Reviewed, sourced guidance

Choose a roof tile waste allowance

Published 24 Sept 2026Reviewed 25 Sept 20261 min read

Direct answer

There is no single waste percentage that fits every roof. UK calculator competitors suggest different starting ranges for simple gables and cut-up roofs, but those are estimates, not a universal manufacturer rule.

Waste depends on roof geometry, cuts, openings, tile format and the ordering plan. This calculator leaves the allowance to the user.

Key takeaways

Hips, valleys and dormers create more cuts than uninterrupted planes.
Tile format and layout influence offcuts.
A generic calculator percentage is not a product specification.
Keep repair spares separate from cutting waste.

Evidence note

Source-led homeowner information with its scope, limits and commercial status recorded.

View the full evidence note

Produced by: My Roofing Calculator
Jurisdiction: UK-focused measurement information; permissions and building-control requirements are not assessed.
Page scope: Factors to review before entering a project-specific tile allowance.
Default subject: Pitched roof area, product-based quantity estimates, roof pitch and comparable quote scope.
Excludes: Roof inspection, survey or access planning; Structural, engineering or installation advice; Product selection or manufacturer endorsement; Contractor recommendation, ranking, referral or lead collection; Roofing work, quotations or guaranteed material quantities
Published: 2026-09-24
Reviewed: 2026-09-25
Commercial status: Information preview only. No roofing contractor is active, no lead capture runs, no enquiries are collected and no affiliate links are present.

This guide does not prescribe a percentage or replace a roofer’s measured take-off.

How this guidance is produced · Correction submission status

Check what changes the cut pattern

A simple rectangular plane and a roof with hips, valleys, dormers or rooflights do not create the same cutting pattern.

Cushty’s UK tools offer shape-based suggestions, while also warning that complex roofs need plane-by-plane measurement and judgement.

List every hip, valley, verge and opening.
Note tile size, bond and whether courses align at edges.
Ask the installer which cuts and spares their allowance covers.

Sources for this section: Cushty, Roof Area Calculator UK (observed 2026-09-25)Cushty, Roof Tile Calculator UK (observed 2026-09-25)

Choose and label the allowance

Some competitor calculators suggest about five per cent on a simple gable and higher ranges for hips, valleys or cut-up roofs.

Those are the competitor’s planning suggestions. They are not a guarantee for your roof or a substitute for a system take-off.

Enter the chosen percentage explicitly rather than accepting a hidden default.
Keep net tiles and allowance-adjusted tiles visible as separate figures.
Confirm whether spares for future repairs are additional.

Sources for this section: Cushty, Roof Tile Calculator UK (observed 2026-09-25)

Reduce avoidable reordering

Before ordering, confirm the exact product and finish with the supplier. Ask about current stock, batch consistency, spare quantities and return terms.

Have the final quantities checked against the roof survey, drawings and manufacturer guidance.

Record the source and date for each coverage rate.
Do not use waste to disguise uncertain measurements.
Ask the supplier how unopened packs and damaged deliveries are handled.

Sources for this section: Cushty, Roof Tile Calculator UK (observed 2026-09-25)

Next steps

Set the allowance only after listing roof details and cuts.
Keep the allowance separate from fitting quantities.

Sources

Use the measuring checklist