Swapping a polycarbonate sheet is a repair. Putting a tiled, insulated roof on the same frame is something else, and the law treats it that way. Homebuilding & Renovating (guide updated July 2023) treats a solid roof in place of the original structure as material alteration work, and that puts it under the Building Regulations. You submit an application, and an inspector then checks what has been built.
What follows deals with the regulations only: what makes the roof notifiable, what the inspector checks, who that inspector is around Stroud, and how the paperwork ends. Planning permission is a separate question and has its own answer, whether a solid conservatory roof needs planning. The wider service is on our conservatory roof replacement page. Nothing here is legal advice, and your building control body has the final word on your own job.
Why a glazed roof and a solid roof are treated differently
The Building Regulations are about the performance of a building: whether it stands up, keeps heat in, drains, ventilates and is safe to be inside. Their reach depends on what the work does. A light glazed roof on a conservatory is a modest structure that is thermally separated from the house. A solid, insulated roof changes what the room is, and it changes the loads the frame has to carry.
Material alteration
That change is what material alteration means in practice. When a roof is replaced with a heavier, insulated construction, the building as altered has to meet the regulations for the parts that have been changed. For this reason a solid roof needs an application, where swapping a few worn sheets would not, and our guide on how a solid roof changes the status of the room picks up the wider consequences.
The Planning Portal's summary
The Planning Portal's FAQ on conservatory roofs gives the purpose of the rules in three parts: safe structure, energy performance and ventilation. That trio is a fair index to the rest of this guide: the frame and the load come first, then the insulation, then the air paths that keep the build-up dry.
One decision, several consequences
Once the roof is solid, the project has to be designed rather than ordered from a catalogue. The roofer needs the dimensions of the frame, the span, the pitch, the proposed covering and the build-up, and enough information for building control to judge them. That design information is part of the work whether or not anyone asks for it.
The structural check: can the frame carry it?
Of the three checks, the structural one is the one most often underestimated. Homebuilding points out that old polycarbonate frames now have to bear a roof of a different order. A tiled or slate roof with insulation and a plasterboard ceiling weighs a great deal more than twin-wall sheet.
What the weight rule says
On re-roofing, the Planning Portal ties approval to a covering that leaves the roof 15 per cent or more heavier, and Approved Document A calls a rise of more than 15 per cent a significant change in loading. The two wordings differ slightly, so for any job near the threshold the sensible step is to ask building control which applies. A solid roof on a conservatory is not a close call. It is far heavier than the glazing it replaces.
What the check looks at
The inspection covers the eaves beam, the rafters or steelwork, the connection to the house wall, the corner posts and the base, including the dwarf walls and foundations. Approved Document A adds that a structure which cannot take the extra load needs strengthening first. Our guide to conservatory frame checks goes through what we look at before we design anything.
Calculations and drawings
Where steel is introduced or the span is long, the building control body may ask for a structural engineer's calculations. Those are normally produced before the application goes in, so that the inspector sees a roof already designed to carry its load, not a promise to deal with it later.
The thermal check: insulation and the roof as a thermal element
The second check is about heat. A solid roof is built to keep warmth in, and the Building Regulations ask for evidence that it does. The standards sit in Approved Document L, the document on saving fuel and power. For a roof, the document measures performance by U-value, the rate of heat loss through a square metre of the construction for each degree of temperature difference. A lower U-value means less heat lost.
What we can and cannot say
The way Approved Document L applies to a conservatory depends on how the conservatory connects to the house, how much glazing it has and whether it is thermally separated from the main building. Which standard applies is for your building control body to decide from the plan. The thermal figure for a solid conservatory roof is therefore something we confirm with them for your own design.
Why separation matters
How far the room is closed off from the house, and how much of it is glazed, can change which energy standard the inspector applies. Opening the wall between the two is the kind of decision that alters the answer. It belongs with the choice to use the room all year, and it is worth settling with building control before the roof is designed.
