Learn the two Planning Portal tests, which council or private approver handles building control at your address, and the roof-related work that always needs approval, with the paperwork to ask for at the end.
Roof work in Kent sits under two separate sets of rules, and the two are easily confused. Planning permission is about how a building looks and what may be built. Building Regulations are about how the work is done: structure, fire, insulation and ventilation. A job can need one, both or neither, and this guide covers the second set.
The national test comes from the Planning Portal, and it leaves plenty of room for small repairs. Replacing a handful of slipped slates on a Margate terrace, or patching a flat roof over a back kitchen, usually sits comfortably inside it. Stripping and re-covering a whole roof does not, and neither does anything that adds weight, alters fire performance, or touches a chimney breast.
East Kent adds a local layer on top. The six councils across our patch, Ashford included, do not all run building control the same way and Dover words its rule more strictly than the national guidance does. Canterbury and Swale share STG. The sections below set out the tests, the councils and the work that always needs approval, so you can ask the right office the right question before a scaffold goes up.
The two tests the Planning Portal sets
The Planning Portal says no Building Regulations application is normally needed for re-roofing when two things are both true. First, "Less than 25 per cent of the total 'building envelope'" is affected, a measure that counts the whole shell of the house, including its roof windows and rooflights. Second, the work must touch less than 50 per cent of the roof.
The building envelope is everything that separates the inside of the house from the outside, so the first test is measured against the whole house. The second is measured against the roof alone. Both have to be met together, and passing one is not enough.
What that looks like on real jobs:
- A few replaced slates, a repaired valley or a new run of ridge sits inside both tests.
- Re-covering one small slope of a larger roof may sit inside them, depending on the size of the roof and the house.
- Stripping and re-covering every slope falls outside the 50 per cent test, so the route is checked with the council's building control team before the strip begins.
Notice what the tests leave out. They set no figure for Kent, and no council quoted in the third section publishes a percentage of its own. Where a council has a view, it says so on its own page, and the table in the third section shows each office. If your job is close to the line, a short call to the building control team for your address, with the survey photos to hand, settles it before any money changes hands.
Weight and fire performance of the new covering
Two further triggers apply whatever the percentages are. The Planning Portal requires approval when a new covering weighs at least 15 per cent more than the existing one, and when the new covering would behave significantly differently from the old one in a fire.
Approved Document A treats an increase in roof loading of more than 15% as a significant change. One document says 15 per cent or more and the other says more than 15%, so a figure close to the line should go to the council as a question, never be argued from memory.
On weight, the Planning Portal advises taking a structural engineer's or surveyor's view before work starts. A heavier covering puts more load on rafters, purlins and walls that were sized for the old one, so the survey looks at the timbers in the loft as well as the slope outside. Rafters in an older house can differ from one roof to the next, which is why a loft inspection beats a guess from the street.
Before you agree a change of covering, ask for:
- the weight per square metre of the old covering and the new one, from the makers' data sheets
- a note of what is under the covering, including rafter size and condition
- the fire performance of the new covering, as the maker states it
- the building control route for your address, in writing
A covering of the same kind as the old one sidesteps both triggers in most cases, and that is a fair reason to ask whether a repair or a like-for-like re-cover does the job before anyone prices a different material.
Which council handles building control at your address
Building control is not run the same way across the six districts we work in. Two of them share a service and the other four run their own, and the office that matters is set by the council your address sits in.
| Council | Handled by | Contact |
|---|---|---|
| Thanet | Its own team | 01843 577522 |
| Dover | Its own team | Via its building control page |
| Folkestone & Hythe | Its own team | 01303 853538 |
| Canterbury | The four-council partnership | STG Building Control, 01634 331133 |
| Swale | The same partnership (STG) | STG Building Control, 01634 331133 |
| Ashford | Its own team | Ashford Borough Council's Building Control |
STG's own page names four councils in its partnership: Canterbury, Gravesham, Medway and Swale. Canterbury City Council directs its applicants to STG for approval.
Thanet, Dover and Folkestone & Hythe each publish a service of their own, with no partnership stated, and Wye, Chilham, Challock and Brabourne go to Ashford Borough Council's own team.
