How to Secure a French Door

French doors may look elegant, but looks are what they're constructed for-not security. In fact, some sets of French doors are so weak that even when they're locked, a good shove will push them open. If you like the look of French doors, though, rest assured that with the right lock system and glass you can make them almost as secure as any other door.

French Door Lock Systems
French doors are hinged at the outside of the frame and have two or more panels that swing in or out from the center of the frame. Older models, in which the active panels were locked to each other rather than to a permanent jamb, may be less secure than swinging doors.

Modern designs, though, typically use deadbolts or a multi-point (usually three-point) locking system that extend bolts from the door into the frame to secure the door to the jamb. This not only keeps intruders out, it also makes the door more weatherproof. Both doors should be fitted with mortice rack bolts (bolts fitted within the door and operated internally by a threaded key).

The first closing leaf of the French door should be secured with mortice rack bolts at the top and bottom frames. The second closing leaf should have a five-lever mortice lock together with a further two mortice bolts.

Ideally, a French door should be made of solid (not hollow) wood at least 1 3/4 inches (44 mm) thick. Locks should always be installed at a right angle to the grain of the wood in order to reduce the chances of the wood splitting if the lock is put under pressure.

For even better security, add slide-rod locks to the top and bottom of one or both of the doors. If you've got an outward opening French door, add hinge bolts, as well. These bolts should be fit 4 to 6 inches (100-150 mm) below the top hinge and above the bottom hinge.

As an alternative, you can also use surface-mounted locking pressbolts (push to lock, key to open) on each door at the top and bottom. If the style of door will support it, a mortice sash lock should be fitted on the door for extra security.

Lower plywood panels on French doors are almost always too thin, but you can easily reinforce them by screwing a sheet of 12 mm or 18 mm marine-quality plywood to the inside or outside (or both) of the panel.

Secure French Door Glass
Glass panels are, obviously, relatively easy targets for burlgars, but there are several ways you can make glass more secure. One method is to replace ordinary or "toughened" glass panels with laminated glass. Laminated glass consists of two pieces of glass bonded together with a sheet of laminate and ideally to at least 1/4 inches (6.4 mm) thick. This type of glass can stand up to an attack much better than ordinary glass.

If you'd rather not replace the glass, you can use plastic film reinforce it. Remember, too, that glass should be fit from the inside of the house so that there's no putty on the outside. If an intruder can reach the putty, he can easily scrape it away and remove the glass. To really make sure your French door is secure, adding one of the many styles of decorative grates available will do the job.

By using appropriate French door locks, plywood reinforcement, and laminated glass, you can make your French door reasonably burglar-resistant.
Even with these precautions, though, a French door is still more vulnerable than other types of doors. Depending on your risk for burglary, you may be better off replacing your French door with a single-leaf patio door.