Insulation in the build-up
Whatever the target, the roof build-up must show insulation of the right type and thickness, fitted without gaps. Our guide on insulating a conservatory roof compares the practical options. If the roof is being insulated as part of a home improvement, VAT Notice 708/6 treats installation of roof insulation in a home as zero-rated until 31 March 2027; your quote shows how VAT applies to your job.
Ventilation, drainage and the rest of the build-up
The third item on the Planning Portal's list is ventilation, and it is where a good roof design and a poor one differ most. Warm, moist air from inside a room finds its way into any gap in the ceiling and condenses on cold surfaces above. A roof that is insulated but not ventilated where it should be can collect moisture in the build-up, and the damage is out of sight until it has gone a long way.
Cold-roof ventilation
Marley's reading of BS 5250 (moisture in buildings) asks for a continuous eaves gap where a cold pitched roof is laid with a non-breathable underlay: 25 mm at pitches of 15 degrees or less, 10 mm above that. Roof pitches on conservatories are often low, so the low-pitch figure is common. The correct detail turns on underlay, covering and ceiling together, so it is written into the specification and not decided on the scaffold.
Rain and falls
The roof also has to shed water properly. That means the right minimum pitch for the covering, a flashing at the house wall and gutters and downpipes that take the run-off. Tile and slate coverings have a minimum pitch set by the manufacturer, and a low-pitched conservatory can rule out a heavy tile entirely, so the covering is chosen alongside the pitch. Our guide to conservatory roof options compares the coverings.
Fixings
Ridge and hip pieces on a tiled roof are mechanically fixed. BS 5534 changed in 2014 so that a bed of mortar cannot be the only thing holding them, and the inspector will want to see the screws or clips that secure them.
Who inspects the work around Stroud
You can use your council's building control or a registered building control approver, which is the private-sector option under the 2024 regulations. Which council applies depends on where the house stands.
| Where the house is | Council route |
|---|---|
| Stroud District | Gloucestershire Building Control Partnership, shared with Gloucester City |
| Gloucester City | Gloucestershire Building Control Partnership |
| Cheltenham or Tewkesbury | Cheltenham and Tewkesbury Building Control |
| Forest of Dean | The district council's own building control |
For Stroud District, the council's page explains that applications go through the partnership's site at gbcpartners.co.uk. The council says that a notification received before 3pm on a weekday is aimed at an inspection the following working day, where possible; that is a service aim, not a guarantee, so build slack into the programme.
Inspection stages
Inspectors usually visit at key points: before the structure is covered, at the insulation and ventilation stage, and at completion. They need to see the work before it is hidden behind the ceiling and the covering. If a stage is boxed in before the inspection, expect to be asked to open it up.
Cost of the application
The charge depends on the building control body and the scope of the work, so check the figure with your chosen body. It is an extra to the roof price, and the written quote allows for it, along with any engineer's fee. For the roof price itself, see our guide to conservatory roof replacement costs.
From application to completion certificate
On a solid conservatory roof job we explain the consent route at the survey, then handle the Building Regulations notification so that building control hears about the work before it starts. Plans, a specification and, where needed, structural calculations go with the application, so the inspector can judge the design before any timber is cut, and queries can be settled on paper rather than on a scaffold. The roofer then books inspections as the work progresses.
What you should receive
When the work is signed off, you should receive a completion certificate. It is the document that shows the roof was inspected and accepted, and it belongs with the other papers for the house. Buyers' solicitors and mortgage lenders may ask for it when the property is sold, and if the work was done without an application, regularisation after the event is slower and sometimes means opening up finished work.
DIY and unapproved work
Because the structural and thermal checks involve the frame and the build-up, self-built solid roofs are a particular risk when nobody has seen the work. Our answer on DIY conservatory roofs explains why.
What stays the same
Our 10-year workmanship guarantee is in writing, not insurance-backed, and we clear the site and remove the waste when finished. The quote is written to cover the application, any engineer's input, any reinforcement and the roof itself. To start, send us photographs of your conservatory inside and outside, with the approximate size, and we will plan a survey that looks at the frame first.