Quick answer: check your roof from the ground twice a year, in spring and autumn, and after any big storm. Clear gutters and valleys each autumn, deal with slipped tiles, damaged flashing and moss that blocks drainage, and keep flat roofs free of debris and standing water. When a flat roof starts to crack or leak, a liquid roof coating such as Aquaseal Liquid Roof can add a seamless waterproof layer, but only once the underlying problem has been put right.
In the UK, your roof takes a battering from rain, wind, frost and moss all year. Problems often go unnoticed until a leak appears inside. This guide from DIY Refurb covers how to identify your roof type, a practical maintenance checklist, winter preparation, moss removal, liquid roof coatings for flat roofs, and when to call a professional.
Quick Picks
- Emergency leak, wet weather: Evercryl One Coat
- Seamless flat roof overlay: Aquaseal Liquid Roof or Ultraflex Liquid Waterproofing
- New or replacement GRP fibreglass roof: Silverseel 600g GRP Roofing Kit
- GRP repairs and gutter leaks: Ultra V1 Waterproof Roofing Top Coat
- Moss and algae on tiles: Kingfisher Biocidal Wash
Quick Menu
- Pitched vs flat roofs
- Signs of roof damage
- Roof maintenance checklist
- Preparing your roof for winter
- Removing moss from roof tiles
- Flat roof maintenance and liquid roof coatings
- Roof type and product comparison
- How to apply roof coatings
- Safety and when to call a professional
- FAQs
Understanding Your Roof: Pitched vs Flat Roofs in the UK
The type of roof you have determines how you should maintain, repair and protect it.
Pitched Roofs
Pitched roofs are the most common on UK homes. Their slope sheds water quickly, and they are usually covered with:
- Clay tiles: traditional, long-lasting and breathable.
- Concrete tiles: durable and cost-effective.
- Natural slate: premium and very hard-wearing.
Common problems are cracked or slipped tiles, moss build-up, cracked ridge mortar and damaged flashing around chimneys and dormers.
Flat Roofs
Flat roofs are common on extensions, garages and dormers. They have only a slight fall and rely on a continuous waterproof layer, such as:
- Bitumen felt: popular and economical.
- EPDM rubber: flexible and long-lasting.
- GRP fibreglass: seamless and hard-wearing.
- Asphalt: traditional, often found on older roofs.
Flat roofs are especially vulnerable to ponding water, UV damage, blistering and splits at joints and upstands.
Signs of Roof Damage to Look Out For
- Cracked, slipped or missing tiles and slates.
- Loose or cracked ridge and hip tiles, or crumbling mortar.
- Lifted or split lead flashing around chimneys, walls and roof windows.
- Thick moss blocking valleys, gutters or tile channels.
- On flat roofs: blisters, cracks, splits at seams and water still sitting 48 hours after rain.
- Inside: damp patches or stains on ceilings, a musty loft, or daylight visible through the roof.
- Overflowing gutters or water running down walls.
Damp patches on top-floor ceilings or chimney breasts after rain often point to a roof or flashing problem. For more on damp, see our guide to damp and mould problems in lofts.
Roof Maintenance Checklist
Most roofing bodies recommend a visual check twice a year, in spring and autumn, and after severe storms. Do it from the ground with binoculars, or from a window. Don’t climb onto the roof.
| When | What to do |
|---|---|
| Spring | Look for storm and frost damage to tiles, ridges and flashing; check flat roofs for cracks and blisters; check for moss returning. |
| Autumn | Clear leaves from gutters, downpipes and valleys; cut back overhanging branches; check fascias, soffits and verges; clear flat roof debris. |
| After storms | Check for slipped tiles, lifted flashing and debris; look in the loft for damp or daylight. |
| Every few years | Have a roofer inspect up close, especially on older roofs or if you have noticed problems. |
Blocked gutters are one of the most common causes of damp walls and rotting fascias. See our guides to maintaining gutters, fascias and soffits and what to do if birds are nesting in your gutter.
Preparing Your Roof for Winter
November is a good time to get your roof ready before the worst weather arrives:
- Clear gutters and downpipes once most leaves have fallen, so water can drain away rather than freezing and overflowing.
- Fix slipped or broken tiles before winter winds get under them and lift more.
- Check flashing and seals: small gaps can be sealed with a lead-compatible sealant such as SX Lead Sheet Sealant, and exposed lead can be protected with Lead Flashing Paint.
