10 Trim Carpentry Tips

By Robert Robillard on Contractor Advice

10 Trim Carpentry Tips

I’ve partnered with Milwaukee Tool’s GRID apprentice program to share with you 10 trim carpentry tips that I’ve picked up over the years.  Alright let’s jump into the tips:

Tip 1:    Tune You Miter Saw

For accurate cuts, it’s important to calibrate your miter saw. A 1° difference over a 1-in. span will result in a 1/32-in. the gap in the finished miter joint.  (A 3° over 5-in. span gives you a 3/8-in. gap.)  You can drive a car through that!!

Safety Tip: Make sure to  have the power source (battery or cord) removed when you make those adjustments

Use a quality combination square to confirm the blade’s miter and bevel alignment, adjusting if necessary.  Check your saw manual for specific instructions on how to adjust the blade, which may involve loosening/tightening a series of set screws or bolts.

Tip 2: Mark Studs On Floor

If you have the opportunity to be on the project before the wallboard is installed take the time to mark your studs and any pipe locations on the subfloor. Those marks can be transferred onto the wall later prior if the flooring goes in before the trim.

Scarf Joint

Tip 3:   Long runs – Use A Scarf Joint

When a wall is longer than the trim boards you are installing, you’ll need to join two boards along the straight run with a splice miter.

A splice miter (also called a scarf joint) is superior to a butt joint), because it’s more visually appealing and creates more surface area for glue or adhesive to make a stronger joint.

Try to layout your Scarf joint on a stud for solid nailing. A splicing miter is typically cut at a 30° bevel. I like to make both 30° bevels without moving the setting on the saw. This is easily accomplished by cutting one trim board left-of-blade and the other right-of-blade.

Tip 4: Don’t measure – Mark Cuts With A Knife

It is more accurate to mark trim in place than to measure and then transfer numbers off your tape measure. It’s easy to misread a tape or to confuse numbers while walking to the saw. A tape can also flex and change shape, affecting accuracy. A sharp utility knife makes consistently thin, accurate marks. Pencils don’t work nearly as well because they never stay sharp.

To do this:

Place a piece of trim in position, then use the tip of the knife blade to make a knick mark on the edge of the board.

Tip 5: Use Back Bevels

Adding back bevels to trim butting against a wall corner can help with fitting. When butting trim into each other a 5-degree back cut can give you a tighter-looking fit since there is less material touching.

The beveled board is also easier to scribe or adjust with a block plane if you need to. Uneven walls or misaligned jambs make it hard to get tight-fitting miters. If your miter has a consistent gap at the front, there’s a good chance that putting a slight back bevel on the butting molding will fix the problem.

There are two fast and easy ways to cut a slight back bevel:

  1. 1st method is to cut trim vertically if it fits in your saw.
  2. 2nd method is better for larger baseboard stock. Shim the molding with a pencil and cut it flat on the saw table. You can adjust the position or thickness of the bevel by moving the pencil.

Tip 6: Cut longer and snap in place

Then fit horizontal elements, and other trim such as baseboards, clapboards, and chair rails. Mark and cut these pieces about 1/16″ inch longer than space.

Install the horizontal pieces by bowing them into position. This will give you a tight fit at each end.

Note: If you’re butting against a piece of casing, make sure it’s well-secured so it won’t move when you press against it.

Tip 7:   Use Reveals, Avoid Flush Edges

Wood moves as it dries out, as the house settles, as you cut it, and as you’re nailing it up. It’s almost impossible to get flush edges to stay that way without clamping and the time to sand properly That’s why carpenters have historically stepped casing back from the edge of door and window jambs.

Stepping trim back is what we call a reveal and it creates eye-pleasing shadow lines. It also creates different planes that make it harder for the eye to pick up discrepancies.

If a casing is installed flush to the inside of a jamb,  the eye will easily pick up even a 1/16-in. variation from top to bottom. If the casing is stepped back 1/4 in. or 3/16 in., this variation will not be nearly as evident and will be hidden in shadow much of the time.

Tip 8: Split the difference

Splitting the difference between two measurements is common in carpentry. Sometimes we have to toss out the level so our work looks like it’s mean to be there. Some examples of this are laying out roof shingles or better yet cedar clapboards.

Many adjustments are made along the courses to get the siding to courses to sit on top of doors and windows. Sometimes in order to deal with out-of-level situations, you have to forget “level,” and split-the-difference to get the layout to work.  I’ve seen this in old houses and wainscoting trim. Following the floor [or splitting the difference] is sometimes better than installing the lower baseboard dead-level: which will telegraph that the floor is out of level.

By accounting for discrepancies early and gradually, your adjustment should rarely have to be greater than 1/4 to 3/8 of an inch

Tip 9:  Parallel is more important than level or square

Some rules of carpentry change from framing to finish work. Instead of keeping track of plumb, level, and square, you now must keep finish materials parallel to the walls and floors. The eye sees diverging lines more readily than it sees plumb and level. The only exceptions are cabinets and doors, which must hang plumb to work properly.

One example of installing parallel is a kitchen island installed next to two outside walls – that are not square. Installing the island parallel to the longer wall, and the one that people see every time they walk down a hall, and into the room is a better solution than trying to square to the two walls.

Tip 10: Shaving Trim

Sometimes you need to shave-off a sliver of trim for a board to fit. To shave trim, push the casing up to the lowered, stopped miter saw blade. Raise the blade without moving the casing, and then make the cut. This removes a very small amount of materials. It works because the blade teeth are set slightly wider than the body of the blade, so the cut will take off 1/32 in.


I hope you enjoyed this 10 trim carpentry tips article, if it was the first time seeing it, toss these tips away back here in your mental toolbox. Try them out and get some reps in.

Remember to practice, discuss, and experiment with new skills and techniques to help you learn and develop.

10 Carpenter Trim Tips – video

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About the author

Robert Robillard

Carpenter / Remodeler / Editor

Rob Robillard is “The Concord Carpenter” Rob is a builder, general contractor, carpenter, woodworker, and editor of Concord Carpenter and ToolBoxBuzz As a General Contractor and carpenter, Rob owns and operates Concord Carpenter LLC. A full-service remodeling and construction company. Rob is a recognized leader in home building best practices and a source for how-to information for building professionals. On this website, Rob covers all aspects of home construction, building science, home improvement, woodworking, remodeling, and some of the best product and tool reviews. Rob is in charge of our Tool and Product Review series - Concord Carpenter Videos where we post all of our tool reviews and video tutorials. Rob approaches remodeling and building construction with a pragmatic and problem-solving approach. He enjoys using his knowledge and experience to help and educate building professionals as well as DIYers on best practices in the construction and remodeling industry. He's a strong advocate for "raising the bar" in the construction trades and promoting the trades to youth. #BeAMentor #Green2Great Craftsmanship, quality, and pride guide his journey on this channel The Concord Carpenter's motto: "Well done is better than well said!" : Read more about Rob

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