Horizontally folding doors consist of a series of hinged panels. The center of each panel is suspended from an overhead track. There may be one set of panels that closes across the entire door opening, or two sets of panels may close toward the center of the door.Seal the hinged joints by installing a soft foam gasket in each joint so that it is pinched when the door is closed.Make the gaskets very soft so they do not resist closing the door. If there are two sets of doors that close from opposite sides, install a channel at the end of one panel, such that the opposing panel enters the channel when the doors close. If the channel fits fair snugly, there is no need for additional sealing at this location. If there is only one
set of panels, install the channel on the jamb.Probably the best way to seal the top of the door is to install brush seals at the top of each panel. These contact the track as the door closes. The seals tend to keep the door from closing fully, so install them so they create as little resistance as possible.To seal the bottoms of the panels, install a limp curtain-type seal on each panel that drags across the floor with minimal resistance. The door may have a bottom track to guide the bottom of the door and add strength. If the track is raised, most of the bottom seal will not contact the track until the door reaches a closed position. At that point, the bottom seal tends to keep the door from closing fully.