Plumbing a Wall with a Bubble Level

Jim Mallery

In the first article of this series, we examined how to frame a structure truly square using the simple Pythagoras theorum. This article will begin exploring how to get it plumb. If you are working in an crooked old house, that could be a unique concept.

Plumb Good

Plumb means straight up and down, and that is straight up and down with gravity, not with the floor, which itself might not be level. The squarest wall in the world still will have problems if it is not plumb--the greatest issue being doors that swing open or shut by themselves.

Your Eyes Can Deceive You

You can try eyeballing plumb, but it won't work. You need to be exact, not "close enough."

You also can try using Pythagoras's formula for square, and you might get the wall at 90 degrees to the floor, but that is not the best way to determine plumb. As previously mentioned, the floor itself might not be level. And besides, that method can be cumbersome in the confines of a hallway or small room.

Bubble or Bob

That leaves you with two methods, the bubble (or spirit) level, or the plumb bob. The best method is the plumb bob, but let's look at the bubble level first, in case you don't have a plumb bob.

A level can be fairly accurate, but precautions must be taken. And remember, the longer the level, the more accurate it will be. The problem for a do-it-yourselfer is that a 6-foot level is very expensive, and it has limited use around the house. You may have a 4-footer, which is okay. Smaller than that, and you are getting into "close enough."

The biggest problem with a level is that studs seldom are truly straight; they are going to have a little (or a lot) of bow in them. So if you set the level against a stud, you don't really know if the level is lined up true to the wall; it could be riding a bit of a warp.

Avoid the Warp

You can work around the warp problem by building a simple tool. Start with a 2x4 (that you know is straight), about 7 ½ feet long . Draw a string along it or set it on a surface that you know is flat to test it; you can shave the edges with a table saw to make certain it is straight. Then nail a 2-inch piece of 1x2 or ¾-inch plywood at each end.

By placing the board with the ¾-inch pieces against the wall at the top and bottom, your straight 2x4 will be true to the wall, without the disturbance of any warping in the studs. Placing your level against the straight 2x4 will give you pretty accurate reading; all you have to do is get the bubble center in the glass tube and you are relatively plumb.

But it is eyeballing that bubble that still can let some error into your plumb. That is why the plumb bob is better. We'll learn how to use it in the next article.


About the Author

Jim Mallery, a semi-retired journalist and onetime registered contractor, has extensive experience remodeling, repairing, and rebuilding homes.

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