Metal Roof Calculator (UK)

Estimate metal roof sheet count, flashing lengths, and installed cost in GBP. Standing-seam, box-profile, corrugated, and tile-effect metal — sized to BS 5534 and Approved Document C.

Metal Roof Calculator

Estimate panel count, trim lengths, fasteners, and installed cost for a metal roof. Pricing is matched to your locale's currency and contractor rates.

Building length (m) Ridge-direction footprint Building width (m) Eave-to-eave footprint Pitch input Pitch (degrees) Panel type Gauge Region Include tear-off + disposal High-temp synthetic underlayment

Installed total

£22,395

Standing-seam, 26 ga

£148/m²

Cost per year

£448/yr

over 50-yr life

Roof surface

151.5 m²

76 panels × 5.5 m

Material takeoff

76 panels × 5.5 m
Ridge cap: 15 m
Eave trim: 30 m
Rake trim: 20.2 m
Fasteners: 1631 (7 boxes of 250)

Cost breakdown

Panels: £8,986
Trim + flashing: £854
Underlayment: £852
Fasteners: £253
Labour: £8,106
Tear-off: £1,845
Disposal: £954
Permit + overhead: £546

Estimate excludes structural reinforcement, decking replacement, snow guards, gutter work, and complex flashings (chimneys, skylights). Add 5–10% contingency for cuts, valleys, and waste on hipped roofs.

What this metal roof calculator estimates

Enter your building footprint, pitch (degrees or 1-in-X), sheet profile, and gauge — the calculator returns:

Slope-adjusted roof area in m² for both planes of a duo-pitch roof
Sheet count and length sized to your selected profile’s cover width
Trim takeoff — ridge, eaves trim, gable trim, valley flashing in linear metres
Fixings — typical 1 fixing per m² (or to manufacturer purlin-spacing density)
Underlay — Type LR breathable membrane area
Installed cost in GBP — sheets, trims, underlay, fixings, labour, strip-off, and skip hire

Costs are anchored to NFRC 2026 contractor rates (mainland UK), Checkatrade and MyBuilder 2026 medians, and manufacturer trade prices from Cladco, Tata Steel, Greencoat, Catnic, and Britmet.

Step 1 — Measure the footprint

Use the building plan footprint, not the roof area. The calculator applies the slope factor.

Length is along the ridge direction
Width is across the rake direction
Add the eaves overhang on every side (typically 200–450 mm under BS 5534 — check your detail)

Forgetting overhangs underestimates sheet count by 8–10% on a typical UK semi.

Step 2 — Pick the right sheet profile

Profile	Cost (UK, 2026)	Life	Best for
Box-profile / trapezoidal steel	£55–£75 / m² installed	40 yr	Outbuildings, agricultural, low-cost residential, garages
Tile-effect metal sheet (Britmet, Decra)	£75–£105 / m² installed	40 yr	Period properties wanting tile look with metal life
Standing-seam steel (Greencoat, Catnic Urban)	£85–£120 / m² installed	45 yr	Modern extensions, contemporary new-builds
Zinc (VMZinc, RheinZink)	£120–£180 / m² installed	70+ yr	Architectural projects, listed buildings (where permitted)
Natural copper	£200–£260 / m² installed	100+ yr	Heritage and high-end residential
Aluminium standing-seam	£130–£170 / m² installed	50+ yr	Coastal locations (no contact corrosion with salt)

Box-profile (32/1000, 34/1000) is the cheapest UK metal sheet because the sheets are wide, fixings are exposed, and installation is fast — typical labour on a single-storey gable runs £25–£35 / m². Trade-off: visible fixings need re-sealing every 15–20 years.

Standing-seam is the residential premium choice. Catnic Urban Gold and Tata Greencoat Urban are the volume products — 0.5 mm steel with a 30-year coating warranty, mechanically seamed at the field.

Tile-effect metal sheet (Britmet Profile 49, Decra Classic) gives you a tile or pantile aesthetic on a metal substrate. Popular in conservation areas where appearance matters but the homeowner wants 40-year material life.

Zinc and copper are architectural choices, typically reserved for listed buildings, contemporary architecture, or where the patina is part of the design intent. Both develop a protective oxide that self-heals over time.

