First thing mate is get the loft as high of the ground as posible to let fresh air under.Mine's on paving slabs and railway sleepers.The front of the lofts are varnished with yacht varnish,the sides and back are painted with floor paint.The back corners have 6" X 6" steel plates on to stop the water getting in at the joints.The front to side joints are silliconed,same round the windows. Here's an old photo to give you some idea. Lindsay.