- Clear flat roofs of leaves and moss, which hold water and speed up wear.
- Keep an emergency repair product handy: Evercryl One Coat can be applied to wet or damp surfaces and in temperatures down to −5°C, making it useful for winter leak repairs.
- Seal leaking gutter joints: Ultra V1 Waterproof Roofing Top Coat and Ultra V1 Roof Resin are single-pack, need no primer and are listed as suitable for gutter leaks; they can cure under 20mm of clean water.
- Check loft ventilation: make sure soffit and eaves vents aren’t blocked, to reduce condensation in the roof space. Push-in soffit vents can add ventilation to soffits.
How to Remove Moss from Roof Tiles
A little moss rarely harms a roof. It becomes a problem when it holds water against the tiles, blocks valleys and gutters, or lifts tile edges. To remove it:
- Use a biocide: apply a treatment such as Kingfisher Biocidal Wash on a dry day. Used without pressure washing, it is left for 7 days before brushing or gently hosing the surface clean.
- Avoid high-pressure washing: roofing bodies warn that it can erode concrete tiles, crack tiles and force water under the laps. If you must rinse, use low pressure and always spray down the slope, never upwards.
- Brush gently: scraping can damage tiles, so remove loose moss carefully from proper roof access equipment.
- Protect the surroundings: keep run-off away from plants, ponds and drains.
For other surfaces, see our guide to cleaning green algae from brick, render and concrete.
Flat Roof Maintenance and Liquid Roof Coatings
Keep flat roofs clear of debris, check them after heavy rain, and look for blisters, cracks and splits at joints and upstands. Small cracks can often be repaired; a roof that is widely cracked, spongy underfoot or leaking in several places may need replacing.
What Is a Liquid Roof Coating?
A liquid roof coating is brushed or rolled onto the existing roof and cures into a seamless waterproof membrane with no joints. It suits refurbishing sound but worn flat roofs, sealing details around upstands and outlets, and some pitched roof repairs.
Sika Everbuild Aquaseal Liquid Roof
Aquaseal Liquid Roof is a one-part, moisture-curing polyurethane membrane for flat and pitched roofs. Product details:
- Rain-resistant 10 minutes after application; fully cured in about 24 hours, depending on temperature.
- Bonds to concrete, bitumen, asphalt, felt, metal, tiles and timber.
- Coverage approx. 0.7kg/m² per coat, with two coats recommended. 7kg and 21kg tins.
- Apply at +5°C and rising.
- Can be reinforced with Sikalastic Roofing Fleece 120 over cracks, joints and details.
Ultraflex Liquid Waterproofing
Ultraflex Liquid Waterproofing is a single-component, ready-to-use liquid membrane in a 15kg tub, with no catalyst or hardener to mix. It bonds to most existing coverings, including old felt, asphalt, concrete and timber, so it suits refurbishment overlays. It is UV stable, trafficable 24 hours after application, and rated for up to 25 years when used with Ultraflex matting. For larger roofs, Ultra-Flex GRP kits can be applied direct to asphalt, concrete and metal without re-boarding, using wet-on-wet matting reinforcement.
GRP Fibreglass Roofing Systems
GRP is a cold-applied resin and glass-matting system that forms a seamless, hard-wearing roof, popular for extensions, garages and dormers.
- Silverseel 600g GRP Roofing Kit: BRoof(t4) fire rated, heavy-duty 600g chopped strand mat, suitable for foot-traffic areas, with a 20-year guarantee.
- Silverseel Fire Retardant Roofing Resin and Silverseel Fire Retardant Topcoat: used together, the system is certified to BS476 Part 3 FAB. Topcoat coverage approx. 500–600g/m²; catalyst supplied free.
- GRP Roofing Resin: cost-effective cold-applied resin for flat roofs, gulleys, garages, balconies and sheds, from 5kg to 20kg.
- Prymax GRP Primer: moisture-curing polyurethane primer that improves bonding of GRP to concrete, wood and metal, and can go on in damp (not wet) conditions.
- Topcoats: Topcoat White or Topfast RAL 9005 Jet Black, Lloyd’s approved polyester topcoats with free catalyst.
For repairs to existing GRP roofs, Ultra V1 Waterproof Roofing Top Coat is a single-pack, UV-curing top coat that needs no separate catalyst or primer and is listed to seal for up to 25 years.
