Stroud District has 41 conservation areas, and listed buildings are scattered through every valley, from mill cottages at Chalford to farmhouses above Painswick. Their roofs carry moss, lichen and algae like any other, but the margin for error is much smaller. A slate that cracks, an oak peg that snaps or a surface scoured pale is a loss of original material that cannot simply be bought back.
This guide explains the gentle methods we use on protected roofs, the tools we keep in the van, and the moments when it is worth ringing the council's conservation team. It is about the building's status. The material itself, stone and slate, is covered in our guide to cleaning stone and slate roofs, and the wider repair side sits under listed and conservation roofs. For the service as a whole, start at roof cleaning and moss removal.
What protection means for a roof clean
Whatever its grade, a listed building is covered in full, says Stroud District Council, from the front door to the back gutter. That takes in the slopes overhead. Section 7 of the 1990 listed buildings Act requires authorisation for works altering special character, and under section 9 proceeding without it is a criminal matter.
Cleaning sits in a grey area, and we do not pretend otherwise. Lifting a mat of moss with a soft brush is plainly maintenance. Stripping every trace of lichen from a medieval stone roof, spraying chemicals that stain the stone or applying a new coating could change how the roof looks and weathers. Whether a given job needs consent is for the council to say, not the contractor or the owner.
Listed, conservation area, or both
A conservation area is a different layer from listing. It covers a whole street or hamlet, and five of the district's areas, among them Bisley and Wotton Under Edge, carry Article 4 Directions withdrawing some permitted development rights. Whether roofs are covered is left open by the council, which suggests asking its planning department. Plain cleaning rarely hinges on it, but one call answers both questions.
Ring the conservation team before the work, not after. Keep their answer with your photographs.
The first visit: reading the roof before touching it
On a protected building the survey does more of the work than usual. We go up with the scaffold or ladder plan agreed and photograph the roof in sections, because those photographs are the record of what was there before cleaning started.
What we are looking for
- The covering. Cotswold stone slate, natural slate, handmade clay tile or an old pantile each tolerates different methods. A hand-made clay tile has a soft, porous face, and a stone slate may be delaminating in layers.
- The fixings. Stone slates are hung on oak pegs, and a peg that has dried and shrunk will not take much movement. Clay tiles are held by nibs and sometimes nails that have rusted.
- The growth. Moss is the main target. Lichen and algae are less simple, because on old stone they may be part of the roof's character, as discussed below.
- The lead and the mortar. Old flashings, soakers and lime mortar fillets are soft and easily damaged by a brush or a jet of water.
- Access. A listed cottage on a steep lane or a roof with no safe purchase may need a scaffold rather than ladders, and the quote allows for it.
Where a slate is already cracked, a peg has failed or a ridge has shifted, we mark it on the photographs and agree what happens next. Cleaning over a loose slate is how it ends up on the ground. Our guide to the roof cleaning process describes the sequence for a standard job, and a listed roof follows the same order with more stops for checking.
Gentle methods that suit old roofs
The principle is to use the lightest method that works and to stop as soon as the roof is clean enough to do its job.
Hand removal
Dry moss comes away best with a soft brush or a wooden or plastic scraper, working with the lap of the slate or tile and not against it. The idea is to lift the cushion away and leave the surface beneath alone. Cotswold District Council's 2000 stone slate guidance notes that a roof scraped yearly might last twice as long, so careful scraping is old-fashioned upkeep, not an intrusion. It is done kneeling on boards or crawling ladders that spread the load, because walking on stone slates breaks them.
Low-pressure water
Where growth is stubborn, a gentle rinse can follow the brushing. The jet is held well away and kept at low pressure, so it carries debris and does not drive water under the laps. The same care is needed with clay tiles, where a hard jet strips the fired surface and opens the pores to frost.
Biocide, used sparingly
A biocide is a liquid that kills growth so it stops returning. On a protected building it is applied by hand or low-pressure sprayer, in dry conditions, with the product chosen to avoid staining and with run-off kept away from planting and water. The effect is slow, and the dead growth falls away over the following weeks. The method is set out in our guide to soft washing and biocide treatments.
Methods kept off a protected roof
Much of the method is about what stays in the van.
