How to Determine Angle Cuts for Molding

Accurately determining angles for molding is vital for achieving professional results.

Whether baseboard, casing, chair rail or crown molding, making accurate angle cuts is an important part of any molding installation. Determining exact angles can be tricky, particularly on walls and ceilings that are uneven. There are two basic types of angle cuts for molding: inside corners and outside corners.

Things You'll Need

• Miter box or miter saw
• Carpenter's square
• Bisecting adjustable square
• Block plane

Instructions

Inside Corners

1. Hold a carpenter's square up to the wall to determine if the corner is exactly 90 degrees. If the corner is more or less than 90 degrees, use a bisecting adjustable square to determine the exact angle. To do this, push the square into the corner flush with each wall and tighten the clamp on the center of the tool.

2. Set your miter box or miter saw to 45 degrees if the corner is exactly 90 degrees. If not, adjust the saw blade angle by holding one leg of the bisecting adjustable square against the fence of the miter box and aligning the saw blade with the center line on the tool.

3. Place the molding on the saw, noting the direction so that you make your cut in the right direction. Make sure that the angle created will make the front of the piece shorter than the back. Make the cut. If cutting crown molding, lay the piece on your saw as it will be positioned on the wall. The top portion should be placed against the fence of the saw and the bottom portion against the table.

Outside Corners

1. Lay your work piece on the miter box or saw and set the angle to 45 degrees. Pay close attention to the direction of the angle. You should be making your cut so that the front surface of the molding is longer than the back. When you're sure the piece is lying in the right direction, make the cuts on the two molding pieces that will meet at the outside corner

2. Hold the boards in position on the wall and check the joint.

3. Trim the two boards, if they do not fit together perfectly, using either your saw or a block plane.

Tips & Warnings

• When making outside corner cuts, make the cuts slightly longer than the exact measurement so there is room to perfect the cut with your block plane.

• Always wear eye protection when using any kind of saw.

References

• This Old House; How to Install Foam Crown Molding; Tom Silva
• This Old House; Want a Room With More Stature? Start with Baseboards; Charles Wardell