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Finish Carpentry – Tricks and Pointers

The real test of carpentry comes when the work shifts indoors. Just about anybody can frame houses and do exterior carpentry. Sure there are expert framers, in fact, if you want to be an excellent rough carpenter you need to work as a finish carpenter for about nine to twelve months! Do this and you will see what headaches can be avoided with a few extra minutes spent getting walls square and plumb. This is especially true when it comes to hanging interior doors.

The Helix

Let's go off on a tangent quickly to prove my point. If you try to hang an interior door in a wall that is not only out of plumb but slightly twisted, the rough opening of the door is actually a helix. You can create a small example of a helix by taking a credit card and hold the four corners in your finger tips. Now slightly twist the card. That is a helix. Well, when it comes to hanging doors, you want the opening to be in the same plane. If it is not, one of two things will happen: If you want the door to fit perfectly against the door stop, then the jamb will be sticking out past the wall in one or more spots and it will be recessed somewhere else! Or, you will get the jamb to be flush everywhere but the door will not be flush with the jamb when it closes. See why rough carpenters need to take extra time to do their jobs right?


One of the materials you need when doing finish work is shims - and lots of them. They are used to level cabinets or anything else. You need them to hang doors. Shims are frequently used to install baseboard and door and window trim. Good finish carpenters always travel with two or three bundles of shims. I like to use cedar shims. They are easy to cut with a sharp razor knife and are a pleasure to work with.

Trim Profile Problems

If you are casing a door or window or even installing crown molding, don't assume that each piece of trim will have the identical profile across the face of the trim. You may get trim from different mill runs. It can get all mixed together at the lumber yard. You generally see problems when you cut the casing molding flat and try to join two 45 degree angles over a window or a door. If you have this problem you can solve it with a little sandpaper and a small sharp wood chisel.

Temperature & Humidity

Wood is a hygroscopic material. It responds to changes in humidity. This means it can expand or contract. If you are doing a large trim job, make sure the inside of the house is at or near the temperature it will be at when people live in it while you are installing the trim. What's more, make sure the trim is stored indoors for 3 or 4 days to get comfortable and acclimated with the temperature and humidity. If you take trim from a cold, damp garage and install it, it may look horrible in a week when joints start to open up. It is a common sense issue.

Finger Joints

In an effort to conserve our natural resources, some lumber mills are making wood trim from small pieces. A special machine cuts finger joints that allow small pieces to be glued together into long pieces. Finger jointed wood works fine for painted work but be careful if using it for stained work. You will see the grain changes and the finger joints through the urethane. Some finger jointed material is available with a super thin veneer over it that masks the joints. If you buy this, keep in mind that you can only sand it very lightly. Aggressive sanding may expose the core. Don't worry, you can readily get long lengths of solid trim if you desire it! It is out there!

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