A box frame is not that precision.

Unless you are making a module for amodular club where it has to fit into the layout and be dead straight with perfect 90 degree corners, it really is not that precision.  If you make it parrallel to the wall, you are fine.  If your cross members are off a little bit on the short side, use angle brackets that allow you and adjust the length.  If the cross members are too long, just cut them down a bit.

Box frame and access

I agree with Russ, a box frame can be build quite easily with the modern tools we have today. 

Besides, please rethink the access in the closet. Building that part with box frames would allow the supporting brackets to be placed in such a way that you will be able to create a quite substantially access hatch in the right lower corner and a small grab thru in the return loop. Even though most of the turnouts may be accessible from the front, all mishap that is possible will happen where you cannot reach in easily. Ask me how I know. And, think about relocating the leading turnout of the return loop towards the right bottom. This one - behind the wall- just asks for you to have screaming fits in the future if not relocated. Other than that, a very nice plan. And I envy you for that much space for your empire. All the best, mike.

The curved turnout on the entrance bridge

asks for trouble as well. The left hand is very sharp. As this is the mainline I expect you will be running longer engines and cars there, compared to the branch line. If you straighten out the bridge (more perpendicular to the shorter walls of the room) you will be able to install a broader curved turnout. Yes, you loose a bit of the backdrop, scenic devider space on the branchline terminus, alas you will gain lots of enjoyable smooth running on the main. Maybe rethink the layout of the terminus, as then you may more easily recurve/ smooth out the mainline. I have such a sharp curved turnout on my pike and it gives me lots of trouble. All the best, mike

Brackets

For a narrow shelf along the wall, if you aren't afraid of attaching things to the wall, there is really no need for the "L".  You can attach brackets, either metal L or shelf brackets or wooden knee braces and not have L girder.  That keeps the floor completely clear.  On the perimeter of my layout, against the wall I screwed 1x4's flat to the wall and then put brackets out from the 1x4's.  Then the road bed is supported on risers above the brackets, just as  the roadbed is support on risers above the joists on L girder.  By the time you get all the roadbed and fascia attached the L girder isn't needed for longitudinal stiffness.

If you intend to install controls or car card boxes, etc. , especially recessed controls and niches, in the fascia, the open grid is not as conducive to that, since you have a board at the front that you either have to go above or below.

On the other hand, if you want to move the layout later, the open grid has advantages.  The grids can be made a "standard" size, making them easy to unitize and pack for moving.

One other compromise between the two is to attach an L girder to the wall, and a 1x2-1x4 runner to the wall about 2 ft lower.  Then use open grid.  The back of the grids rest on the L girder and the front of the grids is supported by angle braces running from the grid down to the lower runner.  That allso keeps the floor completely clean for storage, etc,   The angle braces can attach to ends or cross braces of the grid and don't have to attach to the front of the grids.  That recesses the angle brackets and gives the appearance of the layout "floating" in the room.  Great if you want to put furniture, work benches, etc under the layout.

@Mike, those turnouts...

Mike the track "plan" is final.  I'm done futzing with it.  On the other hand, the actual track placement will be tweaked when I start laying.  That one on the closet return loop has been brought up to me before.  I don't know WHAT I was thinking when I placed it there.  You are absolutely right and it will be moved down.

I have been going back and forth about any turnout on the bridge.  But as far as the size, it is a Peco Medium radius and I won't be running anything longer than Mikados and 50' gons, it's the late 20's after all.  But it is worth reconsidering when I start laying that town out for real.  Thank you.

Size?  well, it was too small while I was designing it and I'm sure it will be too big while I'm building it!

@Dave, Your framing suggestion...

You get it, no legs unless absolutely necessary.  That turnback curve sticks out a good two feet and probably needs a couple legs.  Regarding your layout though:

I'm not following, got a picture or two, or a quick sketch?  Thanks!

Start with the walls

If you are going to anchor parts of the layout to the walls then that's where I would start. As I'm sure you know from experience, having a proper Horizontal Line is key to creating a level, even surface on which to build a layout.  Absolute precision is not necessary, but it's also not that difficult to achieve so might as well do as good of a job as possible.

