Hi - a problem that ive been ponering over for some time, as fat bob say, if its practical built a shelter. ive put a picture up of mine which was simple gazebo, which i then roofed with cedar shingle roof tiles which loks lovley, but blew the budget as quite expensive. ive also been invesitgating lime render which i beleive is waterproof and beatherable, essential with a clay oven. i was at first looking at putting a chimney through th eroof, but with experimentation found out that 1. I didnt need a chiunmey as the oven burns really well, and 2. the cost of a chimney and the logistics regarding flashing etc were very difficult with a wooden roof and 3. the heat dispenses really well so even with a wooden roof underside ( plywood ) theres no scorching or heating up withheat coming out of oven door. good luck if you need any more help, just contact me, ive done a lot of research into this particular issue.