Door Casing: How To Easily Install a Door Frame Casing

door casing

For those who are starting out in carpentry, door casing is the trim (generally, rectangular in shape) that surrounds the door frame. And fortunately, in most cases, installing the casing is one of the easy carpentry processes that can be achieved within a few hours, and that allows a perfect finish carpentry.

So, without further ado, let us check out the step by step procedure and some tips to go along with it, on how to install your door casing.

how to install door casing

But as usual, before starting to harp about the instructions, we should make some pertinent points about door casing. The first and very crucial factor which decides both effectiveness and preciseness of the casing is the perfect angle of the mitered corners.

Moreover, it is always easier for the DIYer to actually arrange the casing components before fixing and installing it along the wall.

The tools needed for casing generally include – Carpenters Square, corner clamps, tape measure, miter saw, drill and drill bits, and screw gun. As for the materials, the list should have – casing material (generally made from finger jointed, un-primed wood), Carpenters Glue, screws, wood filler and latex caulk.

Finally, we move onto the main procedure, which will be discussed in a step-by-step-manner.

How To Install a Door Casing

Step 1 – Sketch a plan

Most of our home oriented projects should start from paper. So, grab a sheet and pencil, and try to make a rough sketch of the casing you would want to install. The drawing paper will also come in handy for taking down the measurements, especially when it comes to those ‘short points’ of the miter (refer to the above image).

Step 2 – Measure the angles

Make use of the Carpenters Square to measure the angles of the door jamb at the upper corners on two sides (refer to the above image). If they are at perfect right angles, you will be able to cut the even 45 degree miters to fit along with the jamb’s corners. And, if the jamb corners are not at right angles, you will need to adjust the angles of the miters for the fitting purpose.

Step 3 – Measure the door

The measuring scope continues in this step. You will now need to measure the height and width of the door, so as to correctly mark the dimensions needed for the casing. When measuring height-wise, tautly place the tape from the floor level to the top jamb section.

Repeat this step for both the right and left side of the door space, so as to make sure if the collective height is uniform. If it is not so, you will need to make adjustments to your casing cuts accordingly.

After the height measurements, move on to the door jamb width measurement, and correctly note down the figures on the aforementioned paper.

Step 4 – Decide how much door jamb to reveal

Now comes the visual side to whole scenario. You will need to decide on how much door jamb to reveal. This entails exposing of the certain dimensions of the jamb edges on all sides. In conventional doors, around 1/4-inch of the jamb is revealed, while around 1/2-inch of the jamb is concealed by the casing.

So, if you want to follow this pattern, you will need to add 1/2-inch to the previous width measurement you have taken (because of two sides of the jamb), along with adding 1/4-inch to the height measurement you have taken (because of just one top side of the jamb).

Step 5 – Make the miter cuts

We come to the cutting scope (of the casing material), which should be done with a miter saw according to the calculated measurements from the earlier Step 4. Start with the miter cuts (corner angled cuts) of the top piece and then make the miter cuts of the two side pieces.

Going back to the last part of Step 2, if the corners are not at perfect right angles, you will have to make adjustments to the miters, by increasing or decreasing their angles from 45 degrees.

Tip – After the cuts are done, you should physically join these mitered corners to check if they fit correctly.

Step 6 – Make the straight cuts

Since you have achieved the precise miter cuts, it is time to move on to the straight cuts that have to be made at the bottom of the casing on both sides. Once again revert to the measurements taken in Step 4, and accordingly make these straight cuts. After this you should have three cut-out pieces of the casing, comprising of the top piece and two side pieces.

Tip – Place them against the door (preferably with the help of other people) to check if the door jamb reveal is uniform throughout the length and width, while also making sure the corners are tight.

Step 7 – Start assembling

Now comes the assembling part. You can join the corners of the cut-out pieces by laying them on the ground and gluing both the mitered corners (by applying glue on one of the corner facades). Then use a corner clamp to hold the pieces together, so as the corners are tight and the glue takes its time to set. This results in a rudimentary assembly of the casing with the top piece joined with the two side pieces.

Tip – When gluing, do take care to properly position these corners against each other.

Step 8 – Drilling the holes

Time to start with the holes! As the assembly rests on the floor (with the clamps still on), drill two holes through the top edge of the casing’s top piece into the adjoining side pieces. This means you have to repeat the same drilling process on both corners of the set-up (resulting in a total of four holes; two at each corner).

Finally, use wooden screws to hold the pieces together, and then remove the clamps. This results in a complete assembly of the casing with the top piece joined with the two side pieces by glue as well as screws.

Step 9 – Nail the door casing

Place this completed assembly of the casing over the door, and once again make sure the inner door jamb reveal is uniform (with 1/4-inch being exposed on all sides). Then you can commence with the nailing of the casing around the door.

You should start off by nailing the inner corners of the casing pieces to the concealed door jamb. Then proceed on to nail the outer parts of the casing (just within the edges) to the drywall and the framing. For the second part, you will obviously need longer nails (preferably 6d or 8d nails).

Tip – When nailing the outer parts of the casing, make sure to keep a distance of around 1/4-inch from the edges, so as to avoid splitting.

Step 10 – The finishing touches

The casing is finally installed around your door. Now, it is time to give the finishing touches to the project and make sure you like your complete door design. For starters, you should fill out those potentially nasty nail heads with wood filler. And, there can be scenarios where there are gaps between the wall and the casing due to the faulty orientation of the door jamb.

You can easily solve the predicament by applying a thin line of latex caulk (along the edges) to fill these gaps.

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