I make all my wargaming buildings from cork. I prefer it to the normal choice of foam board for several reasons; It is easier to cut, easier to glue and easier to paint. Cork is far more resilient than foamboard and considerably cheaper to buy in the UK.
The cork tiles I use are designed to be used as flooring. They are called ‘untreated cork tiles’ and are available in various thicknesses (depending on the manufacturer) varying from 3.2mm to 4mm. They are available from most DIY or home improvement stores. In the UK they cost about £5.00 for a pack of nine tiles, in the USA they seem to be about double this. A single tile is more than enough to make a 28mm scale building so each building will cost about £0.50.
Please note, you need to buy floor cork. Wall cork is not dense enough, place mats are not dense enough, cheap rolls of cork are not dense enough. Buy the right stuff to get good results.
You will only need a small set of basic tools to work with cork. Here are the primary ones:
Stanley knife or other heavy duty knife for the main cutting.
Scalpel or similar hobby knife for smaller cutting. An X-Acto is ideal.
Metal ruler for cutting.
Plastic ruler for marking up.
Pen for marking, a pencil doesn’t show up enough. I use a black ink technical pen but used to use a biro. Biro ink can bleed through paint though so be warned.
Super glue for main sticking. Use a medium to thin glue so that you have a good capillary action.
Wood glue for smaller sticking where you may need time to position things. PVA will do but a decent resin based white wood glue is better.
Cutting mat for cutting on, you’re going to be doing a lot of cutting.
You will also need some secondary tools for working on building components that aren’t cork:
Razor saw for cutting balsa wood and wood strip.
Mitre box for accurate cutting.
Sanding block for neatening cut balsa.
Masking tape for hinges and some joining.
Kitchen paper towel.
Palette for glue and some cocktail sticks or matchsticks to apply it.