Mine is about 6 years old. My friend and I made them together and used just "plywood" it is about 1/2 inch thick but no idea what kind it is. They are 24 in. by 48 in. We put 2 layers of cotton batting because we had so much - and used cotton fabric we had to cover them. They are both still going strong - no warping. But we do live in So. Cal. and it is a very dry climate - so I can't image soaking the cover so much that it would make the board wet too. Her husband also put the small 1 x 1 boards to outline the ironing board it sits on so it doesn't move. I only use it to iron large piece of fabric.

We love our big boards - so hope you will too.