When Does Roofing Work Need Building Control? A Job-by-Job Guide

Quick Answer: Most roof repair work is non-notifiable, but any work affecting structure, thermal performance, fire safety or significant change of construction is notifiable to building control under the Building Regulations 2010. The triggers are: re-roofing more than 25% of a roof slope, structural alterations (new roof structure, dormer additions, removed chimney breasts), thermal upgrade (changed U-value), changed roof shape, conversions of unheated to habitable space (loft conversions), and any work to flat roofs that involves new construction. Notifying via Approved Inspector or Local Authority Building Control before starting work is mandatory; retrospective notification is heavily penalised.

Summary

Roofing work spans the spectrum from completely non-notifiable (replace 5 broken tiles) to fully notifiable with extensive inspection requirements (full re-roof with thermal upgrade and changed roof structure). Tradespeople need to know which work falls into which category to:

• Quote correctly (notifiable work needs building control fees and inspection time)
• Programme correctly (inspections take days, not minutes)
• Stay legally compliant (skipping notification on notifiable work is a regulatory offence with potential 2-year prosecution window)
• Protect the homeowner (a sale-day finding of unnotified work means an indemnity policy purchase or remedial notification at high cost)

The 25% threshold is the key UK rule: re-roofing more than 25% of a single roof slope (or thermal upgrade exceeding 25% of the slope area) makes the work notifiable. Below 25%, it's typically maintenance and non-notifiable. Crossing the 25% threshold without notifying is the most common quote-stage compliance error.

This article maps out every common roofing job to its notification status, helps quote the correct fee, and outlines the inspection sequence so contractors plan around it. For UK roofing work specifically, the rule of thumb is "if in doubt, notify" — the cost of notification is small (£100-£500) compared to the cost of remediating unnotified work later.

Key Facts

• 25% rule — re-roofing or thermally upgrading more than 25% of a roof slope is notifiable
• Like-for-like repair — non-notifiable; matching tile replacement, patching, gutter swap
• New construction (re-roof, new roof, dormer) — always notifiable
• Flat roof construction or replacement — notifiable
• Loft conversion — always notifiable (Part B fire, Part L thermal, Part K stair, Part F ventilation)
• Approved Document L applies on re-roof — U-value 0.16-0.18 W/m²K target if upgrading
• Approved Document B applies on loft conversion — fire safety, escape stair, fire doors
• Approved Document A applies on structural changes — new ridge, hip, valley, removed bracing
• Notification fee — full plans submission — £400-£1,500 typical depending on project
• Notification fee — building notice — £200-£800 typical
• Inspection visits per project — typically 3-6 for a re-roof, 5-8 for a loft conversion
• Approved Inspectors vs Local Authority — both options; AIs typically faster, sometimes more expensive
• Penalty for failure to notify — prosecution within 2 years of work; daily fines
• Standard — Building Regulations 2010 (England and Wales); separate regimes in Scotland and Northern Ireland

Quick Reference Table

Detailed Guidance

The 25% Rule Explained

The 25% rule is the central trigger for re-roofing notification. From Approved Document L:

"Where the work consists of substantial replacement of a roof covering — work to more than 25 per cent of the area of the roof — and where the roof is part of a thermal element, then the thermal performance of the roof should be improved to comply with the standards in Table 4.4."

In plain English: if you're stripping more than 25% of a single roof slope, you must thermally upgrade that area to current Part L standards (0.18 W/m²K typically). And the work becomes notifiable.

Examples:

• A 50 m² roof slope with 13 m² (26%) of damaged tiles being replaced → triggers the 25% rule. Notifiable. Thermal upgrade required at the same time.
• The same 50 m² with 12 m² (24%) being replaced → not notifiable. No thermal upgrade required (though good practice).
• Two separate slopes on the same roof, each 30% replaced → each slope is assessed individually. Both notifiable; both need thermal upgrade.

For practical purposes: if the area being replaced is "comfortably more than a quarter," assume notifiable.

