Blog, DIY Home, DIY Project


How To Add Trim Molding To Existing Window Sill

I am very excited to post this tutorial about adding trim molding to my existing window sill for 2 reasons. #1 Adding trim molding to any room, in my mind, makes the room look complete. #2 This is my first time using a nail gun. Yes, the dreaded, super terrifying nail gun. I’m not sure if it’s the loud noise it makes when the air is fill up in the compressor or nails that come flying out of it, but I believe it is the most intimidating power tool out there. Now that I have actually used it for addding trim to my windows, I am just semi-scarred of it.

Adding Trim To Existing Window Sill

Moving on. If you read my Living Room Reveal post (here) you would know I am very happy about the transformation of this room. I was thinking I was done but not quite done this room.

DIY Adding Trim Molding to Existing Window Sill

A few of the tweaks to our living room that I wanted to make, where to add trim molding around our windows and maybe doorways and also move our eye sore of a thermostat.

DIY Trim Molding to Existing Window Sill

In the photo above, you can see our windows are not completely bare. We do have the window sill and molding underneath but no trim around the windows. I thought it would be great to just add a little trim to finish things off. When researching window trim, it seems like the only thing out there now is Craftsman or Farmhouse big chunky molding around the windows. Even though I, like everyone else in the world, do love that look, I don’t think it would work well in my house. We do not have an open concept home, so for the sizes of the rooms in our house I think it would be too much. Not even sure if we will be adding molding around our doorways yet.

Window Trim To Existing Sill



  • Painters Tape
  • Nail Gun with nails
  • Miter Saw
  • My Husband (to use said miter saw)

DIY Window Molding Upgrade


So yes, the miter saw is another power tool I have yet to use. But in my defense, my husband G- is so good at using that saw…ok yeah, I’m afraid of that one too. So when it comes to cutting, it’s G- or nothing.

Window Trim Molding Upgrade

We decided to only do 3 windows this time around to “finish off” our living room, dining room, and our son A’s bedroom. We took measurements of all 3 windows and G- made our cuts. We wrote on the back of the molding which room they were for.

These moldings are already primed so I just gave them a coat of high gloss trim paint before installing them.

Adding Trim To Existing Window Sill

By the time they dried, G- had gone to work so I added the trim to the windows and held them up with painters tape. Then a decision had to be made: Would I patiently wait until the next day for G- to nail these around the window? Or would I try my luck with the with nail gun? I watched 3 YouTube videos on using a nail gun and decided to try my luck.

Easy Window Trim Molding

After enduring the noise of the compressor filling with air, the rest of the window trim install was cake. The nail gun makes a tiny hole in the molding that can easily be filled in with the caulking.

Installing Molding To Existing Window Sill

What method do I use for filling these small holes and gaps? Goop on an over excessive amount of window trim caulking and then spread it around to all the holes and gaps trying not to get any on the curtains that I should have probably removed, the floor or the family pet that is always underfoot. I went around and did this to all 3 windows we were adding window trim to.

DIY Easy Window Trim Molding Upgrade

After the caulking dries, you can not see any of the holes or gaps.

How To Add Trim To Existing Window Sill

Now all that’s left to do is add one more coat of high gloss trim paint. I didn’t even have to go along the edge of the molding that meets with the wall because I had already painted that before attaching it to the window. WIN!

How To Add Trim To Existing Window Sill

I love it! ┬áNo, it’s not major change in my living room but I do believe it makes it feel more finished. Now on to my next project.

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