How to Secure French Doors

How to Secure French Doors from Burglars

French doors are one of the weakest security points in your home due to two individual doors meeting in the middle. When they are not properly locked, or the locks provided during the installation have not been modified, these doors can be made to easily swing open even when the deadbolt and door lever have been locked.

French Door Terminology

As a locksmith company, we help people secure their french doors often, and we have found the following ways to be the most effective.

Three great ways to better secure a french door:

  1. Install a simple screw that prevents lock tampering. This is easy, affordable, and effective.
  2. Install security film to protect the glass from being broken out.
  3. For maximum door security, install new locks that join both sides of the door and secure them in place.

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Quick Answers to Common French Door Security Questions

No. French doors have a major security flaw that needs to be addressed.
No. There is an easy fix for weakest point that costs less than $1 to fix. From there, as you add security, cost can go up depending on the level of security.
Possibly. There are two ways to prevent this. You can stop the glass from being broken using security window film. Or, you can install a double deadbolt so if broken, the door still cannot be unlocked.
If you are protecting extreme valuables, doing everything we recommend will make that security one of the strongest security points in your home.

Are French Door Safe?

French doors, or double doors, are composed of two doors that meet in the middle. One door is referred to as the passive door. This is the door that is seldom used. The other door is referred to as the active door. This is the side that is normally opened and closed.

French doors suffer from the same security weaknesses as any exterior door in the home. We have written an article on How to Reinforce an Entry Door in 6 Easy Steps. Everything in that article applies here as well.

Securing Passive Door
Slide Bolt or Flush Bolt for Securing the Passive Door
But French Doors also have specific security concerns that make them more vulnerable to burglary than a standard door. Once you’ve addressed the specific double-door security weaknesses here, take a look at the above article to make sure that all your doors are reinforced.

The specific security weakness of a french door comes from the fact that the two doors meet in the middle. Because the passive side of the door is seldom used, it is secured into the top and bottom of the door frame. Most commonly this is done using flush bolts installed in the edge of the passive door (see photo).

The active door is then locked in place, by locking it into the secured passive side of the door via a deadbolt. This method of securing double doors is the most common used and relies heavily on the passive side of the door being secure at all times.

Should the passive side of the door not be secured to the door frame, the two doors can simply be pushed open without any resistance, even though the deadbolt of the active side is locked into the passive side it will just slide out as the two doors are pulled open. The photo below illustrates this point. It is viewed as if looking down on the door from the top.

The French Door Security Flaw

The Security Flaw with French Doors

A Screwdriver Can Unlock the Flush Bolt

As long as the passive door remains secure to the door’s frame, then there should be no problem.

However, the passive side of the door can easily be unlocked. There are numerous YouTube videos showing a variety of techniques to unlock a double door. All it really takes is a thin screwdriver, drywall hammer, or even a heavy coat hanger to bypass the door locks.

If you position any thin, rigid device into the seam between two doors, you can use it to latch the flush bolt, and then slide it to the unlocked position. It takes just a few seconds to open double doors using this technique.

Important: Your secured french door can be unlocked, in just a few seconds, with no visible signs of forced entry, using the above method.

How to Secure French Doors – Quick and Easy Solution

We’ll discuss a couple of ways to secure your french door, but this technique is the simplest, cheapest and easiest. It won’t address any other security weakness of the double door (such as the glass), but it will prevent someone from getting into your french doors undetected as we’ve just discussed. All it takes to prevent this bypass, is a single screw.

Using a screw to lock the flush bolt.
Insert Screw into Flush Bolt
The passive side of the door is very seldom used. Most homeowners only unlock it and use it when they are trying to get something very large into or out of the house.

Keeping that in mind, we recommend screwing screws into each flush bolt so that they cannot be slid open until the screws are removed.

This simple, cheap, DIY, double-door security improvement will prevent the above mentioned home break-in technique 100%.

To do this, slide the flush bolt into the door’s frame, securing the door. Then screw a small screw into the bottom of the flush bolt so that the bolt can not be opened until the screw is removed.

If at some point, you need this door, simply remove the screws, and then reinstall them when you no longer need to use that side of the door.

This technique, combined with the How to Reinforce an Entry Door in 6 Easy Steps, will make your double doors as secure as any door or window in the house.

But what if you want more security? You can go further by preventing the glass in the door from being shattered, buy reinforcing the door and/or by installing high security locks.




