This project explains how to replace the t-astragal (or simply astragal) on a pair of exterior doors. An astragal is the moulding attached to the inactive door, that contains the slide bolts, strike plate and weatherstrip to seal between the doors.
The new t-astragal is highlighted in this photo.
This is the interior view of the doors and the new t-astragal.
Split Door Astragal
The bottom end of the door astragal is bowed outward causing a gap in the weatherseal. The white section of stick-on weatherstripping (red arrow) was added by the prior homeowner in an attempt to seal the gap.
The problem with the door astragal is the wood has split around the bottom slide bolt (also called a ‘flush bolt’). The design of the slide bolt in this astragal is poor (as you will see in the following photos) it was bound to split with repeated closings of the active door bumping against the astragal, causing a “lever action” against the bolt mortise and door edge.
French Door Removal and Inspection
The hinge pins on the inactive door are removed and the door is taken to the workshop. See this article for details on how to remove a door.
The door is set on it’s side in a pair of jigs with the astragal side up. This is a view of the door bottom.
The split in the astragal around the slide bolt is clearly visible here. The slide bolt fits in a U shaped mortise. Each time the door closes, the slide bolt levers sideways in the mortise as the bolt hits the threshold, causing the astragal to split over time. The slide bolt is made of two metal halves that are held together by the mortise, so it separates as the wood splits. A very poor design that was destined to fail in my opinion.
End view of the split astragal bottom. The red lines highlight how the bottom has split and bent outward in the direction of the arrow.
The top end of the astragal and door is shown below. The fine red line (click on the image for a full size view) delineates the astragal from the door body. This door has a metal skin whose edges are folded over a wood door frame.
This project is continued in Part 2.
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