Benchwork is the underframe of a layout; it is the structure which supports your subroadbed (which, in turn, supports your trackwork). There are several types of benchwork to consider. For the simple track plans that I have included, and for most beginners, a 4' by 8' piece of plywood is the best place to start. Most benchwork starts with a frame (usually made from wood) that is one of two varieties: open grid or L-girder.
Open grid benchwork can be likened to the floors in a house. You make a box and then support the center with joists. Most beginners will want to use standard, inexpensive 2-by-4's to build a frame, 4 feet by 8 feet. You won't need more than two joists in the middle to support your plywood. Benchwork done in this manner, open grid topped with plywood, is frequently referred to as "table-top." On the other hand, if you plan on using risers, it's best to use 1-by-4 lumber for your joists, and it's also best to place them closer together.
L-girder starts out very similarly to open grid, except that there is no outer box-frame. Modelers can create very unique shapes for their layouts. Typically, the supports are made from 1-by-3 or 1-by-4's that have 1-by-2 strips attached to their edges, making upside-down L's. The L's create places for screws to attach, and these supports are attached to legs. On the L's, simple 1-by-3's are attached with screws from beneath creating the joists. Be forwarned that L-girder benchwork can be more expensive than a simple open-grid and plywood tabletop layout.
Layouts can also be suspended from ceilings or build around the walls of a room. Such layouts, around the walls, are typically built from shelves. Other layouts are created with two levels; L-girder for the lower and shelves on top. In the corners, helixes are built so that trains can travel between the levels. Modelers that belong to clubs typically build modules to standard sizes. When combined, the modules make up a complete layout.
Subroadbed and Risers
Either variety of benchwork is then topped with a sub-roadbed material. For level areas on your layout, simply attach plywood directly on top of your wooden frame. Other modelers use risers that build off of your grid to support the subroadbed, which allows a greater variety in terrain. Here, it is important to consider maximum grade- remember not to make your hills too steep.
If you're using the table top idea, purchase a sheet of 4' by 8' good-one-side plywood from your lumber yard. Thicker is usually better, but can be more expensive. At any rate, any thickness over 3/8" is usually sufficient. If you are building risers, you can use plywood as well. Cut out strips and curves from sheets of plywood and attach those to your risers. Some users find it practical to use Homasote, a pressed-fiber product, instead of or in addition to plywood, on their layouts. Homasote is preferred for its sound-deadening qualities, but it can be hard to cut, bend, and nail into.
Use 1-by-4's or 2-by-4's to build legs for your benchwork. It is important to brace the legs on two sides to ensure that they stay plumb. People tend to build their layouts tall, so that the detail is closer to the viewer's eye. Typical height is between 48 and 56 inches tall- just shy of eyelevel for most people.