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DIY Window Trim Molding – Easy How To Without Miter Cuts

Learn how to add chunky window trim pieces the easy way without any complicated miter cuts or special equipment to make smaller windows look bigger.

Not all of us are blessed with old charming homes with tons of architectural character. Our builder grade house is as bare bones as it gets. But we’ve learned one of the best ways to add character to a new home is to add a window frame to basic new windows. 

In this DIY tutorial, we’ll walk you through the simple way to do your own trim project so your own windows exude the feeling of old house charm in every room.

This certainly isn’t one of those gorgeously creative DIY posts, but this little project is by far one of my favorites for adding some oomph to a space.

DIY Window Trim the easy way without any miter cuts

If you’re a home improvement beginner, you can do these easy DIY window casings with just simple straight cuts and no power tools at all. (Though power tools will speed up the process, if you’re willing to try.)

My favorite thing to DIY in our very plain new construction house is adding architectural interest, and since we’ve already done similar trim around our master bathroom‘s modern windows, I find myself drawn to the idea of chunky window molding throughout the rest of our house for a cohesive look.

You can find all kinds of versions of this similar trim all over the internet, but this is our very simple take on interior window trim without the high cost.

DIY Ideas to Add Character to Your Home

Olivia’s bedroom window before was uh… lack luster. Blah. Boooooriiiiiing.

window before without trim

I mean, what’s a bedroom with a glamorous chandelier without some pretty window trim to go with it? That’s like wearing stilettos with your jogging shorts. Joan Rivers would have never forgiven us, bless her soul.

DIY Window Trim – The Easy Way Without Miter Cuts


  • 1×2 piece of wood (length depending on your window’s overall length and width)
  • 2 1×4 boards
  • 1×6 board
  • Brad nails
  • Wood screws
  • Hammer (If you want to get the job done way faster, this cordless brad nailer rocks.)
  • Paintable caulk
  • Wood filler (for wood knots and nail holes)
  • Primer (always prime raw wood before painting)
  • Paint (I used a sample size of Valspar Du Jour and it was just enough.)
  • Jigsaw (of whatever type of saw you prefer; a hand saw can work if you don’t own power tools)
  • Nail setter
  • Fine grit sandpaper
  • Pry bar and utility knife (if you plan to remove existing trim to replace it with this method instead)

Different styles of molding can work for this method, but we used plain pine lumber to get clean lines in the finished look. You can use MDF board or other wood varieties.

For exterior application around an exterior window, you will need to use preservative-treated wood trim or composite materials to prevent moisture issues on the exterior of your home. 


Here’s the game plan. A visual is probably easier for this one.

If you are replacing existing window trim, use a utility knife first thing to score the old caulk along the inside edge and outside edge of the side casings, head casing, and window sill board. Then, remove the old trim from the wall with a pry bar. 

what lumber cuts to use around a window for Craftsman style trim

Step 1 – Make the Window Sill

1. We started on the window sill first. Cut your 1×6 to the width of the window plus 10 inches to leave an excess of 5 inches on each side.

2. Once we had the width of our 1×6 cut, we held it up against the bottom of the window to mark where to cut out the corners to fit into the window base.

how to make a window sill using a basic piece of lumber

3. Once everything looked good, we used the brad nails to attach it with a nail gun.

setting a sill for window casing using a basic piece of lumber

Step 2 – Add Window Trim Sides

4. For the sides of the trim, we held our 1x4s up on each side of the window to mark where to cut the length.

(Measuring is overrated in our house for some projects. If we can get away with lining up wood pieces, marking, and cutting, we do. It’s easier and just as accurate as going the extra step with a measuring tape.)

how to trim a window by adding 1x4 boards for basic window trim

Step 3 – Assemble the Header

5. Once the sides of the trim were up, Robert got to work on the header by cutting the remainder of the 1×6 the same length as the window sill. He cut the 1×2 in two pieces using the same length as the 1×6.

