I have a chimney stack which I wish to reduce in height and then to cap permanently. I do not want to reduce it below roof level if I can avoid it, for dull but sound reasons. What have people used succesfully to weatherproof the top of the reduced stack - in this case, around 34" x
18"? A paving slab with a drip groove round it might be possible, but no fun to get up there.Any other suggestions?