Old box sash windows are usually far too good a piece of craftsmanship to replace, but in winter the draught comes through every joint. At this property in Berlin-Zehlendorf we retrofitted seals to around 15 window sashes: a groove is routed into the rebate of each sash with a router, and a silicone tubular seal is pulled into it. The sash then closes onto the seal rather than onto wood. The arched window from the loft (pictured) was part of the job too – here the groove has to follow the segmental arch cleanly so the seal runs through without a kink. Result: tight windows, original fabric preserved, no more draughts.
