A column is a vertical load-bearing element that transfers forces from the structures above (beams, floors, roof) to the foundation. In construction, columns are the vertical counterparts of beams: beams carry loads horizontally, columns carry loads vertically.
Column vs. stud vs. post
These terms are often used interchangeably, but there are subtle differences:
| Term | Material | Context |
|---|---|---|
| Column | Concrete, steel or masonry | Structural engineering term, load-bearing structure |
| Stud | Timber | Timber frame construction, window frames |
| Post | Timber or steel | Pergolas, carports, arbours |
| Pillar | Stone or concrete | Decorative, often freestanding |
In practice: for a concrete or steel structure you say “column”, for a timber structure “post” or “stud”.
Where do columns appear?
In residential construction
- Load-bearing columns in an open floor plan where no load-bearing walls are desired
- Basement columns supporting the ground floor
- Facade columns alongside large window openings
In DIY projects
- Pergola — The posts (timber columns) carry the roof
- Carport — Freestanding columns with a roof structure on top
- Garage — For a wide garage door opening, a steel column is sometimes used instead of a wide masonry pier
- Veranda — The columns (posts) form the skeleton of the structure
Materials
Timber column
Most commonly used in garden construction and DIY:
- Common sizes: 100×100 mm, 120×120 mm, 150×150 mm
- Timber species: Douglas fir, pressure-treated spruce or hardwood
- Always place on a post anchor (never directly on concrete or in the ground)
Steel column
For heavy loads or slender structures:
- HEA or HEB profiles for heavy loads
- Box sections (square tube) for a sleek appearance
- Often used at garage doors with a large span
Concrete column
In professional construction:
- Reinforced concrete, cast in place or precast
- Square or round
- Not common in DIY projects
Calculation
The load capacity of a column depends on:
1. Material — Steel carries more than timber at the same size
2. Cross-section — The thicker, the more load capacity
3. Buckling length — The longer the column, the sooner it can buckle (bow out). A 3-metre column carries less than the same column at 2 metres.
4. Restraint — How the column is fixed top and bottom. A fixed (clamped) column is more stable than a pinned one.
> Rule of thumb for timber: A 100×100 mm Douglas fir column at a height of 2.5 metres can carry approximately 2,000-3,000 kg. For exact calculations, always consult a structural engineer.
Common mistakes
- Column too slender — A column that is too thin for its height can buckle (bow out and fail)
- Timber in the ground — Even pressure-treated timber rots when placed in the ground. Use a post anchor.
- No bracing — Columns alone cannot resist horizontal forces. Use braces, cross-bracing or a rigid connection.
Related terms
- Post
- Beam
- Girder
- Post anchor
- Fence post