what sub roadbed to use in HO 5/8 ply - 1/2 inch homosote 2. inch foam


I am building a 2 level shelf HO layout along my basement walls. I have humidifiers, heat and A/C in the basement but humidity can vary with season

On the lower level I am modelling mountainous terrain (lumber and coal) I have a frame work with 12" placed cross members for risers and cleats. I AM USING COOKIE CUTTER method because of curves and 2-3 % grades.

My question is because of curves and grades, WHAT is the best roadbed support for cookie cutter? 3/8 Plywood, or 2 inch blue foam board, 1/2 Homosote . Can blue foam core bend for the grades and when glued to risers not sag ( what would be a safe distance between risers )

I am trying to avoid cutting plywood on the floor with the power jig saw and gazillion broken blades!

I also have 1/2 Homosote board I could use a razer-Knife or jig saw to cut

LAST, using any base and using Woodland Scenics foam sub-road bed, and DAP glue rather than spikes, HOW does one hold flex track in place and check gauge, particularly at joints on a curve, while glue dries?

That is lot to ask sorry...
Thanks to ALL!
David Miller
Are you talking about 'risers'? That which supports roadbed that is splined or of the cookie-cutter type is commonly called risers. They can be of half-inch ply of decent quality, or thicker, or I use 1X2 or scraps of 1X4 clear spruce. If your cross members and joists are vertical, you can even use your table saw or bench saw to bevel or angle the top surface to match the grade at that point.

Homasote is a compressed wood fiber product. It would not do a good job used as a structural component. Roadbed, sub-roadbed, sure, but not as a riser.
Bit of confusion here, sub-roadbed is generally whatever your base is. You've indicated you are planning to use 5/8th ply and are going to cookie cut it to form your layout's trackwork shapes. That weight of ply is excellent in regard to being more self supporting over greater spans and that will also depend on the quality of the timber used for the plies i.e. softwood V harder varieties. Also the number of plies will be a big factor in dimensional stability of the sheet, 5 plies as against 7 plies, which are the 2 most common (I have seen more in marine plies, but that would be overkill for MRR use.

You mention you have spaced your cross supports at 12". That is amply sufficient to attach risers to for your grades and raised trackwork. I would suggest using offcuts of the ply as your risers and if necessary bevel the tops to suit the angle of your grades as Crandell has said. You could also cut the riser tops to give any superelevation (banking effect) to your curves.

As far as the layers to insulate the trackwork from the sub-broadbed (noise mitigation and ease of track spiking), foam will not bend into a curve very readily, if at all (likely to snap). Have a look at Woodlands Scenic's foam risers which do both the grade and the curves in one hit, how they are made in a concertina fashion to accomplish curving for radius. The main drawback with foam to attach trackwork to is it's lack of ability to hold track spikes securely. Homasote is much better at this and it may insulate noise better as well.

I would also suggest that to get you up off the floor to cut your ply etc, invest in 2 or better 3, folding saw horses (stools) to lay your sheets on. Will save your back and knees a lot of punishment too.
sorry for the confusion I am fine with my risers 1x3 and cleats. I am deciding on the best sub-roadbed surface to attach the track to and be able to adjust it . in the past I glued 1/2 inc homosote to plywood . I is the curved loop back 22 in radius sections I have issues with "horse curves".. . With the homosote I could push in the track nails with a pliers. with plywood you need a pin vise to drill then nail . I never glued track before
Only thing I would add is where you place joints in the sections of plywood and splinting them, in particular on grades. Make sure if you have to join/splint on a grade, to put it in the middle, away from the transitions at each end so that the vertical transition curves onto and off the grade can be formed without kinks. Also try and get the end section back onto the level sections to continue over 2 risers before the next join/splint.