Hi Mo,

Some will use a sheet of lead, some copper, some just building felt, many nothing at all. I still prefer building off of stone to OPC, and many of the "fancery" moment connections do allow for better air circulation (if moisture is a real issue in a location) A good end sealer, maybe a copper and/or felt gasket, and a simple drift pin in a stone plinth is my prefered method, often over continuous sills which I don't like closer to the ground than 600 mm if possible.

Regards,

j