I would buy or borrow a laser level.  It mounts on a tripod in the middle of a room and the laser spins in a circle.  In doing so, the laser provides a horizontal line across the entire room at the precise elevation.  I would then mount 8ft long cleats (or cut to fit) on the wall at the proper elevation.  Wall brackets can be made to hang off these cleats and then they only need one screw at the bottom of each bracket to pin it in place.  Overall you use fewer screws while ensuring the best consistency.  It's way easier than trying to precisely mount every single bracket and this method eliminates the variable of an uneven floor.

Once the cleats and brackets are in place around the whole room you can build outwards from there and put legs wherever you see fit.

Rest of the design looks pretty solid, although I'm sure you'll end up changing a few things on the track plan once you start laying down rails.

Test run it on a prototype

Richard, you are welcome. May I suggest you try out a prototype of the Peco medium turnout and the accompanying curved track pieces on a piece of plywood (or two) and run it forward and backwards thru all directions with all your engines and combinations of different length cars. That way you will get a feeling about the minimum radius that will be possible for the price of a few track nails. All the best and Merry Christmas.

Of Cleats and Protoptyes

@James, yes, I am going to try to borrow the laser level from work again.  Used it once and loved it, but just can't justify buying my own.  But I don't get

Got a picture or a quick sketch?

@Mike, I will take your advice and coble it up when I get to that point.  Thank you.

Peco Turnout radius

@Mike, I finally found the radius of the Peco curved turnouts.  If I read the the chart correctly, the inner curve is close to 17" which will be plenty for my needs.  

Brackets

Here is a picture of one of my brackets.  The is a 1x4 screwed to the studs (16" on center) as a "wall plate".  There is a horizontal joist screwed to the edge of the wall plate.  It performs the same function as a joist in open grid or a joist in L girder.   A knee brace is attached to the wall plate and the joist  to keep the joist horizontal.  I have used several lengths of knee brace, for example along one wall I alternated 12" and 16" long knee braces to facilitate putting book shelves under the layout, they fit between the 16" braces.  The roadbed (1/2 ply plus 1/2 Homasote) was supported by risers off the joints.

French Cleats

Hi Richard. I’m no woodworker, but look up “French cleats”. The board affixed to the wall has a 45 degree angle going in towards the wall. The bit being hung has a 45 degree angle which mates with this. Slide the shelf or module down and they mate securely. Lots of videos on YouTube. 

Framing, take 2

Well, here's my next take on the framing.  The arrangement outside the closet feels very Rube Goldburg-esk, but I think it will actually work.  These are the purple joists that are hung below the L girders.  Will need to add cleats to the bottom of the girders in the closet or maybe just make it into a C girder?

Thoughts?

@Ron, speaking of cleats, your suggestion of French cleats is interesting.  I've never heard of them, but on a brief review, such a technique might be perfect for mounting the couple L girders i need to mount right up against the wall.  Thank you. 

@Dave, Thanks!

@Dave, that make much more sense that what I was thinking.  (all I could imagine was a horizontal wall plate, not vertical!  Duh.)  Your suggestion is what I might end up doing in front of the closet to avoid the leg.  Again, thanks!

Couple things come to mind...

Regarding the turnout on the bridge... Have you considered moving it closer to the narrow end of the bridge?

This would give you a lot more room to get the two tracks leaving the turnout into the most ideal position to make that sharp curve at the end. Room enough to possibly get some easement built in which would help reduce potential operation issue on that curve.

Regarding the shelf brackets in the closet... It looks like the closet is 24" deep. I would consider eliminating the shelf brackets inside the closet and simply run a 2x4 cleat, bolted to the studs at the desired height, across the entire back wall of the closet. Then do the same thing across the doorways on the backside of the closet front wall. Then you could just lay "joists" across the gap from cleat to cleat anywhere you needed them along that entire length. That would be easier than getting all the shelf brackets perfectly aligned and there would be zero flex.

Additionally, you could extend 2 of the joists out through the closet door on each side of the closet center wall section to support the short bit of benchwork in the main room between the closet doors.

Agree with Dave

for the closet, except make that L-girder around the wall.  Much easier to anchor your crossers to it, and plenty of strength.

