How to Replace an Exterior French Door Astragal

This project shows how to replace the exterior french door t-astragal (or simply astragal). An astragal is the moulding attached to the inactive door that contains the slide bolts, strike plate and weatherstrip to seal.

The new french door t-astragal is highlighted in this photo:

Exterior French Doors: New Aluminum Astragal

Exterior French Doors: New Aluminum Astragal


This is the interior view of the French doors and the new t-astragal:

Interior View of the New French Door Astragal

Interior View of the New French Door Astragal

This set of French Doors were in need of several repairs. So far I’ve replaced the door hinges and weatherstrip. Replacing the split and bent astragal will complete the overhaul.

Broken French Door Astragal

The bottom end of the exterior door astragal is bowed outward causing a gap in the weather stripping. The white section of stick-on weatherstripping (red arrow) was added by the prior homeowner in an attempt to seal the gap.

Exterior French Doors: Bent Astragal in Need of Repair

Exterior French Doors: Bent Astragal in Need of Repair

The problem with the original wood astragal has split around the bottom slide bolt (also called a ‘flush bolt’). The t-astragal slide bolt design is poor (as you will see in the following photos) because it was only a matter of time before the wood split due when active door closes and bumps against the astragal:

Exterior French Door Repair: Split Wood Astragal and Slide Bolt

Exterior French Door Repair: Split Wood Astragal and Slide Bolt

How to Replace an Exterior French Door Astragal

The following steps show to remove the wood astragal and install a new aluminum astragal.

The inactive French door to which the astragal is attached is removed by tapping out the hinge pins and the door is taken to the workshop. See this article for details on how to remove a door.

Astragal Repair: Remove the Inactive French Door

Astragal Repair: Remove the Inactive French Door

The exterior French door is in a pair of jigs made from scrap 2×4 blocks with the astragal side up. This is a view of the door bottom:

French Door Set in Jig for Repairs

French Door Set in Jig for Repairs

The wood astragal around the slide bolt is clearly visible in the next photo. 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. 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.

Exterior French Door Repair: Broken Astragal at the Bottom Slide Bolt

Exterior French Door Repair: Broken Astragal at the Bottom Slide Bolt

Here’s the bottom view of the split t-astragal. The red lines highlight how the wood astragal split and bent outward in the direction of the arrow.

Exterior French Doors: Wood Astragal and Weatherstrip

Exterior French Doors: Wood Astragal and Weatherstrip

The top 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.

Exterior French Door Repair: Top of Door and T-Astragal

Exterior French Door Repair: Top of Door and T-Astragal

This project is continued in How to Replace an Exterior French Door Astragal – Part 2.

Take care,

Bob Jackson

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