For a Margate, Westgate, Broadstairs or Ramsgate address, the office is Thanet District Council's building control team at the Council Offices on Cecil Street, Margate. Folkestone & Hythe's team answers the phone between 10:00am and 4:00pm. Dover's page lists no phone number, so use the page itself and ask for the team by name. If you are unsure which council you are in, send us the postcode and we name the office before the survey.
The council also holds the register of completion certificates, and a copy from Thanet's register costs £54 including VAT, per Thanet District Council. That is worth knowing before you sell.
What each council's own page says about roof coverings
None of these council pages gives a percentage, but they differ in tone, and the differences matter.
- Thanet District Council has no re-roofing line of its own. It points readers to the Planning Portal and its Interactive House to check whether consent is needed, so Thanet addresses use the national test.
- Canterbury and Swale, through STG, set no re-roofing line of their own, so the Planning Portal test is the working guide there too.
- Folkestone & Hythe's page puts replacing roof coverings on a list of alterations that may need approval, and adds that the council does not require approval for the bulk of repairs, replacements and maintenance.
- Dover District Council's building control page includes re-covering pitched and flat roofs among the work it says needs approval, even a straight swap for the same material.
Of the pages quoted here, Dover's line is the strictest. Its list also covers new roof lights and loft conversions, so an owner there has more reasons to ask first.
Dover's wording applies to Dover District addresses only, such as Dover, Deal, Sandwich and the villages around them. A Margate or Ramsgate roof is judged on Thanet's route, and a Faversham roof on the Swale one.
Whichever address you have, we ask the office that holds it before the strip begins. The answer then comes from the right council and never from a neighbour who had work done across a district boundary. Council wording changes over time, so the page for your council on the day you book is the one that counts.
Roof-related work that always needs approval
Some jobs near the roof need Building Regulations approval whatever the percentages say. They can arise on any older Thanet house with a chimney, a loft or a rear addition.
| Work | What the rules say |
|---|---|
| Removing a chimney breast | The Planning Portal says approval always applies. |
| New roof windows | Approved Document L: Window Energy Rating Band B or 1.4 W/m²K. |
| New rooflights | Approved Document L: 2.2 W/m²K. |
| Solid conservatory roof | A new roof must comply; the small ground-level exemption does not cover it. |
| Loft conversion | Insulation, escape and stair rules apply; Dover lists all conversions. |
Where a chimney breast stands on a party wall, a second question follows, and it goes to a party wall surveyor, never to building control. Our guide to party wall notices for roof work covers the two months' notice.
A loft conversion on a two-storey house usually needs a protected stair, although Approved Document B allows an alternative escape route for the top storey.
For renovation work, Approved Document L (2021 edition) sets a roof threshold of 0.35 and an improved value of 0.16 in Table 4.3. Paragraph 4.13 relaxes that where upgrading is not feasible, or where a simple payback of 15 years or less is out of reach. Its renovation examples include a new waterproof membrane laid over a flat roof. A 2026 edition takes effect on 24 March 2027, so a job planned for next spring is worth checking against the version in force on its start date.
Council team or registered approver, and the paperwork
You are not limited to the council. A registered building control approver is the private alternative, and either route ends in the same place for you: someone independent has inspected the work and signed it off.
The regulations covering registration came into force on 6 April 2024, and GOV.UK says any private business wanting to do this work across England or Wales has to apply for registration with the Building Safety Regulator. Private building control existed before that date, under approved inspectors, so the registration is a change of rules and not the start of a new service.
Whichever route your job takes, agree three things before the strip begins:
- Which office is handling the job, with a name and a number to ring.
- When inspections are needed, so the roof is not covered over before someone has seen the timbers.
- What certificate you will receive at the end, and who sends it to you.
Keep that certificate with the house papers. A solicitor acting on a sale will ask to see it, and our note on the roof completion certificate says what to expect. Ask the approver or the council to confirm in writing which edition of the regulations applies to your start date.
The planning side has its own rules, set out in our guide to planning permission for roof work. Both sit under the wider range of roofing work across Thanet and East Kent that begins with a survey, photos of your own roof and one written total price.
