Home Improvement I Built That!

How to Easily DIY Custom Muntins for Windows

Hello Friends,

Raise your hand if you know what a muntin is. 

Now, raise your hand if you care. LOL…

I know! Right? Muntin building is one of those things that you just don’t think about until the need arises. But when the unthinkable happens and you do need a repair or replacement, it’s good to have a tutorial pinned as a quick and easy reference.

That’s where this post comes in.

Early morning peek outside a Great Room window | Muntins & Mullions | The Chelsea Project | www.thechelseaproject.com

How to Easily DIY Custom Muntins for Windows

Affiliate links are included for your convenience. A purchase generates a small commission at no cost to you.

In case you’re not familiar, muntins are the pieces of wood that come together to form window panes on a window. For some windows, the wood panes are built as a frame and individual panes are installed in the grill. For other windows, the grill is more of a faux muntin that is built as a grill and simply sticks onto a large pane of glass. The latter is the muntin type on my windows.

Window muntins are rebuilt with wood from old muntins | Muntins & Mullions | The Chelsea Project | www.thechelseaproject.com

Muntin Madness

Just to be clear, until a few months ago, I had no idea what a muntin was. I know! I was just walking around in my happy muntinless life.  #trueconfessions

But, I came to learn about muntins when we removed the grills in order to paint. Although the grills muntins are just over 20 years old, they were suffering from major dry rot. So when we popped them out of the window, they shattered into pieces. A whole lotta pieces.

Muntins can be rebuilt from old pieces of muntin wood | Muntins & Mullions | The Chelsea Project | www.thechelseaproject.com

Luckily, I was able to use some of the pieces to rebuild the muntins for four standard-sized windows. But when I got to the big window in the bay, I was out of useable wood.  And trying to buy a replacement muntin or having a single muntin grill made was a total bust. Turns out, vendors just don’t keep 20-year-old muntins in stock anymore and a custom build —-wowzers! It is blow-your-hair-back expensive.

The reason for the high cost is because the muntins have to be custom routed from a custom template so that the new muntins match the old ones. 🙁 But ya know, sometimes perfection like that is really overrated. 

And this, my friends, is one of those times.

A custom muntin made from wood matched with a stock moulding | Muntins & Mullions | The Chelsea Project | www.thechelseaproject.com

Muntin Making

Which Design Should I Use?

The sky’s the limit when it comes to designs. I chose this one because it was a little different from the rest of the windows and very easy to build. But actually, any muntin design will work as long as it fits with the home’s decor.

In fact, when I was looking for designs, I started a collection of Great Windows over on Pinterest. But truth be told, it’s really a collection of Great Muntins. Some are really easy to make and some —not so much.  Click here to follow this board.

How Much Moulding Is Needed?

To get the ball rolling, measure how many linear feet of moulding is needed based on your muntin design. For this design, I had three basic measurements:

  • Two horizontals measured left to right, just inside the window frame

  • Two long verticals, measured in between the two horizontals

  • Ten short verticals, measured from the horizontal to just inside the window frame

The total number of feet needed was just under 20, but I bought a couple of extra feet just in case.

Which Moulding Do I Use?

Take a piece of your broken muntin to the home improvement store to find the closest match. In this case, a simple screen moulding came close. The width is almost identical –well, an imperfect kind of identical.

Finding new wood to match the wood from an old muntin is challenging, but not impossible | Muntins & Mullions | The Chelsea Project | www.thechelseaproject.com

But the depth is way off and there is no beveling on the screen moulding.

The real challenge in trying to match new wood with old muntin wood is the depth and beveling | Muntins & Mullions | The Chelsea Project | www.thechelseaproject.com

Ordinarily, this means that all of the windows would have to be changed out. But in this case, the window is behind a table and will be viewed straight on. So I was able to leave the beveled muntins in the side windows of the bay and just replace the muntins in the big window.

Sometimes a new muntin can be made from a nearly identical match and sometimes not. The trick is to know the difference | Muntins & Mullions | The Chelsea Project | www.thechelseaproject.com

What Other Items Do I Need?

You’ll also need:

  • A saw

  • A level

  • Sandpaper (about 220-grit –give or take a grit)

  • Paint brush 

  • Trim Paint

  • 2-Sided Tape (located in the paint department)

How to Assemble

Because windows aren’t always plumb, suggest to measure, cut, sand, paint both sides, and install the pieces in sections.

  • The first pieces to install are the two horizontals.

  • Then, install the lower section of short verticals followed by the upper section of short verticals.

  • The last two pieces to install are the long verticals that fit between the two horizontals.

The No Miter Method

Using this little hand saw and box, which costs about $10-$15, the screen moulding is easily cut straight across the wood.

Tip: When using this tool, please read and follow all of the manufacturer’s safety instructions. For additional operator and safety information, please consult the expert at your home improvement center.

A simple miter box and hand saw will cut the wood for the custom muntins | Muntins & Mullions | The Chelsea Project | www.thechelseaproject.com

After the piece is cut, sand the end to a smooth finish. 

Install the Muntin

Once the piece is cut and sanded to a good fit, touch up the paint if needed. Let the paint dry and then attach a tiny piece of the 2-sided tape at the top and bottom of the piece. Hold a level alongside the marked space and stick the muntin to the glass. If the muntin is attached crooked, don’t fret. Just pull it off of the glass and reposition. The 2-sided tape is so easy to work with.

