My boot locker carpet had already been cut around the top and a drainage hole drilled into the floor by a previous owner - so i lifted out the carpet and put some polystyrene strips down leaving a channel for the drain hole, put some poly sheeting over that and up the sides to separate the top carpet - dried out the locker carpet and put it back - a bodged job that now might work - we'll see if it keeps dry, might be able to use the space now fingers crossed.