In house i have built in wadrobes. Want to shelve out plus put rails in. Been advised not use conti board as it is not strong enough.Shelves to have depth of 500mm, length of 1.5m approx. Local builders merchant only stock contiboard. What alternatives are there? Have seen in local 'sheds' pine shelving 18mm thick which is £30 for a 2.5m length!