Step 3 — Code, pitch, and BBA Agrément

UK metal roofing is governed by:

BS 5534:2014+A2:2018 — Slating and tiling for pitched roofs and vertical cladding (covers fixings, underlay, ventilation)
BS EN 14782 — Self-supporting metal sheet for roofing
BS EN 508-1/2/3 — Profiled steel, aluminium, and stainless metal sheet specifications
Approved Document A (structure) — wind and snow loading per BS EN 1991-1-3 and BS EN 1991-1-4
Approved Document C (resistance to moisture) — underlay and ventilation
Approved Document L (conservation of fuel) — insulation continuity

Always specify a sheet system with current BBA Agrément certificate (Tata Greencoat: BBA 14/5142; Catnic Urban: BBA 16/5345; Britmet: BBA 04/4112). Lender’s surveyors and building control will check.

Minimum pitches under typical manufacturer warranties:

Standing-seam steel: 3° (1 in 20) with continuous seam, 6° (~10°) without
Box-profile / trapezoidal: 5° (1 in 12) with end-lap sealant tape and stitching
Tile-effect metal: 12° minimum
Pantile-effect metal: 14° minimum

Step 4 — Strip-off, underlay, and battens

Strip-off (UK term for tear-off): if you’re re-roofing over an existing slate or tile roof, the old covering and battens come off. Existing breathable membrane is normally re-used only if it’s <5 years old, undamaged, and Type LR rated. Otherwise, strip back to rafters and re-felt.

Underlay: BS 5534 mandates Type LR breathable membrane (or non-breathable + 25 mm cross-batten ventilation void). Klober Permo Air, Glidevale Protect VP400, Marley Eternit Universal — all common specifications.

Battens: BS 5534 grade-A battens (38 × 25 mm typical for tile-effect metal sheets at 600 mm rafter centres). Box-profile and standing-seam typically fix directly to purlins or solid decking with no batten layer.

Insulation: with the change in Approved Document L, most retrofits now require U-value ≤ 0.16 W/m²K — typically 150–200 mm of PIR (Celotex GA4000, Kingspan Therma TR26) between rafters plus a 25 mm cold-side over-rafter layer to break the thermal bridge.

Step 5 — Trim, ridge, and flashing

Metal roofing needs a full flashing kit:

Ridge cap along the full ridge length
Eaves trim (drip edge into the gutter): 2 × ridge length
Gable / rake trim: 4 × slope length on a duo-pitch
Valley flashing: V-section or open-valley metal where two pitches meet
Abutment flashing: where the roof meets a brick wall, chimney, or parapet — typically a soaker plus cover flashing chased into the brick joint

Budget 8–12% of the sheet cost for trims and accessories. Specify trims in matching colour and coating to the sheet.

Step 6 — Cost benchmarks (mainland UK, 2026)

For a 100 m² duo-pitch on a typical 1930s semi-detached house, NFRC 2026 contractor pricing (excludes scaffolding):

Specification	Installed total	Per m²	Notes
0.5 mm box-profile, 32/1000, PVF2	£5,500 – £7,500	£55 – £75	Cheapest, exposed fixings
0.5 mm tile-effect (Britmet Profile 49)	£7,500 – £10,500	£75 – £105	Tile look, fast install
0.5 mm standing-seam (Greencoat Urban)	£8,500 – £12,000	£85 – £120	Premium residential
0.7 mm zinc standing-seam	£12,000 – £18,000	£120 – £180	Architectural
0.7 mm natural copper	£20,000 – £26,000	£200 – £260	Heritage / high-end

Add scaffolding: typically £1,200 – £2,500 for a 4-week hire on a semi-detached house in southern England. Strip-off and skip: £900 – £1,800 depending on existing covering and skip permit.

VAT and grants

Most domestic re-roofing carries VAT at 20%. Reduced-rate (5%) applies if the property has been empty for 2+ years (HMRC Notice 708/6) or if the work is part of an energy-efficiency upgrade qualifying under VAT Notice 708/6 (insulation only, not the metal sheet itself). Check with your accountant.

