About this calculator
Concrete tile roof takeoff: true roof area, Marley Double Roman tiles at the right headlap for the pitch, battens, undertile membrane, and the SANS 10400-L pitch and membrane rules. Works for gable, hip and mono-pitch roofs.
How it’s calculated
True roof area = plan area including overhang × pitch factor, where pitch factor = √(1 + (rise ÷ run)²). Hip roofs with the same pitch on every side have the same area as a gable over the same footprint. Only the edges differ. Hip length = (half width) × √(2 + (rise ÷ run)²).
Marley Double Roman tiles cover 10.42 per m² at a 100 mm headlap (17.5° to 25°) and 9.66 per m² at a 75 mm headlap (26° and steeper), with 3.13 and 2.9 m of batten per m², from Marley’s technical datasheet. Other tile profiles differ, so check your tile maker’s figures.
Worked example
With these inputs:
- Roof shape
- Gable (two slopes)
- Building length (wall to wall)
- 10 m
- Building width (wall to wall)
- 8 m
- Overhang (eaves and verge)
- 300 mm
- Pitch entered as
- Degrees
- Pitch in degrees
- 26
- Roof covering
- Concrete interlocking tile (Marley Double Roman)
- In the coastal area (within 30 km of the coast)
- No
- Truss or rafter centres
- Up to 760 mm (SANS 10400-L table 4 trusses)
- Waste allowance
- 10%
the result is:
- Roof tiles needed
- 1,078 tiles
- Roof surface area
- 101.42 m²
- Plan area (with overhang)
- 91.16 m²
- Pitch factor
- × 1.113 (26°, 5.85/12)
- Eaves length
- 21.2 lin m
Tips from the trade
- Valleys, dormers and chimneys add waste. Go to 15–20% on cut-up roofs.
- SANS 10400-L asks for at least 17° with an undertile membrane and 26° without one, and a membrane on any tiled roof within 30 km of the coast.
- Order ridge material for the hips too. It is the most commonly forgotten line.
Common questions
How many roof tiles per m²?
Marley Double Roman: 10.42 per m² at a 100 mm headlap (17.5° to 25°) and 9.66 per m² at 75 mm (26° and steeper).
When is an undertile membrane compulsory?
Under SANS 10400-L (4.2.2.6), on tiled roofs pitched below 26° or at 45° and steeper, and on any tiled roof within 30 km of the coast (or below the first escarpment, if that is closer). It is recommended on all tiled roofs.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and SANS 10400 (the National Building Regulations) and your local municipality before ordering.