Wednesday, Mar. 2, 2005

Trim on stairs requires scraps, math, patience

By Tim Carter
Tribune Media Services

Q. I have wasted about 25 linear feet of solid-wood baseboard trying to get perfect cuts. The problem is not in the rooms but when I try to extend the trim moldings up the stairs of my house. No matter how I set my miter saw, the angles I cut do not work. Surely there must be an easy way to determine what the angle must be. How do you do install stair trim moldings? — B.K., Levittown, N.Y.

A. With the cost of solid-wood trim going up instead of down, you simply can’t afford to make mistakes when using expensive trim moldings. The sad fact is the answer to your dilemma was staring right at you the entire time. Scrap trim molding, a pencil and 15 seconds of time would have produced an exact template of the angles that needed to be cut.

Cutting stair trim moldings at precise angles can bring back memories of failed high school geometry tests to many a homeowner who tackles difficult carpentry tasks on an irregular basis. Perhaps the most frustrating thing is having a mental picture of how the trim should look but not being able to determine how the simple angles are created.

If you go back to your stairs and look at the flat landing and the stair stringer (the piece of wood on the side of the staircase where the treads butt into the wall), you will note that the top edge of the sloping stair stringer and the horizontal floor meet at a point. The bottom of each of the two pieces of trim will indeed meet at this precise point. But the meeting point of the top of the trim pieces is shrouded in mystery.

To determine where the tops of the two trim pieces meet up on the wall, you need to use a small piece of the wasted trim you generated. This stair trim molding can be as little as 1-foot long to serve as the tool you need.

Place the piece of trim on the flat landing and extend the bottom of the trim 3 inches over the point where the sloping stringer meets the landing. Use a sharp pencil and trace a line along the top of the entire piece of scrap trim.

Now place the trim on the sloping stringer and slide it up so the bottom of the trim projects up past the flat landing. Do so until the top of the trim intersects the pencil line you just drew on the wall. Use your pencil to trace a second line along the top of the sloped piece of trim.

Because the top and bottom of the stair trim are parallel, the first pencil line you created with the trim will be parallel with the flat landing, and the second pencil line will be parallel with the sloping stringer. Use a straightedge to connect the point where the two pencil lines meet to the point where the top of the sloped stringer meets the flat landing. This angled line represents the cut line you will create on both pieces of trim.

You do not need a fancy angle finder to determine the angle on the saw and on the piece of wood. I prefer to cut test pieces of trim and see how they fit before transferring the angles to long pieces of expensive trim. Take two pieces of the scrap trim and cut each about 1-foot long. Place one piece on the sloped stringer and slide it up the stringer until the tip of the trim just touches the intersection of the two pencil lines.

Hold the trim piece in this position and carefully make a mark on the bottom of this piece of trim where the sloped stringer meets the landing. Place the piece of trim flat on the floor and use the straightedge to create a pencil line across the face of the trim from the tip of the trim to the mark you just made on the bottom of the trim. Place the trim in your miter saw so it lies flat and rotate the blade until the blade is parallel with the pencil line. Turn on the saw and make a precise cut along this line.

Do this same exercise with the other piece of scrap trim as it sits on the landing. Once these two pieces of trim are cut and placed in position, the two angled cuts should meet perfectly and no filler should be needed at the joint. If you do this successfully, consider yourself a journeyman carpenter!