Super Easy Way to Case an Existing Window!

Yes – EASY!  I promise! I love the look of wood cased windows and had I known how easy and inexpensive it was to faux my own, I would have done this to every window in my last house! This is a great tutorial for anyone wanting to  fancy-up your existing windows and it doesn’t take long!

how-to-case-existing-windowsThe only lumber you need for this is a sheet of 1/2″ Purebond Plywood and 1×4 MDF boards.  I was able to case every window in my house with a few sheets of plywood and under $300!

I was lucky to enough to have our step-dad (a.k.a. our builder) teach me how to do this and I did a lot of the windows myself once he showed me how, so – It really is easy!

ripped-purebondStart by ripping down 1/2′ Purebond to the width of the sides of your window openings.  Don’t measure one window, measure them all because they are not all created equal.  If they are, you are lucky 🙂  You can see this piece is the width of the drywall around the windows – this is the piece for the top of the window.  Measure the length of the top of the window first and cut a piece of 1/2″ Purebond to fit. Using 2″ nails, nail it up so that the front edge of the plywood is flush with the edge of the window opening.

**If your boards are rough on both edges, just sand them down – if one side is smooth, use that side to face forward.***

Now measure the length of each window side and cut them down as well.

nail-plywoodI used my Rigid nailer to nail them up (aim right for the middle and nail about 5 nails along the length of the board.

step2Once all three boards are nailed up it’s time for the MDF!

Start by measuring each side of the window from the top of the window opening to the window sill.   Cut the 1×4 MDF to size.

wood-glueNext, add a thin line of wood glue to the edge of the 1/2″ plywood. You will notice the layers on the edge – do not cover the inside layer because this layer will be exposed once the window is complete.

nail-mdfNail the side pieces on first.  Make sure to expose that first layer of plywood (you can see a small edge of the plywood exposed under the MDF board.  I nailed mine up with my Ryobi Airstrike Nailer.

wrap-with-MDFNow measure the top piece from the outside edge of one side of the MDF board to the end of the other so that your top piece will be flush with both ends of the side pieces.  Add the wood glue and nail with 1 1/4″ brad nails.

mdfAnother picture of the exposed edge of the plywood.

Before you paint, fill all of your nail holes with wood filler!step-3Easy enough!!  Now time for paint 🙂


Valspar-SeineMore windows cased!

If you missed my paint color choices you can find them HERE and for all of my house build updates you can click HERE!

Thanks so much for stopping by!!!

  • Joey Kirkland

    How did you address the cut edge of the plywood (the “reveal”) when painting? Didn’t it leave a rough and unfinished edge?

    • You only expose 1/4″ and caulk it before painting. With the 1/4″ reveal it’s not noticeable, even before caulking. Hope this helps!

  • Melissa


    I have looked and looked for MDF planks and can’t find them. Did you have a sheet of MDF stripped down or were you able to find the actual planks? Thanks!

  • Donna, Mansfield, TX

    I would love to put casing around every window in my home. However, I have a couple of curved transom windows and chair rail in 3 rooms, in which, the chair rail runs from window to window, stopping at the edge of the windows. I’m not quite should how I would put the casing around either of those windows. Do you know how I would place the casing around the windows that have chair rail next to them? And, would casing look alright around a curved transom window?

  • tom

    Any reason why you cased the windows in the plywood instead of opting to just trim around the drywall? Just curious because I’m about to start a similar project and our windows are just have drywall casing.

  • Jayme Heuer

    I would LOVE to add molding to all my windows. However, living in Arizona the windows have no sills all of my windows and corners are bull nosed (rounded). Any suggestions?

    • Cinara

      I have the same sort of windows. I just used a slightly thicker plywood, and cut it to be flush with the wall instead of the beginning of the bullnose. Then when I half overlapped with the MDF you can’t tell there’s space behind for a bullnose.

      I cut my own sills using either bull nosed door jamb moulding MDF or thick pine that I routed to bullnose, depending which was cheaper for the window size. You just cut away the two back corners, so the back half sits flush in the existing window sill and the front juts out in front and the sides extend just past the side pieces of trim. Then I added the “apron” which is just a nice piece of crown moulding or trim moulding below the sill and the same width as the window. I think Ana White has a tutorial on her blog on how to mitre the ends of the apron to make it pretty.

      Not sure if my way is correct, but it works so far!

      • Jayme Heuer

        Great idea! Thanks. I will definitely try that!

  • Abby Spina

    This might be a silly question…how come you left the edge of the plywood exposed and didn’t put the mdf flush against the plywood? I want to do this, so I just want to make sure I do it right!

    • deedubbadoo

      In woodworking, it’s called a “reveal.” It just adds a bit of depth and character to the trim. It’s also done with door casings as well. Check some of the closets and bedroom doors in your home, I’ll bet you’ll find some instances of it.

  • Lynn

    Great job! I have been wanting to do this since we moved in (9 years ago). My problem is the stool component on our windows does not extend very far beyond the window opening – only about two inches. I would imagine I would have to replace the stool as well? What do you think?

    • I would do that for sure! I’m sharing a tutorial for ours very soon!

  • fethiye

    Why MDF instead of plywood? Because of cost and easy to paint with?

    • We did mdf On the front boards because you see the edges and plywood edges have to be covered.

      • fethiye

        If you are painting, the exposed edges should be covered also, no? I only had to cover the plywood edges when I stain the boards.

        I am just worried about MDF usage in a possible humid area.

        • The exposed edges of plywood are not attractive. We live in Texas with very high humidity and my sister has had MDF around her windows for 5 years with no problems. If you are concerned I would not use MDF but it would not use plywood for the front of the windows, personally.

  • Janet

    Thanks for making it look so easy!
    I’m starting to paint all my stained molding a white color, did you spray or use a brush? Think I am going to add this to a few windows as I go!

    • You could do either! We had our sprayed professionally because it is a new construction but I am going to add to them and I will just paint with a brush before I put them up! Hope this helps!

  • Rebecca Casper

    Did you do the window sills also? If so, how did you do it? I have a similar bay window in my dining area and I want to frame them, but I hate the yellow plastic sill that is already there, so I wanted to replace it. I love how the sill on your bay window wraps all the way around.

    • We did! I’ll share that tutorial very soon:)

      • Rebecca Casper


  • Andi Gummer

    We have MDF casing on all of our windows and while a less expensive option, we have found that any condensation from temp differences inside and outside have caused almost every single casing to swell and become disfigured.

    • That’s interesting… My sister has had it in her home for 5 years in Texas and no problems.

      • Andi Gummer

        It could very well be environmental. We are in MI where the temperature changes fluctuate causing increased condensation. If you are in an area that isn’t exposed to snow and ice and below zero temps, then you are probably safe. I guess I would just caution readers to research the pros and cons of MDF before installing, including its urea formaldehyde content, to see if its right for their families.