Sound Smarter on the Jobsite: Level, Plumb, Flush, and Proud

No, this isn’t a 4-step process for installing a toilet [although those are pretty much the steps…] This is about terms that get thrown around on jobsites a lot, that you should know!

Level is perfectly horizontal, plumb is perfectly vertical, flush is stuff in line with each other, and proud is something sticking out in front of something else.

That’s it, you can stop reading here! Or, read on for more info...

Here’s a situation where we can see how some of these relationships intersect. In the upper image, A+B are in line with each other [flush], but they aren’t level - if you put a marble on top of A it would roll to B. The bottom image shows A and B being level, but not flush. A is proud of B.

Here, the same set of relationships with plumb. Since “plumb” means perfectly vertical, A+B in the top image aren’t plumb, but they are flush, since their surfaces align. The second image shows A+B as plumb, but again, A is proud of B [good job, B].

Here is an example, using kitchen cabinets. The green lines are all plumb, but the faces of the uppers and lowers (A,D and B,E) aren't flush - the upper cabinets are set further back than the lowers. The blue lines are all level, but the faces (C,F) aren't flush. If any of these relationships or alignments are off, things won't work.

“Level” is also the name of a tool, which has a little floating bubble that shows whether the surface you're testing is tilted in either direction. It can be used vertically or horizontally to check level or plumb. To get a more accurate reading, use a level that has a similar length to the thing you’re checking. A “torpedo” level is a small level [maybe 8-12” long] that’s great for when you’re laying masonry or building furniture. In framing, you’ll want a 6’ level, so the level can make contact with the majority of the length of the stud. You can make a tiny level act like a big level by tying it to a piece of string [line level]. And when reading a level, make sure to really get in there and look at the bubble straight on and at eye level.

"Plumb" can also be checked w/ a plumb bob - a pointed weight on a string. The weight used to be made out of lead. "Plumb" comes from the Latin word for lead ("plumbum", hence the origin of Pb as the chemical symbol on the Periodic Table).

To "plumb" can also mean to check the depth, as in, plumbing the depths of a lake (with a lead weight on a string, or the like) to measure how deep it is. Our word "plumbing" comes from the fact that Romans used lead pipes for water lines.

Plumb and level can also be verbs - to plumb something up means to make it perfect in the vertical direction, and to level something means the same, but in the horizontal direction. Plumbing and leveling are crucial for many things to function properly in a building. Some things you actually *don’t* want to be level or plumb - for example, plumbing waste lines need to have a slope to them, or they won’t function properly.

We can also perceive when things are even just a tiny bit out of level or plumb. Buildings settle over time, so there's usually not a truly plumb or level surface anywhere in an older building. Fixing all that gets verrrrry expensive, and isn't always necessary - it's part of the charm!

So there you have it - a quick guide on some very important construction terms that you’ll definitely hear tossed around the jobsite. Being able to understand terms like this, and use them properly, goes a long way toward clear and helpful communication among the project team!

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