What is a mono-pitch roof?
A mono-pitch roof (also called a lean-to roof or shed roof) is a roof with a single sloping surface that runs from the high side to the low side. Unlike a gable roof (two sloping surfaces), a mono-pitch roof has no ridge. It is the simplest roof form and therefore popular for extensions, garden houses, and modern architecture.
Characteristics
| Property | Mono-pitch roof |
|---|---|
| Number of roof surfaces | 1 |
| Ridge | None |
| Construction | Simple |
| Drainage | To one side |
| Roof pitch | 5-30° (depending on roofing material) |
When do you choose a mono-pitch roof?
- Extension — Against an existing wall, the roof slopes away
- Garden house — Modern appearance, simple construction
- Shed — Especially when the shed is against a property boundary (water must not drain onto the neighbour’s land)
- Carport — One sloping surface for quick drainage
- Bike/bin shelter — Low structure with minimal roof pitch
Roof pitch
The minimum pitch depends on the roofing material:
| Roofing material | Minimum pitch |
|---|---|
| EPDM | 1.5° (1-2%) |
| Bitumen | 3° |
| Corrugated sheets (steel/plastic) | 5° |
| Roof tiles (concrete) | 25° |
| Roof tiles (ceramic) | 30° |
With a low-pitch mono-pitch roof (under 5°), it is often finished as a “flat roof” with EPDM or bitumen.
Construction
A mono-pitch roof is structurally simple:
- High wall — The rear (or upper) wall is higher than the front
- Wall plates — A wall plate on both walls
- Rafters — Run from the high wall plate to the low wall plate
- Roof sheathing or purlins — On the rafters, depending on the roofing material
No trusses are needed (those are for triangular roof forms). The rafters do all the work.
Mono-pitch roof vs. gable roof
| Mono-pitch roof | Gable roof | |
|---|---|---|
| Surfaces | 1 | 2 |
| Construction | Simpler | More complex (trusses) |
| Drainage | To one side | To two sides |
| Attic space | Less | More |
| Material costs | Lower | Higher |
| Wind | More vulnerable (large surface) | More stable |
Points of attention
- Wind load — A large, sloping surface catches a lot of wind. Secure the rafters firmly to the wall plate.
- Drainage to one side — All rain flows to the low side. Ensure a gutter that can handle this volume.
- Wall height difference — The difference in wall height determines the pitch. Calculate this in advance.
Related terms
- Gable roof
- Hipped roof
- Flat roof
- Rafter
- Wall plate
- EPDM