6. I didn’t get a shot of him using wood screws to secure the 1x2s to the top and bottom of the 1×6, but you can get a good idea of it from the pictures. (Sometimes I’m just in awe of his mad skills and wonder to myself how I ever got so lucky for marrying such a handy guy and forget to pick up my camera…oops.)

making a header for interior window casing without miter cuts

7. He used brad nails again to attach the header to the top of the window and made sure to secure them into studs in the wall.

making a header with 1x2 boards and 1x6 boards for easy interior window trim without miter cuts as window casing

Step 4 – Add the Apron

8. He added a length of 1×4 under the window sill too (called the apron).

9. Caulk any gaps and wood fill knots. You can get a better idea of how the 1x2s are attached to the 1×6 from this angle. See that not so pretty gap between the wood and the wall? Caulk is your best friend.

side view of DIY window trim before adding caulk - gaps happen and can be fixed

Just so you know, I posed with my caulk gun doing an oh-so-awkward Charlie’s Angels pose and somehow it mysteriously disappeared from my memory card.

Good thing my caulking is better than my modeling.

add caulk to hide gaps around interior window casing

Step 5 – Set Nails, Wood Fill, Sand, and Caulk

10. I went back over the brad nails with a nail setter one more time to make sure none were sticking out too.

set finishing nails around window casing with a nail setter

11. I gave the nail holes a fill-in with some wood filler, let dry, then sanded. 

Step 6 – Prime and Paint

12. Prime one coat on the raw wood so it will take paint more evenly and the wood knots won’t bleed through. 

13. Paint 1-2 coats in the color of your choice. We used Valspar Du Jour. 

After two coats of white paint, Olivia’s room suddenly looked so much bigger! I kid you not. And now Joan Rivers would approve of our ensemble.

finished interior window trim painted and caulked using basic lumber with no miter cuts

I have curtain panels ready to hang too, so this window is going to look so much bigger from the boring plain one before.

simple window casing using basic lumber with no miter cuts painted and caulked
finished Craftsman style easy interior window trim with no miter cuts

The Finished Window Trim

Amazing how much a little wood and paint can do, right? Also proof that caulk and wood filler can forgive a lot of sins. 

DIY window casing made with no miter cuts using basic wood boards

Once the curtains go up and the area rug I ordered arrives, this space will really be singing…er dancing. I mean this is a ballerina room after all.

What do you think? Is DIY window casing a project you could handle?

Robert is already eager to trim our living room and dining room windows, and I’m totally on board.

More DIY Window Ideas

Frequently Asked Questions

Does window trim have to match baseboards?

Not at all. Making your window and door trim, baseboards, and molding the same color can be good, but it’s not necessarily a rule.

Are window casings worth it?

Interior designers highly recommend window casings as they can make a room feel more finished, more high-end, and aesthetically pleasing.
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  1. Trim like that instantly makes a room feel more fancy. Love the look of it in Olivia’s adorable bedroom. You’re so lucky to have a husband that knows what he’s doing….and has all the right tools (that’s always my problem with projects!) Oh, and by the way, I’m a huge fan of caulking…..can I join in with you for your next Charlie’s Angels pose?!!?!

    1. Thanks, Jamie! It’s taken a lot of trial and error and a lot of hand-me-down tools for us. ๐Ÿ™‚ I’m totally down for a double trouble Charlie’s Angels pose. Haha I’ll be the awkward one.

  2. I love the simple, yet amazing transformation of the window! It totally changes the look of the room…. I am definitely pinning this for future reference. Can’t wait to see the “finished product”.

  3. You don’t happen to have an estimate on the cost do you? I only have 4 windows in my downstairs (sounds pretty sad when I say it out loud) and this would make them stand out so much more!

    1. I’ll go back and add that in, Esther. I meant to mention that. With wood, caulk, and paint sample pot, the final cost is about $25 per window, depending on the size you have. It really does help a ton. ๐Ÿ™‚ We have 6 windows downstairs that we’re wanting to do this to eventually.

      1. Hi I love this. Unfortunately I’m in a council house and they aren’t the best build where I am. One of those you can’t hang anything on the walls or can knock a nail in with your hand lol. Anyway my windows have a plastic type lip at the bottoms. How can I make the ledge? and the top piece of wood is that moulding? I also don’t have windows with space either side like yours so can I add this great look another way. I’m on my own, female and clueless with diy but really want to have a go. Thanks.

        1. Just remove the pkastic lip or ant other type of moulding that us there, you are going to cover it up anyhow, so even if it makes some large gouges it won’t matter.

        2. If you don’t have much side room door only on one side because of an adjacent wall, just omit that side or make the width less on either side