How many roof tiles do I need per m² of roof? A roofing materials guide

The number of pieces per m² varies enormously with the type of tile, so applying the same reference to a curved tile and a flat interlocking one leads to a considerable calculation error. Before quoting a roof you need to separate clearly which material goes on and how much each uses.

How many pieces each type of tile takes

• Curved clay tile (Spanish/barrel): 28–32 pcs/m² (reference: 30 pcs/m²). The overlap must cover at least a third of the lower tile; in strong-wind areas or very shallow pitches, increase the overlap rather than risk it lifting in gusts.
• Clay interlocking/flat tile: 12–14 pcs/m² (reference: 13 pcs/m²). With less overlap than the curved, it demands more precise batten setting-out so the rows line up from top to bottom of the slope.
• Concrete tile: 10 pcs/m². It is somewhat heavier than the equivalent clay — check that the structure and batten are sized for that extra load, especially in refurbishments.

In all three cases an 8% margin is added over the area for breakage and extra overlaps.

Worked example

For a 40 m² roof slope with curved tile:

1. Slope area: 40 m²
2. • 8% breakage and extra overlaps: 3.2 m²
3. Total area: 43.2 m²
4. Estimated pieces (30 pcs/m²): 1,296 pcs

This is the same calculation the PresupuestoYa calculator applies automatically for the Roofer trade.

When to choose sheet or panel instead of tile

For industrial or agricultural buildings, metal roofing is the usual option:

• Corrugated sheet: +10% margin. Galvanised is cheaper but stains over time; pre-painted comes with factory colour and holds its looks better in the long run.
• Insulated sandwich panel: +8% margin. Solves roofing and thermal insulation in one piece — the polyurethane core insulates more per centimetre, the rock wool one improves fire performance.
• Corrugated fibre cement: +12% margin, the most fragile to walk on directly; always use a spreader board or walkway for maintenance.

Flat roof: waterproofing, not tiling

On flat or low-pitch roofs no tile is laid, but a waterproof membrane:

• EPDM sheet: synthetic rubber, very durable (decades), bonded or mechanically fixed, with no need for a torch.
• Bituminous felt / oxidised bitumen: the cheaper, traditional solution, installed with a torch — take extreme fire precautions during installation.

Both carry a 10% margin for overlaps.

Frequently asked questions

How many curved tiles are needed for 50 m² of roof? 50 × 1.08 = 54 m², and 54 × 30 ≈ 1,620 pieces.

Why does interlocking tile take fewer pieces per m² than curved? Because its format is larger and it has less overlap between pieces, so fewer units are needed to cover the same area.

What insulation is used under a pitched roof? Rock wool, fitted between battens. On an inverted flat roof extruded polystyrene (XPS) is used, which resists moisture and weight better when it is walkable.

Conclusion

Calculating pieces per m² according to the exact type of tile —not a generic figure— and adding the right margin for breakage is what avoids running short on site or ordering too much of a material that isn't always easy to return. Automating it gives a precise roofing quote from the first order.