What is a buttress?
A buttress (also: contrefort) is a rectangular projection of masonry or concrete built at right angles to a wall to resist lateral forces. A buttress strengthens the wall without having to make the entire wall thicker. Buttresses are often seen on old churches, but also in modern utility and garden construction.
What is a buttress for?
Walls are not only loaded from above (weight of the roof) but also laterally:
- Earth pressure — a retaining wall holding back soil
- Wind pressure — a tall, exposed facade
- Arch thrust — arches and vaults pushing outward
- Water pressure — the wall of a pond or water basin
A buttress channels these lateral forces into the ground.
Dimensions and spacing
| Wall height | Buttress (width × depth) | Spacing |
|---|---|---|
| Up to 1.5 m | 30 × 30 cm | 3 – 4 m |
| 1.5 – 2.5 m | 40 × 40 cm | 2.5 – 3 m |
| >2.5 m | Consult engineer | Structural advice required |
Buttress in the garden
In gardens, buttresses are commonly used for:
- Retaining walls — to accommodate level differences in the ground
- High boundary walls — in masonry or precast concrete
- Ponds and water features — lateral water pressure
Materials
- Masonry (brick) — classic, visible as a decorative element
- Concrete (cast or precast) — strong, less visible
- Reinforced concrete — for high loads or poor ground conditions
Difference: buttress vs. prop
- Buttress — solid masonry or concrete, built perpendicular to the wall
- Prop — a diagonal beam or post that shores up the wall from outside (temporary or structural)
Related terms
- Retaining wall
- Reinforcement
- Pad foundation
- Concrete slab
- Masonry bond
- Prop/shore