Common UK mistakes this calculator avoids

Quoting roof area as the building footprint — undersizes sheet count by the slope factor (10–30%).
Forgetting the eaves overhang — typical 250–450 mm under BS 5534, adds 5–8% to material.
Ignoring the BBA Agrément certificate — building control will reject non-certified products.
Undersizing fixings — high-tensile steel screws to BS EN ISO 10666 with EPDM washers; stainless steel for coastal exposure.
Mixing aluminium and zinc fixings on a steel sheet — galvanic corrosion will eat the cheaper metal in 5–10 years.

For the cost-only view, see the metal roof cost calculator. To check your existing roof area, use the roof square footage calculator.

Sources

NFRC (National Federation of Roofing Contractors) Technical Bulletins 2024–2026; BS 5534:2014+A2:2018; BS EN 14782, BS EN 508-1/2/3; Approved Documents A, C, L (England, 2024 edition); BBA Agrément certificates for Tata Greencoat, Catnic Urban, Britmet; Cladco, Steadmans, and SIG Roofing trade-price lists 2026; Checkatrade and MyBuilder 2026 cost-by-trade reports.

Frequently asked questions

How do I work out how much metal roofing I need?

Multiply the slope-adjusted roof area (footprint × slope factor) and divide by the cover width of the sheet. UK box-profile sheets typically cover 1.0 m, standing-seam (Greencoat, Kingspan) covers 0.4–0.5 m, and traditional corrugated covers 0.76 m. Per slope, sheet count = ceil(eave length ÷ cover width). Add at least 5% for cuts and waste, 10% for hipped roofs.

What gauge of metal roof sheet should I specify?

UK steel sheets are typically 0.5 mm or 0.7 mm. 0.5 mm box-profile is the residential and agricultural standard. 0.7 mm is heavier and recommended for spans over 1.8 m or exposed coastal sites under BS EN 14782. Aluminium sheets are 0.7–0.9 mm. Standing-seam zinc and copper run 0.7–0.8 mm. Always check the manufacturer's loading tables against your purlin spacing.

How much does a metal roof cost in the UK?

Based on 2026 NFRC and Checkatrade data, expect £55–£85 per m² installed for box-profile steel, £85–£120 per m² for standing-seam steel (Greencoat, Catnic Urban), £120–£180 per m² for zinc, and £200–£260 per m² for natural copper. Tile-effect metal sheet (Britmet, Decra) lands at £75–£105 per m². These are mainland UK rates; Scotland and the South West run 5–10% higher.

Do I need planning permission for a metal roof in the UK?

Re-roofing with materials of similar appearance is normally permitted development (GPDO Class C) on a dwelling. A material change in appearance (e.g., from clay tiles to standing-seam steel) on a house in a conservation area, AONB, or listed building requires planning permission. Article 4 directions can also restrict re-roofing in some London boroughs. Always check with the local planning authority before specifying.

What underlay goes under a metal roof?

BS 5534:2014+A2:2018 requires a Type LR breathable membrane (e.g., Klober Permo Air, Glidevale Protect VP400) under battens for ventilated roof construction. Non-breathable underlay needs a 25 mm cross-batten void to BS 5250. For metal sheets fixed to solid decking, use a separation layer of high-temperature self-adhesive bitumen membrane to prevent contact corrosion between the decking and the sheet.

How long do metal roofs last in the UK climate?

PVF2 (PVDF) coated steel: 35–45 years; HPS200 Ultra coated steel: 40 years (Tata Steel warranty); zinc: 70+ years; copper: 100+ years; aluminium: 50+ years. Britmet and Decra stone-coated steel: 40 years. The PVF2 paint warranty (typically 30 years) usually expires before the substrate fails. Coastal exposure (within 1 km of saltwater) typically halves the warranty life — specify marine-grade coatings.

What's the minimum pitch for a metal roof in the UK?

BS 5534 and the manufacturer's literature govern. Box-profile and trapezoidal sheets are typically warranted down to 5° (1 in 12) with end-lap sealants and stitching screws; standing-seam to 3° (1 in 20). Below that, specify a flat-roof system (single-ply membrane, EPDM, mastic asphalt). Tile-effect metal sheets need 12° minimum to drain headlaps cleanly.

Metal Roof Calculator (UK)