Blair

@DaveK/@Blair, great idea

Dropping the L brackets in the closet is a great idea, thank you!  I would especially make access holes in the return loop and the bottom corner MUCH easier to create.  I'm now thinking, if i were to use 3/4" plywood and 1" foam in the closet, would I even need joists?

As for the turnout on the bridge.  The inside leg has a 17" radius; quite broad by N scale standards, so I'm not worried about that.  I would really prefer moving the turnout completely off the bridge, but my CAD package said it needs to be there to keep the other radii reasonable.  Sigh.  I'll see what I can do when I actually put the track down.

Thanks again for the idea about dropping the brackets!!

1/4" ply with 1 inch foam?

  Are you planning to glue the track or roadbed on to the foam?  1/4" ply is plenty strong enough for N scale trains but it is not very rigid so joist spacing still needs to be close enough to keep it from sagging and vibrating during use. For a thin top like that I'd run continous front and rear stringers in the flat areas  along with 16 inch or so spaced joist. Nailing the plywood to the perimeter stringers and joists greatly increases it resistance to sagging( this is basically a box grid construction). For non level areas where narrow plywood roadbed is needed I'd switch to thicker plywood or laminate up spline roadbed to gain some rigidity.  

 For that lift out or lift up entry area it's pretty simple to make some plywood saddles for the ends of a lift out, or add hinges to one end for a lift up section. I have two such lift up sections on my layout and they work flawlessly.

It looks like you could eliminate the turnout on the bridge by re-arranging the turnouts in the yard and the turntale area lead.Turnouts on lift ups can work fine but they add to the complication thus affect the reliability  so best to avoid them......DaveB

@Mike, I finally found the

On modeltrainstuff.com if you look up Peco curved turnouts, it displays the specs for their "set-track" line, their Streamline line for code 100 and their code 83 north American.  It appears you are looking at the Peco Code 100 "set-track" curved turnouts (inner 17 1/4" inner & 19 7/8" outer radius).  The streamlined code 100 are 30" inner and 60" outer.  The code 83 #7 curved are 36" inner and 60" outers.

To @DaveB & @Jim

@Jim:  This is N scale, so its neither of those.  Modeltrainstuff doesn't list the medium radius curved turnout, but does list the large, calling it 36"/18" .  Which now has me worried...  On the otherhand Peco lists the inner radius for the medium radius curved turnout as 17"...   I will certainly be testing it when I get to that point.  

@DaveB:  Track will be glued to cork, then the foam.  My current layout is built this way and has joists about every 16" with no stringers and is plenty solid except where I got sloppy with the cleats and risers.  There will be fascia in front to provide some additional stability.  The bridge will be a liftout as dumb simple as i can make it.

Cost of Lumber

So I was just pricing lumber for my layout at HomeDepot.com.  1x2's for the L girders (exactly what I used on my last layout) comes to about $150.  A 4x8 sheet of 3/4" plywood ripped into 2" strips is under $70 and will give me enough material to do these same girders.

Tell me why I shouldn't trade my time ripping plywood to save over half of the cost of the 1x2s?  I can't believe that if I use #6 screws with pilot holes will likely cause significant splitting of the wood.  Any other issues or concerns?

voids

Making L girders requires screwing into the edge of the vertical piece.  That can be iffy with cheaper plywood, which can have voids (holes) in the intermediate layers.  Also cheaper plywood with only a few layers might have strength problems if you rip it as narrow as 2”.  I’d be inclined to go 3 or 4” on the vertical piece, and be careful about what plywood you get.

I'm thinking that the 3/4 inch plywood @ $70.00

Is probably furniture grade, or marine?  You want to get the plywood that has no voids between the plies.  Since you screw & glue the wood together to make the "L" girders, the screws only need to hold the wood together until the glue dries.

@Russ +1 - Use 3/4 ply as long as you screw and glue

I agree with Russ. If you screw and glue, the 3/4" ply should do fine. I used screwed and glued 3/4" ply for the L-girder supporting the upper valence of my current project and they are rock solid.

I suspect it might ultimately be better due to most 1x2s being just too soft these days. If you pay for "clear pine" they would be good enough but way more expensive.