Glass Door Security Window Film

Security Window Film Prevents Window Breakage
Security Window Film, Buy on Amazon
Glass security window film has come a long way. A DIY installation of glass security film is now easily performed by most home owners and the security film will greatly enhance the security of a french door by preventing the glass from being easily broken in order to unlock the door.

Security window film is a film that is attached to the glass. This film is several millimeters thick but clear so that the beauty of the door is not diminished.

When applied to the glass, it acts to hold the glass together so that when the glass is hit, it will not break out. The glass does actually break, but the film holds it together in place.

For best installation of the security window film, remove the panel, install the film, and replace the panel into the window. When this is not possible, we use a thin bead of clear silicon around the edge of the window.

Security film is available on Amazon for great prices.

High Security French Door Locks

When I have customers with large valuables in the home, and french doors, we have often increase the security of the french door to the highest level possible. To do this, we:

  1. Install a commercial grade double sided deadbolt into the active side of the door, or alternatively
  2. Install a double side, high security deadbolt into the active side of the french door.
  3. Add one-side half deadbolts to the top and bottom of each door.

The Mul-t-Lock Ball Bearing Locks the Latch and the Strike Together.
When it comes to high security Mul-t-lock is our favorite brand. We discuss it in our online article, Best Lock Brands.

The Mul-t-lock has a feature here that is ideal for double doors. In a Mul-t-lock lock, there is a ball bearing in the bolt that will secure and lock into the strike of the other door. This makes the two doors very difficult to pull apart!

If you are investing in a Mul-t-Lock (check out the prices on Amazon) for a double french door, you do not want to get one with a thumb turn on the inside of the home. Buy a double cylinder deadbolt that takes a key on both sides. This way, if the glass is broken out, the deadbolt cannot be opened using the thumb turn.




Even if you are not spending the additional money on a Mul-t-lock, high security lock for your french door, you should upgrade the lock to a commercial grade double cylinder deadbolt for improved security. Our favorite is the Schlage 562 series. If you order on on Amazon, just take it into your local locksmith so they can key it to your existing house key before you install it. You will need existing Schlage, Emtek, or Dexter door hardware to key this lock to your exiting house key.

If you’re not sure of your options, just call your local locksmith, and they’ll be ready to help.

Really Securing that Passive French Door

Half Deadbolt Installed on French Door
Another big boost in french door security comes from eliminating the flush bolt. One of our favorite home locks is the one-sided or “half” deadbolt. This deadbolt has a thumb turn on the inside of the home, but no indication (no keyhole) on the outside of the home. That is, there is no way to tell from the outside of the home that a deadbolt is installed.

We install these at the top and bottom of both double doors. When combined with window security film and an interlocking Mul-t-lock deadbolt, your double door is virtually impenetrable. You will also not need to unscrew screws in order to have access through the passive door; you just unlock the deadbolt using the thumb turn.

Amazon sells our favorite half deadbolt (the Schlage B80 on Amazon) for less than $25 at the time of this article.

To install them though, you will need to drill holes into both your doors for the deadbolts and the door frame to prep for the latch. This is beyond the skill of most DIYers. So we recommend calling a locksmith in your local area.

French Door, Double Door Reinforcement Kit

In the beginning of this article we touched on the How to Reinforce an Entry Door in 6 Easy Steps article. Again, all the same security tips for any entry door also apply for your french door security.

There is one notable difference, that of the door reinforcement kit. That article discusses the door reinforcement kit (watch me install a door reinforcement kit on our YouTube video).

French Door Reinforcement Kit
If you want to reinforce a double entry door, you will need a special door reinforcement kit to do that. At the time of this writing, they were not available on Amazon anymore. The good news is that they are very reasonably priced on eBay, costing only a few dollars more than the standard door kit.

The kits come with everything needed to reinforce the jam, the door edge, and the hinges. They also come with 3″ screws so you don’t need to secure your french door with those tiny 1/2″ screws.

How to Secure Double Doors Summary

Securing your double french doors from the easiest bypass technique can be achieved for practically nothing by adding just one screw. But if you have high valuables and you want to secure the french door as much a possible, numerous additional things can be done to beef up the integrity of the door to its highest security level. Which you choose depends on your desired level of security and budget.





Disclosure: As an Amazon / Google Associate I may earn from qualifying purchases.


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