Need to get the glazing on my garden office but as my cladding if counter battened there's a nasty gap that I need to bridge. My initial thought was to line the openings with grey capping board as it would overlap the external cladding making a tidy weather proof edge and would leave a fully lined opening to fit the new window within. I've just however seen the picture below and though this is probably easier (and neater). Could someone identify this type of window and door frame so I can see if they're feasible. Also how weather proof is a door like this as normally the frame would include a cill with drainage holes and this looks to be without this...