Thanks!
I think you have laid it the options and reasons pretty well. It’s easier to cut the plywood while it’s on the joists - more support under the plywood makes for lesss vibration and smoother cutting with the saber saw for somebody of limited skills like me.
But once the cutting is done, it’s easier to build the scenery if the roadbed is up on risers. If risers are not universally used, the scenery has to come up to roadbed level at every joist, which is going to be a major obstacle to realistic terraforming. Risers and cleats are usually kept under the plywood, with the cleats only extending beyond where scenery support was specifically desired. By keeping risers and cleats under the plywood, scenery can drop to top of joists (or lower in between joists) whenever or wherever desired or needed. At least that’s the way I did my cookie cutter.
An unmentioned advantage of having the plywood on risers is giving easily accessed space above the joists, but below the roadbed, to put the wiring and any mechanical linkages such as turnout throws. When I did lay my plywood directly on the joists, I ended up drill holes in the joists and running the wires through the holes. Even then, wires would occasionally get snagged while reaching or working under the layout.
Another thought: before you cut or adjust your legs downward, try the layout at the higher level. You may like it higher than originally planned. I did. But if you don’t, lowering the layout with L girder framing is not all that difficult. I found L girder to be the best and most flexible benchwork solution provided benchwork “thickness” and weight would not be issues.
my thoughts and experiences, your choices
Fred W
As far as cutting the plywood, it is easy to place a couple of 2x4s along the plywood sides so that the saber saw avoids the framework. Risers can be easily added later to set the plywood on its permanent grades, and the risers will be located more accurately under the roadbed.
Regardless, the base level of the plywood should be at least an inch or two above the framework. This will allow for below-track scenery effects such as ditches, shallow gulches/streams, culverts, and little bridges. That will make your layout much more interesting.
Mark
Thank you guys. I need to clarify what you’re saying a bit though…to be sure I’m understanding you correctly… It sounds like you both feel it’s ok to cut the roadbed sections out of the flat plywood top, while it’s resting on the original joists (as long as I move them and don’t cut through any of them), and simply add my risers under the cut out sub roadbed as I go? It’s not ESSENTIAL to raise the entire flat top on riser first as long as I allow for saw blade length below the ply. (As in Wescott’s/Kalmbach book). My joists can always be moved later if I should decide to run a creek or river, etc. below the zero elevation flat ply areas, yes? Thanks in advance for giving me a reality check to see if I’m understanding you correctly. Fred, I have my lower bench at 48" and my upper level (on future risers) will be at 56" just where I want it. If I need to lower the benchwork, I can do that by screwing the height adjustment bolts in 2" and then adding the 2" risers to raise the ply flat top. I was just hoping that wouldn’t be necessary.
I think that Linn was concerned about cutting the joists, or having the joists interfere with cutting, much more so than cutting the L girders. IIRC, he advocated 1 x 4 joists (gross overkill!!) which are 'way deeper than any saber saw blade.
The nice thing about using risers is the freedom to use anything for joists - mis-matched, odd-height and even split-top wood can be used. My own choice is steel, but that’s a climate thing.
You might consider making your risers out of the smallest available steel stud material. It cuts easily, screws to risers and subgrade with really small screws, and screwing flanges for the roadbed can be snipped and bent in seconds (no separate cleats.) Try it, you may like it.
Chuck (modeling Central Japan in Septmeber, 1964)
Yes, it is perfectly OK to cut the plywood while it is fastened to the joists - as long as you move each one before you cut it. In fact, the plywood is typically better supported on the joists, making for less vibration and hassle while cutting the plywood.
(Quote) My joists can always be moved later if I should decide to run a creek or river, etc. below the zero elevation flat ply areas, yes? Thanks in advance for giving me a reality check to see if I’m understanding you correctly. Fred, I have my lower bench at 48" and my upper level (on future risers) will be at 56" just where I want it. If I need to lower the benchwork, I can do that by screwing the height adjustment bolts in 2" and then adding the 2" risers to raise the ply flat top. (End Quote)
I am concerned that you seem to be describing a second deck at 56" in the quoted portion. 8" separation between decks isn’t enough. You can’t reach into the lower deck easily, and you probably won’t be able to see much of it, either. Planning multiple decks is fraught with compromises over access, overlaps, elevations, lighting, and viewing angles. Usually, one ends up at at least 12" rail to rail separation between decks, with 18" even better if the resulting deck heights are acceptable. Almost a mandatory part of multi-deck construction is minimizing the thickness of the upper deck benchwork - a situation for which unmodified L-girder is not well-suited.
OTOH, if you are talking about a track elevated 8", but on the same underlying benchwork (or deck), that’s a different story. Whether track ranging from 48" to 56" is optimum for you is a personal decision. As you mentioned, the low/high points of the range are adjusted by where the legs attach to the girders/joists and/or by trimming or replacing the legs.
Whether the lowest elevation subroadbed is left directly on the joists, or is elevated by risers, is a personal decision. Leaving the lowest plywood on the joists will limit your terrain flexibility considerably when
Thanks VERY much Fred and Mark. I thought I was understanding you both, correctly but wanted to be sure… My higher elevation IS just a raised area with a grade up to it, not a 2nd double deck(ed) layout. Obviously, I’m having enough of a learning experience with a single deck layout at this point! It’s a good thing Tony Koester’s new book didn’t come out earlier though, or I would have been sorely tempted! It’s one of the best written and illustrated Kalmbach books ever. Anyway, I’m heavily leaning towards keeping my zero elevation on the joist tops, and dropping down in any joist areas later, that I didn’t initially anticipate needed a river bed or valley. My room is so small, that it’s going to require a lot of climbing atop the benchwork to saw and I think I’d appreciate the additional support resting directly on the joists for now. I guess I’ll have to leave a bit of extra slack in the buss and feeder wiring until I’m sure how the terrain will end up. If it looks like it’ll simplify running wire and making permanent connections I may raise the flat areas on risers too. Thanks for the 2X4 tip. So simple I didn’t think of it 
Thanks again guys. I’ll consider both approaches and make a decision after Thanksgiving. Just glad to know it’s not going to be an ultimate “deal breaker” to do it one way and not the other. Cheers!
You could look into using Woodland Scenics subterrain / risers system. Be easier to raise the track a couple of inches rather than do all that cutting. [;)]