Five Things to Know Before Installing Picture Frame Moulding

May 14, 2024
Chair Rail Moulding

Picture frame moulding is a great addition to rooms to add depth and texture to big blank walls. You can keep things simple by running a chair rail across the room and only adding boxes below, running single boxes from floor to ceiling, or adding multiple boxes vertically for extra drama.

I chose to do the latter in my master bedroom, and I love how it turned out. But here are the five things I wish I’d known before I installed my picture frame moulding. They would have saved me SO much time and frustration. I hope they make your project that much simpler!

1. Check if a chair rail will fit

With classic full-wall picture frame moulding, there is a chair rail that runs the perimeter of the room at classic height (~1/3 of wall height) with boxes of the same width above and below. The chair rail should dead end to your door and window trim for a clean, cohesive look.

However, if your door or window trim is shallower than most chair rails (mine is only 1/4” depth since much of it is hidden by a drywall layer), then a chair rail may not be the best fit for your room.

OR you’ll have to get crafty with cutting returns for your chair rail or adding on to your door and window trim to get the right depth. I decided to skip the chair rail altogether, return it for a refund, and I still loved the end result!

2. Use primed PVC base cap

PVC is a great choice for many reasons: 1) It’s flexible enough to bend to fit drywall imperfections. 2) It’s forgiving so that if you nail in a piece wrong and need to pop it out, it will leave a clean hole and not splinter like wood. 3) It’s typically less expensive than other materials. 4) It’s lightweight and easy to hold up and apply long strips by yourself for DIY.

However, when you buy, be sure to get primed PVC moulding unless you plan to prime it yourself! Unlike pine trim that only comes white when it’s pre-primed, PVC trim will be white no matter what. Save yourself the headache of chipping paint and get the pre-primed stuff.

3. Make many cuts at once

To save time and trips to the miter saw, I recommend that you make as many cuts as you can at once. Something to note is that because all of your lower boxes will likely be the same height—and same for the uppers—you can cut all of those pieces in bulk!

So if you have 10 lower boxes at 30” tall, cut 20 vertical pieces 30” tall (one piece each for the left and right box sides). Then, you can go around the room and install all of your vertical pieces at once, measure the lengths for the horizontal pieces, and make a final cut list to knock them out, too.

4. Make a spacer block

Once you choose the spacing that you will maintain throughout the room between your door/window trim and the boxes (I chose 4”), make a spacer block of that size by cutting scrap wood on a saw.

Hold your spacer block up between the door/window trim and moulding piece to get the correct spacing, and slide it up the trim as you nail it to perfectly parallel, consistently spaced lines.

5. Wait to nail vertical ends!

I cannot emphasize this enough. As you’re putting up all of your vertical pieces, leave the very ends of the pieces loose and un-nailed so that you can move it slightly side to side. When you come back to attach your horizontal piece later, there may be a slight gap between the mitered edges—even a 1/16” or 1/32” gap may be noticeable and require filler. But for such a slight difference, you can pinch the loose vertical end and the horizontal end together and nail in place to get a perfectly flush joint.

Caveat: Obviously, if you cut your horizontal piece VERY short, you don’t want to warp your vertical piece to get the edges to meet. That will just make the box look wonky.

I hope these tips help you with your own picture frame moulding project! If they work for you, please leave a comment below. I’d love to hear!

To learn more about how to cut and install trim, check out my course DIY Renovation for Beginners.

For more of my picture frame moulding journey, check out my Master Bedroom and Moulding 101 highlights on IG.

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