We’re not experts on installing casing around windows, so we always recommend consulting with the pros for the best info. Don’t forget to check out our YouTube video tutorial of this window trim project! This post contains affiliate links which may lead to a small commission if purchased. This comes at no extra cost to you. Thanks!
Steps for Installing Casing Around Windows
We set a day aside for installing casing around windows in our new office. Here are the steps we took to make and put the new trim in place!
The Steps We Used for Installing Casing Around Windows.
- Measure the window
- Use formula to determine lengths
- Rip boards to width
- Cut boards to length
- Cut miters for biscuits
- Sand until smooth
- Align & secure to wall
- Caulk any gaps
- Prime & paint
What Tools Did We Use For Window Trim Installation?
Here is a list of the main tools we used to install basic trim around the new windows. I’ve also linked the ones we use for you, too. If you don’t have some of the bigger tools, sometimes your home improvement store will make rough cuts for you.
- Miter Saw
- Table Saw
- Plate Joiner
- Nail Gun
- Biscuits
- Nails
- Tape Measure
- Sandpaper
- Caulk
- Primer
- Paint
- Lumber (we used pine 1×4’s)
Installing Casing Around Windows in Detail
Let’s break down each step we took for installing casing around windows a bit more.
1. Measure the window
We used this tape measure to measure the space around each window that needed to be covered by trim. We decided to do a miter (angled cut) rather than a butt joint because it looks a little bit nicer, and it’s really not any extra work.
2. We used the formula below to determine cut lengths
Ian used the formula below to determine the cut lengths for each board. It determines the length of the longest side, with the cut at a 45 degree angle. The miter joint option makes it slightly different than a butt joint, but it’s nothing you can’t handle!
Horizontal Trim Length: (trim width x 2) + window width
Vertical Trim Length: (trim width x 2) + window height
We went for a nice beefy window casing, which was an upgrade from the thin stuff the old sellers had put on.
3. Rip boards to width
You can skip this step if you’re installing casing around windows at the same width as the store sells the lumber. However, we ripped the pine boards down a bit because we we working with limited space due to tricky angles in the wall. We didn’t want one side of trim to be thinner than the others, so we had to make sure they could all stay the same. We use this table saw for ripping.
4. Cut boards to length
Next, Ian used the measurements from the formula above to cut each piece of wood to length. We use this miter saw to make most of our cuts.
5. Cut miters for biscuits
After each board was cut to length, Ian used a biscuit joiner to cut the miters for the biscuits. This is the biscuit joiner we use. You can still embark on installing casing around windows without utilizing biscuits, but this step really makes installation and alignment a lot easier.
6. Sand until smooth
This is definitely a step I would be tempted to skip, but it’s important to sand each piece with sandpaper until smooth before installation. Ian took it down to 160 grit. He pointed out that this helps remove any teeth marks from the saw blade, in addition to creating a subtle, more overall finished look. If we had opted to round the edges, this is where we would have used the router table to do so.
7. Align & secure to wall
Ian used this air powered nail gun for installing casing around windows to the wall. Others have also used battery powered nail guns without issue, as well as a good ole’ fashioned hammer & nails if you must. But the power tool will really help with this step. Just make sure you’re careful not to use nails that are too big for this kind of project.
8. Caulk any gaps
This isn’t really a “fine craftsmanship” project, so the will most likely be some hairline gaps between boards. We used this caulk to fill the gaps, and then let dry for 24-48 hours.
9. Prime & paint
After the caulk was all dry, I was able to help by priming and painting the window trim. For this kind of wood, we just use 123 Primer, and we opted for Behr Ultra Pure White in matte to match the rest of the trim in the house. I semi-regret choosing matte white trim, and in the future, I’m going to go for a trim color with gloss.
Is Adding Window Trim Difficult?
Truth be told, adding trim to new windows can be basic, or incredibly extravagant. For this smaller room, we chose to go the basic route, and we’re very happy with how it turned out. While utilizing a butt joint would make the process even easier, we believe the mitered joint adds just enough of a finished look without stealing any attention from the rest of the room. Onto the next project!