After a number of years of inactivity, I a planning to build a new layout (HO). since I will probably be making a number of track changes until I am satisfied, I will use a solid foundation benchwork model. In the past I have used 1/2" plywood and homosote for the top surface. But I see in the literature that the use of 3/8" MDF is often cited. Someone also suggested 1/2" soundboard (denser than homosote) as an option. I need some guidance from those who have been there before. The layout will be a 12’ by 6’ “U” pattern.
Richard;
If you are handlaying track, and driving spikes (nails) you need Homasote® or similar to hold the nails.
If you are using pre-made track, glue it to Woodland Scenics foam roadbed with Aleene’s Tacky Glue, and use the same stuff to glue the roadbed down. For the table top, use 2" min of EXTRUDED (not expanded) polystyrene, this is usually pink or blue, you can laminate thinner sheets using Liquid Nails for Projects (make sure the get the foam compatible version). Put a 3/16" sheet of luan plywood (or similar cheap material) on the bottom to mount your Tortise or SwitchMaster machines if required.
For the legs, rip 3/4" plywood into 2½" wide strips, and make L shaped pieces out them for the legs and two longnitudinal frame rails.