Time to upgrade your old locks? A guide to retrofitting new mortise locks to your old door.

You’ll know when it’s finally time to retire your old trusty mortise locks. Whether it’s becoming a security issue, keys are constantly becoming lost or demagnetized, or you are looking to upgrade to a modern smart lock to automate key management. This post aims to uncover what’s involved in retrofitting a new mortise lock without having to replace the existing door.

Advice before getting started

1. Assess the integrity of the doors carefully before committing to retrofitting. Sometimes purchasing a new door can make the most financial sense and will avoid the headaches of dealing with a “Swiss cheese” door. Not to mention it may be required in some situations to conform with fire and safety standards.

2. If doors are already equipped with a mortise lock, it’s usually best to replace it with another mortise lock. It doesn’t necessarily have to be the same lock, but something with similar characteristics.

3. All mortise locks have a slightly different door preparation, so it’s important to compare the new prep against the old. Minimizing door modifications will help conserve the integrity of your door, continue to conform to fire ratings, and ultimately allow you to get more life out of your door.

4. Escutcheon locks are better than sectional locks for retrofitting. Escutcheon locks have a continuous body and will cover existing holes much better. Sectional locks are made of different components and may not hide some of the old holes.

5. In the end, sometimes things just don’t line up perfectly, and that’s okay. Don’t be afraid to use cover plates if needed. They can give your door a clean look, while adding extra reinforcement where needed.

Step 1: Locate the door templates

In order to see how the new lock will fit against the existing door preparation, it’s a good idea to start by obtaining the door templates for both the new and existing locks.

1. Find the make and model of the existing lock. If you are unsure of the make and model, send us a picture or ask a local locksmith to help confirm.

2. Once the lock model is identified, you can usually find the door template on the manufacturers website. If they do not have this, you can contact them directly and ask for this.

3. Print off (or make digital copies) of both the new and old templates. Make note of the front and back templates as they are often times different. Also take note of the scale when printing off. Always make sure to check this before comparing templates.

Step 2: Compare characteristics

Now that you have both door templates, you can now begin to compare. You can do this offsite by comparing the templates side by side, or this can be done onsite by removing a lock and overlaying the new template onto the existing door. The on-site method is always preferable, but if you’re looking for a quick comparison, the off-site method can work as well. 

1. General alignment:  Make sure that your templates are oriented and scaled correctly. Make sure you note which templates are for the front and back of the door.

2. Edge hole alignment: Also known as the “mortise pocket”. This is where the lock case slides into the edge of the door. The preparation is relatively standard in North America. The dimensions should be somewhere around 8” tall x 1.25” wide x 4.5” deep. If they are slightly off, that’s okay, this can usually be fine tuned before installing the new locks.

3. Vertical hole alignment: Commonly known as the “back set”. This is the distance from the center of the handle, to the edge of the door. This is typically between 2.5” and 2.75”. If back sets are the same, the holes for the handle, key cylinder and thumb turn will typically line up vertically. Sometimes mounting holes will be offset, so take note of these.

4. Horizontal hole alignment: This is where you will see the most variation between locks. Find the centerline of the lock case (CL Lock Case) on the templates and use that as a reference point to see how the holes line up. 

5. Body alignment: Now that you’ve compared how all the holes line up, you can now determine how well the new lock will cover the existing holes that are not being used. If the footprint of the new lock does not cover some of the holes, a cover plate may be required.

6. Strike alignment: Most of the time the door strike is offset from the center of the lock case. This is typically .375” or .5”. This can usually be found on the door template, marked as (CL Strike). Different offsets mean that you may have to adjust the position of the door strike slightly.

Make sure to compare both sides of the door, front and back.

Final thoughts

Retrofitting a new mortise lock onto an existing door can seem daunting. However, this is something that is done all the time to save money, time, as well as the environment. With that being said, careful assessment of the condition of each door is required before committing to using the existing doors. Taking the time to compare the door templates before retrofitting can optimize the integrity and aesthetics of the door by minimizing the amount of modifications and additional holes. 

If you require further advice on retrofitting or if you’d like to be put in touch with an expert to help with the comparison process, please reach out to us and we'll be happy to help!