How to Install a Magnetic Door or Window Security Alarm

Magnetic security alarms deter intruders by letting out a loud sound if a door or window opens when the alarm is armed. This can provide some peace of mind if you're home alone, and can be an important component of a more complete home security system. Typically these alarms include only two parts: the trigger and the alarm. Some have simple armed-unarmed settings, while others give you the option of using the sensor as a door chime as well as an alarm. They typically come with double-sided tape for quick and easy installation.

Magnetic door alarms signal unauthorized door access.

Step 1

Hold the two pieces of the security alarm to the door or window where you plan on installing it. The two pieces must be within 5 mm or 1/5-inch of each other to work properly, and must never be placed in direct sunlight. When you know where you want the pieces to be secured, make a mark on the door or window and on the framing to indicate placement. The larger piece of the alarm attaches to the door or window, while the smaller piece attaches to the door or window frame.

Step 2

Remove the casing or trim from around the door or window gently if a cutout is required to fit the two pieces of the alarm closely. Place the alarm on the trim, draw around it and cut the trim along the traced lines. For visual appeal, sand the area until the cutout looks smooth and even. Place the alarm in the cutout to verify the fit before reattaching your trim.

Step 3

Clean the area completely where the two pieces are to be installed; use alcohol to completely remove any film that may hinder the hold of the tape.

Step 4

Remove the paper backing from the larger half of the alarm and attach it to the door in the area you marked. (With some models you may have to apply the tape separately to the alarm and the door or window.) Press firmly and hold for a couple seconds.

Step 5

Attach the magnetic sensor to the frame, using the tape, following the indicators to determine the top and bottom. Models commonly have little black arrows indicating which end should be facing upward.

Step 6

Open the battery compartment and insert your batteries. There should be a switch on the bottom or side for "on" and "off." Turn the alarm on and test your security system.


  • Magnetic alarms are triggered when an armed door or window opens. It does not trigger if the door or window is broken. You should not rely completely on this type of security, as someone can break your window to crawl in without the alarm triggering.

About the Author

Eric Jonas has been writing in small-business advertising and local community newsletters since 1998. Prior to his writing career, he became a licensed level II gas technician and continues to work in the field, also authoring educational newsletters for others in the business. Jonas is currently a graduate student with a Bachelor of Arts in English and rhetoric from McMaster University.