How to Install Trim and Casing Moulding on a Casement Window

Hello Friday!!! It’s been a chaotic week here, how about yours?

I’m excited to be sharing more tutorials from the kitchen renovation. I hope you’ll excuse me as we jump back and forth in the renovation process. I’ve been trying to get the most relevant tutorials to you as soon as I can. Speaking of relevant, I understand there are a lot of under-dressed windows out there that need trim or could use a little more “WOW Factor”!  Is that your  case—ment? Hahahaha. Well, sit down for a minute and I’ll go over the details for installing window trim and casing on a casement window. Have no fear if you have a double hung window or other, these techniques will work for those windows too.

Replacement vs. New Construction Windows:

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But, let’s back up for a minute. I wanted to share with you a little snafu that happened with our casement window. When I ordered it, the guy taking the order asked me a few questions and somewhere there was a translation breakdown. He thought I needed a replacement window because I was replacing an existing window. What he didn’t realize is that I was increasing the size of the window opening and therefore needed a new construction window. In the end, I was stuck with the replacement window, but my handman and I used as many weather-stripping, caulking and water barrier techniques we could think of to keep it water tight.

This is what you need to know when ordering a new window: If you are removing the old and putting in a new window into the same frame, you order a replacement window. If you are expanding or changing the size of your window opening you need to order a new construction window.

Materials:

• 2×2″ boards
• 1×6″ board
• Window casing
• Back band moulding
• Small base trim
• Small crown or cove moulding
• Stool Moulding
• Jigsaw (coping saw or hand saw)
• Shims
• Utility knife
• Construction glue
• Caulk
• Caulk gun
• 3M Advanced Abrasives Sanding block
• ScotchBlue™™ Painter’s Tape 
• Finish nailer
• Finish nails
• Primer
• 3M Wood Filler 
• Putty Knife
• Paint
• 3M Tekk Protection Ear Plugs
• 3M Tekk Protection Eye Glasses

Instructions for Installing Trim, Casing and Moulding on a Window:

This is what we’re starting with. The window has been installed and I used Great Stuff foam insulation to seal any gaps around the window.

That poor window looked embarrassed to be stark naked. I knew she’d appreciate being trimmed out in the finest of moulding, so here’s how I installed trim and casing onto the casement window.

Find the center of your window (the actual window, not the frame) and leave a pencil mark. Use this mark as your guide for the stool and the window trim.

First measure and cut the window stool. You can use a jigsaw, coping saw or hand saw to cut out the edges of the stool so it fits snug against the window and has a reveal over the sides of the window. Take into consideration the width of the window casing and trim on each side and add an inch for the stool to extend beyond the trim. (see photo below to visualize the end product.)

When your stool fits, check the level of the stool and use wood shims if necessary.

Add a line of construction glue and secure the stool to the window sill with nails.

Safety note: When using a finish nailer be sure to wear eye protection and hearing protection. Don’t worry, you’ll look totally cool in your snazzy safety gear. It’s better than the missing eyeball look.

Build out your window frame by cutting a 2×2″ board for the top of the window. Level the top with shims and secure it with finish nails.

Cut two more pieces of 2×2 for the sides. Make sure you have the same reveal of the window on each side (refer back to your center mark.)

You may need to build out one side with shims to get an even reveal on both sides.  Make sure the sides are plumb. Secure the sides with finish nails and break the shims off by scoring them with a utility knife and breaking them with your hand. (You don’t have to sing the Kung Fu Fighting song when doing this, but I do.)

Time to add the side pieces of casing and backer board. The backer board  is not necessary, but I decided I really wanted to “pimp my window”.

Decide what amount reveal you want showing on the window stop. Mark this depth on the 2×2″ window stops. (I chose a 1/8″ reveal.)

Measure and cut your window casing to meet the 1/8″ reveal mark on top. Secure the window casing with finish nails.

Measure and cut the backer band to the same height. Secure with finish nails.

The window should look like this:

Cut the 1″ x 6″ board to fit even with the outer edges of the casing and backer band. Attach it above the window with more finish nails.

Cut the small cove and the small base trim pieces to fit across the top and bottom of the 1″ x 6″ board. The ends should be mitered where they meet the edges. Cut, two pieces at a 45 degree angle to act as a return for the moulding. Here’s a closer look:

Before securing the returns, add a dab of glue to hold it in place. Then use painter’s tape to hold the returns while they dry.  After the glue dries, secure the returns with a finish nail in the center of each.

The window is now “pimped out” and ready for wood filler in all of the holes.

Caulk all the seams where the trim pieces meet each other and the wall and window. Use 3M wood filler to fill all nail holes (photo below for illustrative purposes. Not my actual window.)

After the wood putty has dried, sand it smooth using a 3M Sanding abrasive sponge.

Wipe any sanding dust off. Prime and paint the window.

And you’ll never see the seams!

She’s all dressed up and ready for the dance.

I love the depth of our sill, it’s just enough to set a vase onto. I should also note that I decided to forgo the traditional apron. I ended up using pencil edge marble tiles instead.

That seemed relatively easy, don’t you think? Trimming out a window is a personal affair, so be sure to experiment and get creative with your trim moulding. Remember, it’s your house, you can dress it up the way you want!

Here are three other great window trim tutorials:

How to Install Window Trim by Remodelando la Casa

Easy Window Trim by Ana White

How to Trick Out Your Trim Molding in Five Easy Steps by Sawdust Girl

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