Level means perfectly horizontal — a surface is level when it has no slope and water does not run off it. The term is also used for the tool you use to check this: the spirit level (also called a “bubble level”). It is one of the most commonly used measuring instruments in construction.
The tool
A spirit level is a straight bar (aluminium or plastic) with one or more vials (glass tubes filled with liquid and an air bubble). When the air bubble sits exactly between the two lines, the surface is level (horizontal) or plumb (vertical).
Types
| Type | Length | Application |
|---|---|---|
| Torpedo level | 20-25 cm | Small spaces, plumbing |
| Standard spirit level | 60-80 cm | General use |
| Long spirit level | 100-200 cm | Walls, frames, floors |
| Laser level | — | Long distances, high precision |
Level vs. plumb
| Level | Plumb | |
|---|---|---|
| Direction | Horizontal (0°) | Vertical (90°) |
| Check | Horizontal vial | Vertical vial |
| Application | Floor, sill, wall plate | Stud, frame, wall |
Most spirit levels have both vials: one for horizontal, one for vertical.
When do you use a spirit level?
Almost everywhere in construction:
- Foundation and concrete slab
- Wall plate and purlins
- Installing window and door frames
- Brickwork
- Laying a deck
- Hanging furniture
- Tiling
Tips
- Calibrate — Check your spirit level: place it on a flat surface, read the bubble, rotate it 180° and read again. The bubble should be in the same position.
- Don’t drop it — A spirit level that has been dropped may be inaccurate.
- Laser level — For long distances (entire room, entire wall), a line laser is more accurate than a physical spirit level.
Related terms
- Diagonal measurement
- Plumb bob
- Slope (drainage gradient)