Like-for-Like vs Substantial Replacement

Like-for-like repair — replacing damaged elements with matching new ones, no change to roof shape, structure, or thermal performance:

• Replacing 5-15 broken tiles with matching tiles: not notifiable
• Repointing ridge tiles: not notifiable
• Replacing one missing slate: not notifiable
• Patch-replacing felt under a tile: not notifiable

Substantial replacement — affecting structure, U-value, fire performance, or roof shape:

• Re-roofing more than 25% of a slope: notifiable (25% rule)
• Adding a dormer or rooflight that changes the roof line: notifiable
• Replacing roof timbers (rafters, purlins, ridge): notifiable
• Adding insulation that brings the roof from cold to thermally compliant: notifiable
• Converting a loft to habitable room: notifiable

Loft Conversions: The Most Heavily Notifiable Job

Loft conversions touch almost every Approved Document:

• Part A (Structure): new floor structure, new dormer or roof opening, possibly new beams
• Part B (Fire safety): protected stair, fire door at base of stair, smoke detection, fire-rated separation, escape route
• Part C (Moisture): roof and wall weather resistance
• Part E (Sound): separating floor sound insulation
• Part F (Ventilation): extract from bathroom, background ventilation
• Part K (Stairs): stair pitch, headroom, balustrade
• Part L (Thermal): roof insulation, wall insulation if applicable

Notification typically requires full plans submission rather than building notice for loft conversions because of the complexity of the regulations. Inspection sequence is detailed — typically 5-8 visits over 4-12 weeks.

Flat Roof Notification

Replacing a flat roof covering like-for-like (same construction type, same U-value, same falls) is non-notifiable.

Replacing the flat roof construction (e.g. converting cold-deck to warm-deck) is notifiable because the U-value improves and the construction changes.

New flat roof on an extension is part of the extension notification and follows the extension notification rules.

Solar PV: Notification Status

Adding solar PV to an existing roof:

• Tile-on-tile system (panels mounted over existing roof covering) — usually non-notifiable, but check with local authority. Some councils require notification for any roof loading change.
• Integrated system (replaces tiles with PV-integrated tiles) — notifiable as a re-roofing element (25% rule)
• Roof-integrated PV (in-roof system) — notifiable; counts as roof construction
• Structural impact (PV array on weak roof structure requiring reinforcement) — notifiable for structural work

For anything beyond a simple over-tile install, notify.

Approved Inspector vs Local Authority

Two notification routes exist:

Local Authority Building Control (LABC) — the council's own building control team. Statutory body. Sometimes slower; sometimes more risk-averse interpretation.

Approved Inspector (AI) — private companies licensed to provide building control services. Often faster, more flexible scheduling, sometimes specialise in particular work types. Slightly more expensive.

For typical residential roofing work, both routes work the same. AI may be preferable for time-critical projects or those needing specialist knowledge (e.g. listed buildings, complex thermal calculations).

The notification fee is typically £200-£600 for typical roofing work either route; loft conversions £800-£2,000 either route.

What Happens When You Don't Notify

The Building Regulations 2010 (Section 35-39) carry two routes for unnotified work:

Prosecution — within 2 years of work completion, the local authority can prosecute. Maximum fine £5,000 for each offence plus £50 per day continuing offence. Director liability for limited companies.

Section 36 enforcement — can require demolition or rectification of non-compliant work. Cost falls on the building owner; contractor liable in tort.

Sale-day discovery — solicitor checks reveal no completion certificate. Buyer's solicitor demands certificate. Three options: retrospective notification (often refused), indemnity policy (£100-£300, but doesn't cover pre-existing defects), demolition and rebuild (rare but happens for serious cases).

For a builder, unnotified work is:

• A regulatory risk
• A reputation risk if the homeowner can't sell
• A financial risk on a future warranty claim or insurance issue

Inspection Sequence

For a typical re-roof requiring building control:

1. Notification submission — drawings, scope, calculations
2. Acceptance / queries — typically 3-10 working days
3. Inspection 1: Strip-out — once existing covering removed, before insulation laid. Inspector checks deck condition, structural integrity, condition before continuing.
4. Inspection 2: Insulation + VCL — installed but before deck/membrane goes on. Inspector measures insulation thickness, checks VCL detailing, photographs.
5. Inspection 3: Pre-membrane — membrane to be laid that day or following. Inspector checks deck, thermal continuity.
6. Inspection 4 (if applicable): Detailing — parapets, abutments, rooflight upstands.
7. Final inspection — completion. Inspector confirms work matches drawings, photos, calculations. Issues completion certificate.

