Using benchwork as the support for your model railway layout adds permanency to your model. Traditionally, benchwork has consisted of a wooden frame topped by wood panels. This set-up creates a stable platform for mounting everything from track to scenery. Adding foam board to your benchwork as an underlay beneath the track layout, however, provides extra design options not possible with a wood-only platform. With foam, you can build downwards into your model railway set-up, adding waterways, ditches and other subterranean features.
Begin creating the tabletop frame for the bench. Cut the 5 by 10 cm (2 by 4 inch) posts into two 2.4 metre (8 feet) sections for the sides and two 1.1 metre (3 feet 8 inch) sections for the header and footer of the table.
Nail the 5 by 10 cm (2 by 4 inch) posts together so that the bed is 10 cm (4 inches) deep, with a rectangular shape measuring 2.4 by 1.2 metres (8 by 4 feet).
Cut the plywood boards to fit across the framework, creating a flat bottom on which the foam sits. Nail two 5 by 10 cm (2 by 4 inch) cross braces to the bottom of the board extending the entire length of the framework for added support.
Flip the frame over so that the 5 by 10 cm (2 by 4 inch) posts form a shallow frame with a 10 cm (4 inch) depth.
Create the legs for the benchwork by cutting 90 cm (3 feet) lengths of the 5 by 5 cm (2 by 2 inch) posts and nailing them around the sides of the framework, beginning at the corners and placing one post for every 60 cm (2 feet) of benchwork supported.
Cross brace your 5 by 5 cm (2 by 2 inch) legs by cutting and nailing sections of the smaller posts horizontally between the legs at mid-height for extra support to keep the legs from buckling.
Measure the area inside the tabletop framework. Cut the extruded foam boards to fit this area using a utility knife.
Use wood glue to build a bedding 10 cm (4 inches) high consisting of the foam boards within the framework table. Use multiple foam boards to build this bedding, enough to fill the space to the top of the frame. Spread the glue evenly along the surface of the foam board before gluing the boards; first on to the plywood forming the bottom of the frame, and then on to subsequent boards until reaching the top of the frame.
Allow the glue binding the boards to dry overnight to create a solid foam bedding 10 cm (4 inches) deep within the benchwork. This bedding can be excavated as needed by cutting with a hobby knife or a hot wire foam cutter. After cutting the foam, sand the sides of the cut foam smooth for painting, and remove all foam debris.
For heavier layouts with lots of scenery or larger scale models, nail plywood sheets to the bottom to form the floor of your benchwork.