- Pressure washing. A hard jet erodes the surface of stone and clay and forces water into joints. MyBuilder's 2026 cleaning guide flags the risk to delicate tiles. Our guide on why pressure washing damages roofs covers the risk in full.
- Wire brushes and scrapers with a hard edge. They gouge soft stone and leave bright marks that stand out for years.
- Strong acids and bleach. They etch limestone, discolour lead and kill the plants below.
- Sealants and coatings. A film over a breathable stone or clay surface can trap moisture, and once it is applied it is hard to reverse. English Heritage policy, reproduced by Cotswold District Council, calls modern substitutes unsuitable for historic buildings, and a coating departs further from the original.
- Walking directly on the covering. Boards and ladders go on first.
The lichen question
Lichen is a slow-growing partnership of fungus and algae that sits flat on the surface of stone. On a Cotswold roof it often gives the weathered, warm look people associate with age. Removing it entirely changes the roof's appearance, and it regrows slowly, so there is no urgency. Where lichen is not blocking water or lifting the surface, we usually discuss leaving it. Our note on lichen on roofs goes into this, and the conservation officer's view counts for more than ours.
When to talk to the conservation officer
The conservation officer is the council's specialist on historic buildings, and in Stroud District the contact is the planning and conservation team at the council offices. The conservation team can tell you whether an outbuilding next to a listed house shares its status; the same habit suits a roof clean when the position is unclear.
Cases where we would make the call
- The roof is of an unusual or early covering, such as thick stone slate with oak pegs, or handmade clay with visible wear.
- The growth is heavy enough that cleaning will reveal damage, so repairs are likely to follow.
- You want a biocide, a coating or any treatment that remains on the surface.
- The job needs scaffolding that attaches to or rests on the roof or the walls.
- The building sits in a conservation area with an Article 4 Direction.
What to have ready
The officer will want to know the building's address and listing grade if you have it, the roof covering, what you intend to do and how, and a photograph of the roof as it stands. The survey photographs we take are written for this purpose. A clear description of a hand-brush clean on a dry day is usually answered quickly.
Churches and chapels
A church still in worship use is exempt, and its roof work needs a faculty issued through the diocese. When worship stops, or a chapel is converted, the exemption goes and listed building consent normally comes from the council. A parish looking after its own roof should begin with its church buildings adviser.
Timing and the weather window
A protected roof is cleaned in settled weather. Wet slate and stone are slippery, damp lime mortar and old bedding are more easily disturbed, and a biocide applied before rain is wasted. We would rather move a visit than work in conditions that put the building at risk.
Season matters too. Brushing dry moss is far easier in a spell of dry weather than when the cushions are soaked, and a gentle treatment needs time to act before the weather turns. Frost is a particular worry for old clay and soft stone, because water held in a freshly rinsed surface expands as it freezes. Our guide to the best time of year to remove roof moss sets out the seasons, and on a listed roof we lean towards the drier, milder end of that range.
Nesting birds and bats
Protected buildings often house nesting birds and bats, which are legally protected. If we find either under the covering, the work stops in that area until you have advice.
Neighbours and access
Many protected houses stand in terraces or on narrow lanes where scaffold and ladders affect neighbours and passers-by. We plan this into the quote, as access on steep or narrow sites is worked out before the day and not found on it.
Cost, quote and aftercare for a protected roof
MyBuilder's 2026 roof cleaning guide gives national figures of about £400 to £750 for a tiled roof and £500 to £1,000 for slate, with manual scraping at £5 to £10 per m² and soft wash at £15 to £20 per m². These are national ranges, not Stroud prices, and hand methods, slower working and access planning tend to push a protected building towards the upper end. The quote after the survey itemises access, cleaning, any treatment and clear-up as separate lines.
Afterwards
When the work is done we photograph the same sections again so the record shows before and after. Bagged moss and other waste leave with us. The work carries a 10-year workmanship guarantee, in writing.
Keeping up with it
Light, regular attention is kinder than occasional heavy cleaning. A short yearly check from the ground, and a check of the gutters after leaf fall, will show whether growth is building. If it is, a hand clean every so often keeps the covering sound and the job small. A protected roof that is left until the growth is thick makes for the hardest and most expensive clean.
Photographs of your roof sent through the form or on WhatsApp are a good first step, and we can tell you from them how we would approach it and whether the council should be called first.