Hip Roof Calculator (UK)
Free hip roof calculator for the UK. Compute surface area in m², common and hip rafter lengths, and ridge length for any equal-pitch four-sided hipped roof.
Hip Roof Calculator
How this hip roof calculator works for UK projects
Enter the building length, width, eave overhang, and pitch (in degrees by default for UK use, with X/12 available if you prefer the older convention). The calculator returns the dachfläche / roof surface area in m², the common rafter length, the hip rafter length, the ridge length, and the equivalent in roofing squares.
A hipped roof is the standard for British semi-detached and detached homes built between 1920 and 1980. It is also extremely common on modern volume-housebuilder estates because it ties cleanly into masonry gable returns and makes corner detailing easier.
The geometry, derived
The slope factor is the ratio between the actual rafter length and its horizontal run:
slope factor = 1 / cos(pitch in degrees)For a 22.5° pitch the factor is 1.082; for 30° = 1.155; for 35° = 1.221; for 45° = 1.414.
Surface area
For an equal-pitch hipped roof on a rectangular footprint, the surface area equals the gable equivalent:
roof area (m²) = (length + 2·overhang) × (width + 2·overhang) × slope factorThe two trapezoid planes plus the two triangle planes sum exactly to the rectangle of the footprint multiplied by the slope factor — a tidy result that simplifies the takeoff considerably.
Rafters
common rafter = (width/2) × slope factor
hip rafter = (width/2) × √(2 + tan²θ)Hip rafters are the longest rafters on the roof — typically 30–45% longer than commons. They run diagonally from each corner up to the ridge end and take a compound cut top and bottom. Order an extra one for cull.
Ridge
ridge length = length − widthThe overhangs cancel. On a 9 m × 7 m footprint the ridge is 2.0 m. On a square hip (W = L) it collapses to a point, giving a pyramid hip — common on Victorian detached villas and some modern porches.
UK pricing context (2026)
From recent NFRC member quotes, Checkatrade and MyBuilder data, and BBA-certified tile manufacturer pricing:
| Covering | £ / m² installed | Pitch range |
|---|---|---|
| Marley Eternit / Redland concrete interlocking | £55–£75 | 17.5°+ |
| Sandtoft / Marley plain tiles (clay or concrete) | £85–£130 | 35°+ |
| Pantiles (Sandtoft Lindum, Russell Galloway) | £75–£105 | 22.5°+ |
| Welsh natural slate | £180–£260 | 25°+ |
| Spanish or Brazilian slate (Cupa, SSQ) | £130–£180 | 25°+ |
| Standing-seam zinc (VMZINC) or aluminium | £180–£260 | 7°+ |
A 100 m² plain-tile hipped roof at £100/m² installed is roughly £10,000 for the covering alone, plus £1,800–£3,500 for scaffolding (Construction Skills CITB rates), £400–£800 for skip hire, and £600–£1,200 for the Marley RTV or Hambleside Danelaw dry-fix hip system.
Common UK-specific mistakes
Skipping the dry-fix hip system on a tear-off. BS 5534:2018 requires mechanical fixing on every hip cap regardless of bedding. NHBC inspection failure on this point is one of the most common reasons for warranty rework on volume-housebuilder estates.
Using imperial pitch on a UK tile gauge. Plain tiles are spec’d in metric gauge (typically 100 mm) and cover figures are quoted per m². Mixing 6/12 inputs with metric tile data is a recipe for under-ordering. The calculator defaults to degrees and m² for UK use.
Forgetting verge and hip clips. NHBC 7.2 requires mechanical fixing within 1 m of any hip, ridge, or verge. Order verge clips at one per tile within the 1 m zone and hip clips at one per cap — typically 8–12 per linear metre of hip.
Standards and references
- BS 5534:2018+A2:2018 — Slating and tiling for pitched roofs and vertical cladding.
- Approved Document A — Structure (rafter and hip-rafter loads).
- Approved Document C — Site preparation and resistance to contaminants and moisture.
- NHBC Standards Chapter 7.2 — Pitched roofs (warranty technical requirements).
- BBA Agrément certificates — required for tile, dry-fix, and underlay products on most warranty schemes.
- Eurocode 1 (BS EN 1991-1-3) — snow loading, applied via the UK National Annex.
Using this with the rest of the project
Once you have the m², size the framing with the roof truss calculator, price the covering with the roof cost calculator, and validate the pitch against your chosen tile’s BBA minimum with the roof pitch calculator. For a like-for-like comparison with a gable shape on the same footprint, the roof area calculator confirms that the geometric area is identical — the cost premium of a hipped roof comes from labour, hip cap material, and waste, not from the m² itself.
The hipped roof remains the British residential workhorse. Get the inputs right and every downstream estimate — covering, scaffolding, dry-fix system, NHBC sign-off — slots into a defensible range.