Roof Tiles Calculator

The number of roof tiles depends on the roof area, tile type and pitch angle. Common UK roof tiles include concrete interlocking (approximately 10 tiles per m²), clay plain tiles (approximately 60 tiles per m²) and slate (approximately 20–30 per m² depending on size). The coverage rate accounts for the overlap (gauge) between rows.

Roof area is measured on the slope, not the floor plan. For a simple pitched roof, each side is calculated as: rafter length × eaves-to-eaves width. The rafter length depends on the pitch angle and the horizontal span. At 30°, the rafter is about 15% longer than the horizontal distance; at 45°, about 41% longer.

Enter the roof dimensions, pitch angle and tile type. The calculator shows total roof area (on slope), number of tiles, ridge tiles, hip tiles (if applicable) and estimated weight per m². Roof weight matters for structural calculations — concrete tiles weigh approximately 43 kg/m², while natural slate is about 30 kg/m².

How many roof tiles do you need? Coverage depends on tile type and lap. Plain clay tiles 270×165mm: 60 tiles/m². Pantiles 280×240mm: 16-18 tiles/m². Concrete interlocking tiles (Marley Modern, Redland 49): 9-12 tiles/m². Slates 600×300mm: 18-20/m². Add 5-10% waste for cuts at edges, hips, valleys. Sample 60 m² roof × 9 tiles/m² (concrete interlocking) = 540 tiles + 10% = 594. Hips, valleys, ridges require special tiles ordered separately.

UK roof tile types and prices. Concrete interlocking (most common new builds): £0.80-£1.80/tile = £8-£18/m². Clay plain: £1.50-£4/tile = £80-£200/m² (expensive — lots needed). Clay pantile: £2-£6/tile = £40-£90/m². Natural slate (Welsh, Spanish, Brazilian): £2-£8/each = £40-£140/m². Synthetic slate (man-made composite): £2-£3/each = £25-£50/m². Conservation areas often require matching original — clay or natural slate mandatory.

Roof structure — battens, felt, breathable membrane. Beneath tiles: roofing battens 38×25mm (standard) at correct gauge (tile-specific). Below battens: roofing felt or modern breathable membrane (preferred — allows moisture to escape but stops rain). Underlay: helps if tile slips. Insulation: 270mm loft insulation OR foam/rigid board between rafters for warm roof. Ridge tiles bedded in mortar (traditional) or dry-ridge system (modern, ventilated, no maintenance). Building Regulations: all new roofs must meet U-value targets (Part L).

Re-roofing costs UK 2026. Materials only: £15-£40/m² (concrete tiles) to £80-£200/m² (clay or slate). Labour: £40-£90/m² for re-roofing. Total typical UK semi-detached 60 m² roof: £3,500-£8,000 concrete tiles; £6,000-£12,000 clay; £8,000-£15,000+ natural slate. Add scaffolding £600-£1,500. Skip hire £200-£400 for tile disposal. Removal of asbestos slates: specialist £1,500-£4,000+ extra. Most quotes include felt, battens, breathable membrane.

When to re-roof — life expectancy. Concrete tiles: 30-50 years. Clay plain tiles: 60-80 years. Clay pantiles: 60-100 years. Natural Welsh slate: 100+ years (some still original on Victorian buildings). Brazilian/Spanish slate: 30-50 years (variable quality). Synthetic slate: 30-50 years. Signs of re-roofing need: lots of broken/slipped tiles, ridge tiles loose, felt visibly damaged in loft, water staining ceiling, moss/lichen heavy growth, sagging roof line. Patch repair vs full re-roof: rule of thumb — if 15%+ of tiles broken/damaged, full re-roof more economical.