Read How to Use a Plumb Line in PDF format
The plumb line is one of the simplest tools in the average homeowner’s toolbox, but it is also one of the most versatile. You should use a plumb line whenever you need to make a straight, vertical line – whether that is for hanging wallpaper, putting up a painting, or checking the angle of a door.
Making a Plumb Line
You can purchase plumb lines quite cheaply from most DIY stores. Professionally made plumb lines come in a range of sizes, and usually have heavy steel bobs. If you are doing any heavy-duty building work, it is a good idea to buy a heavy plumb line and bob, but a home-made plumb line should be good enough for most small indoor tasks.
To make a plumb line you will need:
- A long string made of nylon or twisted cotton
- A small, heavy weight which can be secured to the string
- Some brightly coloured chalk
Tie the weight to one end of the string. Crush the chalk into a cloth until the chalk has turned into fine powder, and run the string through it so that it is covered in the dust. Make sure that you are using a colour of chalk that is easy to see against the wall you are working with.
If using chalk will be too messy for the environment you are working in, hold the plumb line in place while someone else marks the vertical line with a soft pencil, using the string as a guide.
To ensure accurate measurements, use a weight of at least six to eight ounces. Choose a rope that will not stretch easily. You can improvise a plumb line with a length of string and anything that you have lying around (your watch, or keys, for example), but this is not ideal. Try to use a heavier cord (para-cord, or washing line, for example), and a weight that is sufficient to pull the string completely taught.
Working With a Plumb Line
Now you are ready to use the plumb line. Pin the loose end of the string to the top of the wall (use a nail, if possible, to ensure that the line stays secure), and let the string hang freely. The string should be long enough to cover most of the wall, but not so long that the weight touches the floor.
Lower the line gently and let the weight settle until the string stops moving. Once you are sure that the string is stationary, push the bottom of the string into the wall, just above the weight and make sure that the string is taught. With your free hand, pull the centre of the string away from the wall, and let it ping back against the wall. This should leave a line of chalk against the wall. The chalk line will be exactly vertical, and perpendicular to the ceiling. If you are hanging wallpaper, make sure that you follow this procedure to place a straight line on each wall around the room.
If you need the plumb line to stay still for a longer period of time, let the bob rest in a tub of clear, viscous oil so that it does not sway and move around every time someone walks past it.
When to Use a Plumb Line
Use a plumb line whenever you need to confirm the room’s true vertical – either when building a shed or an extension, or re-modelling an existing room. Never assume that the walls in a room are straight. If you have ever tried to replace the boring panel doors in your home with solid oak doors, you probably had to do some sanding and adjusting to make the doors fit. Even recently built homes can have crooked walls. It does not take a lot of foundation shift to make doorways and walls end up noticeably out of alignment.
When hanging wallpaper, you should always make sure that the paper is straight and that the pattern lines up neatly. Leave a little extra wallpaper at the top and the bottom, so that you can line up the repeating pattern and then trim the excess at the ceiling and the skirting board.
Establish a plumb line for each wall that you plan on papering. Allow for a half-inch overlap at the corners, for a clean and professional looking finish.
Plumb Lines vs Spirit Levels
Spirit levels are useful for small jobs such as hanging picture frames, or making sure that the shelves that you put up are straight. You can test the angle of a small object quickly and easily with a spirit level. However, for surfaces without a straight edge, or for establishing a true vertical for a large project such as making a doorway, a spirit level will not be accurate enough.
It is a good idea to carry both a plumb line and a spirit level so that you can take measurements on any scale. Some smartphones have built-in spirit levels which offer a fairly detailed level of feedback, and can be useful for simpler carpentry jobs.
The Importance of Careful Measurement
Taking the time to hang a plumb line may seem like a lot of hassle, but it is worth the effort. Once you get used to working with plumb lines, it only takes a minute or two to draw a perfect vertical line, and you can work with confidence.
If you try to guess, or assume that the ceiling is perfectly horizontal, and you can work from there, then the results could be disastrous. When you are decorating and standing close to the wall, your architrave or wallpaper may look fine. Once you have finished the job and taken a step back, however, any errors will be glaringly obvious. Do you really want to have to live with a misaligned fireplace or wonky door until you have the time and money to fix the issue? Measure carefully before you start cutting any decorating materials, and re-check your measurements and alignments regularly while you are working. If you identify a mistake early on, you are more likely to be able to fix it.