There are two main reasons why you may need to know how to fit a door casing. Firstly, if you have created a doorway, you must fit a door casing to create a frame to install a new door. Or, if your door lining is damaged or has been poorly fitted, then you may want to create a new lining.

Door casing can alter the appearance of your door, so choosing the right colour and style is very important to get right. Read more about different types of door casing designs here for inspiration.

Ensuring that the door lining fits perfectly is very important. If this DIY project is not completed correctly then you may have issues with your door e.g. it may not fully close or open, which can be a huge inconvenience. Below we have laid out the instructions you need to follow to tick off this huge job on your DIY to-do list.

Tools Required:

There are a few tools and materials that you will need for this project, many of which can be found in the Beesley and Fildes tool section on the website.

Screwdriver
Tape measure
Spirit level
Saw
Wood glue
Screws
Hammer
Set square

Instructions

It is important to note that door frames come in packs that contain a head and two jambs (or legs). The head is placed at the top of the door, and the legs are placed on the side of the door.

Fitting a door casing can be a difficult task, so ensure that you have dedicated yourself enough time to fit this in. Take your time, be patient and stay focused, and you should be able to get this project completed within a few hours.

Read the instructions below carefully to find out how to fit a door casing…

1. Remove the old lining

To start this project off, you will need to remove the old lining, so that you can clearly see the wall and doorway.

2. Measure and mark up the door on the lining

The first step is to measure and mark up the door on the lining. Do this by taking the jambs and aligning them with the frame of the door, and mark this length off. Now measure the head’s thickness, and subtract this from the length. Take the head and align to the top of the doorway, mark the length that is needed.

We recommend that you take measurements twice before cutting, to ensure that the lining is accurate.

3. Cut the lining

Once you are pleased with the measurements, you can cut the linings down with a saw. You will be left with the door lining that is ready to fit into place.

Browse through Beesley and Fildes's online collection of DIY materials and tools for top-quality and affordable products.

4. Assemble the lining

Now it is time to assemble the lining. Follow these instructions:

Take the head and place the legs into the two notches. You can tap the legs into place with a mallet. The legs should slide into place.
Take a screw and secure the legs into place. Take your time with this step to prevent damage.
Alter the lining so that the frame is square. Place a brace on a diagonal position across the corner, which should create a triangle.
Use your tape measure to take the measurement of the width of the top, and then mark this on a batten, which should be placed at the bottom of the door lining..
Place the batten with screws. Cut the battens so they are aligned with the edges of the lining.

5. Fit the lining into the wall

Now you can fit the lining into the wall. It should slide into place with ease.

6. Adjust if needed

If the lining does not fit into place, then you might need to adjust it. You can fix this by using wooden spaces to make adjustments,

7. Secure with screws

Once you are pleased with the lining, you can fix it into place. We recommend using 100mm screws. Insert screws into the lining, and take your time with this step, so that no damage is done to the lining or screws. If you have issues with this stage, you may need to adjust again.

Then, you can test the lining with a spirit level to ensure that it is in line. If the frame is not aligned properly, then it must be solved at this stage. Otherwise, your door might not close or open properly.

If you are interested in purchasing a new door to fit, check out Beesley and Fildes's extensive collection on our website. We have many stunning doors that will help take your home to the next level.

What size door casing do I need?

Getting the sizing right for door frames is essential. There are standard door sizes in the UK, however, there are some variations. The most common door frame size in the UK is 762 mm.

To find the size that you need, you will need to work out the opening size of the door. You can do this by measuring the door you already have in place, and add 2 inches to the width length and 2.5 inches to the height of the door.

For example, if the width of the door is 25 inches and the height is 80 inches, the opening size would be 27 inches by 82 inches.

At Beesley and Fildes, we have the following sized internal door casings:

30 x 88 mm
30 x 100 mm
30 x 143 mm
30 x 150 mm

If you are interested in finding out more about standard door sizes, read our blog post about the topic here.