On July 5th, 2004, Jim McKenney brought up the problem of moisture in his raised beds in spite of their being covered and impervious to rain. Two possible solutions might be to treat the bed as a scree similar to those naturally found or constructed in which alpine plants are grown. The size of the bed's matter is great enough to allow drainage and air flow to a fair depth, and the moisture below in more dense material (earth) would both evaporate up and be carried by capillary action to a far lesser degree. In fact, watering on occasion might be required. The second technique might be to copy bonsai growers and go for a uniform mixture that is leached to remove all particulate matter smaller than is required for stability and growth. Local conditions would dictate exactly what size matter is used. In my case, I've gone so far as to use children's marbles as a base up to a small layer of sifted compost to add some organic matter on top. Watered in once, the compost drifts down far enough to give the plants something to work on until it is time to move them on (or not). For those who may not have a copy handy, I've included a site that gives the U.S.D.A.'s soil triangle of textures to standardize the U. S. description of soils. I know that other countries have different terms for some of the same mixtures, but the idea is universal. http://nesoil.com/properties/texture/sld005.htm Gary in Hilo, Hawaii, where it rains every day, and in the winter it rains all day. 200+ inches/year evenly spaced.