Filler Strips & Scribing

This week is all about one key element of built-ins: filler strips. A filler strip is a piece of material, in this case wood, used to fill the gap between the cabinet and the wall to achieve a built in look. You'll also see them used often in bathroom and kitchen cabinetry, and they tend to be inevitable when converting IKEA furniture to built ins, as they rarely fit perfectly. Whether you need one or not comes down to the dimensions of the room, size of the cabinets, and the slope of the wall.

This post is specifically dedicated to inset filler strips ("infills").

What is an inset filler strip? The terms inset and overlay refer to how the filler strip sits within the cabinet frame. Inset fit flush with the frame, and overlay overlap the frame, either partially or fully. Inset is generally more costly for contractors to install as they require more precision, but I've found them to be pretty straightforward as long as everything is level.

Sample photo from Houzz demonstrating the difference between inset and overlay.

Getting Started

Measure

Take three measurements between the wall and the unit: the top, the middle, and the bottom. The size of the strip you'll need to start with depends on the maximum width of the gap. For my IKEA BESTA Hack - DIY Bookshelves & Window Seat project, I was able to use a 1x3 on one side, but on the other I had about an 8" gap, so I needed a 1x10 (thanks to the uneven windows throughout my house).

Keep in mind that the nominal size of wood isn't the actual dimensions of the wood. For example, a 2x4 isn't actually 2"x4". It's1 1/2" x 3 1/2". Similarly, a 1x8 isn't actually 1" by 8". It's 3/4" x 7 1/4", which is why I had to size up to a 1x10 when faced with an 8" gap.

Scribing

Most people will find the three measurements above differ, indicating their walls are relatively uneven, curving somewhere along the way. That's where scribing comes into play. What is scribing? Scribing is the process of transferring the profile of an irregular surface onto a piece of wood so that it can be cut to fit the irregular shape. In other words, using a pencil to trace the exact curves and imperfections onto the wood so you can make those exact cuts.

There are many different tools you can use to do the actual scribing. I've linked my favorite here.

Determine the difference between the highest and the lowest points (typically the top of the wall and the bottom of the wall). That difference is how wide you'll want to set your scribing tool. Next, line up the wood along side the inside edge of the cabinet. I used painters tape to hold the wood in place while I made my scribe. Starting at the top, hold the scribe level to the floor and slowly work your way down being sure to keep the scribe level.

Cutting the Infill

Now that you've transferred the profile of the wall onto the wood, it's time to cut. You'll need a jigsaw, a handheld power saw, in order to make the necessary curved, freehand cuts.

Jig saws tend to make rough, jagged lines, so you'll want to make your cut along the back side (i.e. underneath) of the infill. The scribed lines will be visible for you to follow as you make your cut as these will be on top facing you.

If it's your first time using a jigsaw, I'd highly recommend practicing on some scrap wood first.

Once cut, dry fit the infill and make any necessary adjustments. Don't worry about minor variances, as long as it fits.

Attach the Inset

Add backing (e.g. scrap 2x4s) to give something to attach the infill to. Since this is an inset filler strip, I taped a small piece of wood the exact depth of the infill to ensure the backing was the right depth. Predrill holes and use cabinet screws to prevent damaging the cabinets. Use a nail gun to attach the infill to the 2x4 backing. Fill the nail holes with wood filler then use caulk to fill in any minor variances between the infill and the wall, as well as face trim as needed for your design.

Before caulk, paint, and trim.

The finished product

Click here for a quick recap containing additional photos and videos.