The weight bearing floor is an old piece of MDF board. WARNING new MDF is toxic. It releases toxic fumes!. To protect the GPs form chewing on it and to keep moisture off the board (which will create fumes even in an old board) it is covered in Vinyl peal and stick tiles left over from my kitchen floor. Make certain when using a floor like this that the GPs cannot chew on any part of the wood. The wood is full of glue and is poisonous if eaten.