Continue this process until all muntins are installed.

It's easy to make custom muntins using simple butt joints | Muntins & Mullions | The Chelsea Project | www.thechelseaproject.com

This photo shows what the muntins look like from the outside.

An outside look of a custom muntin using simple butt joints | Muntins & Mullions | The Chelsea Project | www.thechelseaproject.com


And that’s all there is to it. 

Now that the muntins are finished, it’s on to the surrounding woodwork and adding light fixtures. Hope you can stay tuned for the reveal. Goodness knows, the whole family is ready for this little refresh to be done…AND done. 🙂

A peek at the unfinished kitchen nook with bay window custom muntins in place | Muntins & Mullions | The Chelsea Project | www.thechelseaproject.com

And, as always, please don’t hesitate to leave questions in the comment section. We are a community of learners and can help each other with questions and comments.

In the meantime, 

Learn to make custom muntin wood grills for windows | Muntins & Mullions | The Chelsea Project | www.thechelseaproject.com


Links (affiliate) for a miter box, level, and 2-sided tape. And since this post, I started adding volumes of woodwork to other rooms in the house. Because the wood was so much thicker, I purchased the Ryobi miter saw shown in the first box. It’s included here because I found it to be a good value for DIY woodworkers. 






  • Reply Brenda Botbyl June 20, 2017 at 7:17 pm

    Wow! Good job! Great article! Learned something new today…muntins…..now I know!

    • Reply theChelseaProject June 21, 2017 at 9:03 am

      Hi Brenda and thanks for stopping by!

  • Reply Nancy June 20, 2017 at 8:43 pm

    It looks great! The mutins are awesome and your directions are super helpful. I can’t wait to see the big reveal…it is looking so pretty!


    • Reply theChelseaProject June 21, 2017 at 9:02 am

      Hi Nancy and thanks! I’m working on the reveal, but it’s slow going. Choices…too many choices. LOL

  • Reply K.Rupp June 21, 2017 at 6:30 am

    Wow! That was educational. I had no idea they were called muntins. I have been calling them grills for years….ha! Yes I will be pinning this; the joys of home-ownership…..custom jobs for pesky problems.. ugh! Great job on that, they look great in that window! Excited to see the reveal. Thanks so much for the details and the how to’s!

    • Reply theChelseaProject June 21, 2017 at 9:01 am

      LOL.. Well I guess necessity is the mother of invention. Thanks so much for visiting and for the kind comment.

  • Reply Michelle June 21, 2017 at 7:54 am

    You always have the most informative posts and I learn so much. You are a wealth of information. They look beautiful. You did and outstanding job. I am just in awe of your home!

    • Reply theChelseaProject June 21, 2017 at 8:59 am

      Hi Michelle and thanks. What a kind comment. You are such a cherished blessing.

  • Reply Toni Harvey June 22, 2017 at 4:13 pm

    These turned out perfect Susie! And look how much money you saved by doing them yourself, so smart girl 🙂

    I learned a valuable term from my brother (he’s in the trades) that allowed me to let go of perfection. It’s called “Lifestyle” look. Unless you told someone that you made those yourself they would never know it, because our noses aren’t inches away from the things we create and build. So if it looks great standing 5 or 6 feet away then it is “perfect.” And if someone were to care that I spent $10 instead of $100+ then I don’t really want them in my home anyway 😀

    • Reply theChelseaProject June 22, 2017 at 7:26 pm

      Hi Toni and thanks! I really like the word you introduced. Lifestyle. It is so much kinder and gentler than perfection. I really appreciate your comment. Thanks so much for stopping by!

  • Reply How to Easily Distress Paint with Vaseline - The Chelsea Project July 15, 2017 at 9:24 am

    […] of Fusion’s color Ash is applied and allowed to dry between coats. If you have followed the kitchen nook and great room refresh, I used a lot of Fusion’s Coal Black and Ash on the picture frames. So, […]

  • Reply Angela Ogden December 19, 2017 at 4:25 pm

    How does the double sided tape hold up to the heat and cold? I am wanting to do these in my house, but painted black.

    • Reply theChelseaProject December 19, 2017 at 6:38 pm

      I haven’t had any problems with the tape, but my tape is inside with heat and/or AC all the time. It’s also in an area with controlled humidity…as in…not in a bathroom.

      • Reply ANGELA December 19, 2017 at 7:33 pm

        Good to know about the bathroom. I was thinking of doing them on the outside of the shower door, but maybe I shouldn’t. Thanks for responding so quickly, doesn’t happen a lot w bloggers.

  • Reply mj March 20, 2018 at 9:38 am

    Won’t the tape discolor over time (and then be visible from the outside) and then eventually fail? Even in controlled temperature/humidity, scotch tape isn’t exactly meant to last forever. Is there a more secure way to install them??

    • Reply theChelseaProject March 20, 2018 at 9:51 am

      I bought a high quality two-sided tape in the paint department at Home Depot. And I just checked the muntins…no yellowing and none of the tiny pieces have failed. I do want the option of removing the muntins if I should choose to for some reason and this tape provides this option. If…in the years to come…I need to replace the tape, it only costs a few dollars. No biggie.

  • Reply Nora Baker May 9, 2021 at 11:24 am

    Well described article! I love the this guide of DIY Custom Muntins for Windows. You are doing amazing job. Thanks.

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