Other Flat Roof Repair Options
- EVERBUILD Evercryl One Coat: fibre-reinforced, one-coat repair compound that can go on damp surfaces. Ideal for emergency patching.
- Roof Repair Coating (Low VOC): one-coat acrylic leak repair for felt, bitumen, asphalt and concrete.
- Black Bitumen Paint and Bostik All Weather Brush for bituminous surfaces.
Browse all our roof coatings. For outbuildings, see how to repair a leaking shed roof.
Roof Type and Product Comparison
| Roof type | Common materials | Typical issues | Products to consider |
|---|---|---|---|
| Pitched | Clay tiles, concrete tiles, natural slate | Cracked or slipped tiles, moss, flashing wear | Biocidal Wash, Kolourseal Roof Renovation, Lead Flashing Paint |
| Flat | Bitumen felt, EPDM, GRP, asphalt | Ponding, cracks, UV damage, blistering | Aquaseal Liquid Roof, Evercryl One Coat, Roof Repair Coating, Ultraflex |
| GRP fibreglass | Resin, glass matting and topcoat | Crazing, cracked topcoat, failed edge trims | Silverseel GRP kit, Prymax GRP Primer, Ultra V1 Top Coat |
| Asbestos cement sheets | Corrugated sheets on garages and outbuildings | Weathering, moss, brittleness | Asbestos Sealer & Primer, Asbestos Roof Coating. Never cut, drill or pressure wash; see our guide to asbestos sealers. |
How to Apply Roof Coatings
Preparation (All Roof Types)
- Repair first: replace broken tiles and fix splits and failed flashing. A coating won’t cure a structural fault.
- Clean the surface: remove moss, dirt and loose material with a stiff brush. Avoid high-pressure washing on tiles.
- Treat growth: apply a biocidal wash to kill moss, algae and lichen, allowing the drying time on the label.
- Check the weather: follow each product’s temperature range and rain-free period.
Coating Pitched Roof Tiles
Kolourseal Roof Renovation is a micro-porous acrylic coating for concrete tiles, clay tiles (excluding Rosemary), artificial slate and certain cement fibre sheets. It covers about 5–6m² per litre per coat, with two coats recommended, at +7°C to +35°C. Mask gutters and fascias first. Note that coating roof tiles may affect the tile manufacturer’s guarantee, so check before you start.
Coating Flat Roofs
- Stir the product thoroughly.
- Reinforce cracks, joints and upstands with fleece where the product allows.
- Apply by brush or roller, working from the far edge back towards your exit.
- Apply the number of coats and coverage rate stated on the product, without pooling.
Always follow the product label and technical data sheet.
Safety and When to Call a Professional
Falls from roofs and ladders cause serious injuries every year. Do as much as you can from the ground. Never walk on fragile roofs such as asbestos cement or plastic sheets, and avoid working at height alone or in wet, icy or windy weather. Call a qualified roofer for:
- Work above single-storey height, or anything needing scaffolding or crawl boards.
- Widespread slipped tiles, sagging, or structural concerns.
- Chimney, lead flashing or valley replacement.
- Flat roofs that are spongy, widely cracked or leaking in several places.
Roof Maintenance FAQs
How often should I have my roof inspected?
Check it yourself from the ground in spring and autumn and after storms. Have a roofer inspect it up close every few years, or sooner if you spot a problem.
Should I pressure wash moss off my roof?
Generally no. High pressure can erode and crack tiles and drive water under them. Use a biocide and gentle brushing instead, or low pressure directed down the slope.
Can I apply liquid roof coating in winter?
Check the product. Aquaseal Liquid Roof needs +5°C and rising, while Evercryl One Coat can be used on damp surfaces down to −5°C for emergency repairs.
Can a liquid roof coating fix a leaking flat roof?
It can seal a sound roof with minor cracks or worn areas, but the surface must be repaired, clean and prepared. Roofs with widespread damage or wet insulation usually need replacing.
Is GRP or a liquid membrane better for a flat roof?
GRP gives a very hard, rigid finish and suits new or re-boarded roofs. Single-component liquid membranes such as Ultraflex or Aquaseal are quicker for overlaying an existing sound roof. Check each system’s suitable substrates before choosing.
How long does a flat roof last?
It depends on the material, workmanship and maintenance. Regular clearing, prompt repairs and protective coatings all help extend its life.
