Planning A Model Railroad...

... is a vital task before actually building it. Mistakes made during the planning phase can result in costly consequences whereas one would rather prefer to invest this money in rolling stock or accessories.

Almost every model railroader started out with the classic "base board": a solid piece of chipboard onto which an oval with a spur and maybe a small shunting section was set up.

And this already is the first capital mistake: the chipboard base.
As the name already implies, this board is made of woodchips that are glued together under high pressure and heat. The glue, however, tends to get brittle over time and so the baseboard virtually "falls to pieces".

A far better choice is the use of coreboard or plywood. There are many quality variants out there in the market and - talking from experience - it always pays to invest money in quality benchwork in order to have a long-lived layout.

The "board" approach also has another disadvantage: Noise. Moreover, even a coreboard tends to warp over time and consequently has to be reinforced with beams underneath it. This, in turn, leads to a higher weight and also turns the whole thing into a giant resonance corpus.
Help is available in the form of "subroadbed" - relatively narrow plywood strips serving as the base for the future trackwork.

This approach of planning and building a layout automatically yields another advantage: Scenery can be built below track level without having to cut out scenery contours... a real time and dirt saver!