For a loft conversion:

1-2. As above plus pre-strip-out structural inspection 3. Floor structure (new joists, beams) 4. Insulation in roof and walls 5. Stair installation (Part K dimensions) 6. Fire-stop installation, fire door, smoke detection 7. Final inspection, EPC, completion certificate

Quote Stage: Notification as a Cost Line

A clean quote includes:

• "Building Control notification: £350 (paid to Local Authority / Approved Inspector by client direct, or included in our charge)"
• Programme allows for notification time (1-2 weeks before site start)
• Programme allows for inspection visit (typically half-day to one day during work)
• Final completion certificate is a deliverable to the client

Quoting "We'll handle building control" without listing the fee is sloppy. Quoting "Don't worry about building control, the council won't know" is grounds to refuse the work.

Programme Implications

For a small re-roof (one slope, 30 m²):

• Notification + acceptance: 1-2 weeks
• Strip-out and inspection 1: day 1, plus inspector visit
• Insulation + inspection 2: day 2-3, plus inspector visit
• Membrane and tile lay: days 3-5
• Final inspection: day 5-6, plus inspector visit
• Total programme: 1-2 weeks, with 3 inspector visits

For a loft conversion:

• Notification + acceptance: 4-8 weeks
• Site work: 6-12 weeks with 5-8 inspections
• Final certification: 1-2 weeks after completion
• Total programme: 12-24 weeks

These programme realities mean quoted dates should be conservative when notification is involved.

Frequently Asked Questions

Is a Velux window installation notifiable?

A standard Velux replacing an existing rooflight (or in non-habitable space): not notifiable.

A Velux above 0.25 m² in a habitable conversion (loft conversion bedroom): notifiable as part of the conversion notification.

A new rooflight cut into a previously closed roof (creating an opening): structurally notifiable, and notifiable for thermal performance if it affects U-value.

Do I need building control for a chimney removal?

Yes. Chimney removal is structural — it affects the load path. Notifiable under Approved Document A. Even removing the chimney breast in a loft (where the stack continues but the breast goes) is notifiable because it affects the structural support to the breast above.

What about a like-for-like flat roof re-cover?

Like-for-like re-cover (same membrane type, same insulation, same construction) is non-notifiable. The moment you change anything (new insulation, different membrane type, new falls), it becomes notifiable.

Can I just add insulation under an existing pitched roof without notification?

Adding insulation to an existing pitched roof (between rafters or above rafters) is notifiable under Part L because U-value changes. Even if no other work is done, the thermal upgrade triggers notification.

How do I find out if work was previously notified?

Local authority property records — check at the council's planning portal (most have online searches). Building control records may also be searchable. For private homeowners checking before buying, the seller should provide all completion certificates. Missing certificates indicate either non-notifiable or unnotified work.

Regulations & Standards

• Building Regulations 2010 — primary legislation; sets notification requirements

• Approved Document A — Structure

• Approved Document B — Fire safety

• Approved Document C — Site preparation and resistance to moisture

• Approved Document E — Resistance to passage of sound

• Approved Document F — Ventilation

• Approved Document K — Protection from falling, collision and impact (stairs)

• Approved Document L — Conservation of fuel and power

• Building (Approved Inspectors etc.) Regulations 2010 — Approved Inspector framework

• Local Authority Building Control (LABC) — published guidance — practical notification guidance per council

• NHBC Standards — warranty-spec work (overlaps with building control but separate scheme)

• Building Regulations — gov.uk — current Approved Documents

• LABC — Local Authority Building Control — local notification guidance

• Approved Inspectors — list — registered AIs

• Building Regulations 2010 — legislation — primary statute

• NHBC — building regulations — warranty-spec compliance

• [Council planning portals — search by postcode] — historical building control records

• building control: approved inspector vs local authority — choosing notification route

• competent person schemes — when notification is via certified contractor

• flat roof Part C compliance — moisture resistance specifically

• flat roof Part L compliance — thermal performance

• loft conversion pricing — building control fees in context