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DIY Door Casing Tips for Paint-grade Trim

Planning to upgrade some interior trim with your time at home? Here are some tips and tricks to achieve a pro-like finish when installing new door casing. Note that these tips for concealing errors only work for paint-grade trim. If you plan to install stain-grade trim with the wood grain still visible, then you’ll really need to dial in your carpentry skills. Good luck with that. This one’s for the painters…

You can reduce the number of brad nails (and thus nail holes to fill) by installing the trim with a combination of fasteners and construction glue.

In a perfect world, house construction would be square, plumb and level. In the real world, it’s not. When assembling door trim, concern yourself less with perfect squares and plumb lines, and instead let your guiding light be consistent reveals. The “reveal” is the exposure of one trim piece beneath another, which gives the trim its depth and shadow lines. A combination square makes a good trim gauge to measure a consistent reveal.

Shims are your friends. Uneven drywall or plaster surrounding the door can interfere with the casing laying flat. To keep the faces of mitered corners aligned flush with each other, use shims inserted behind a recessed piece to push it forward until the joint is smooth. Nail the casing securely, then cut off the shim later and hide the joint with caulk.

If you have slightly uneven outside corners where the tip of the miter is a smidgen too long, you can square up the corner with a flat file.

Whenever possible, mark your trim pieces in place rather than taking measurements and transferring those measurements to the work piece. This not only saves a step but also reduces errors that can happen when transferring the measurements.

For perfectly flush face-frames, you can sand the miter seams smooth after assembly.

Once satisfied with installation, apply a flexible and paintable caulk on all joints, then tool the joint to remove excess caulk. Fill all nail holes and miter seams with flexible, non-shrinking vinyl spackling paste, then once it’s dry, sand the repairs smooth.

Here is the caulked and spackled new door casing, ready for primer and paint, which will be the final phase that hides any errors and gives the installation a nice, slick, finished appearance.

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