Across hundreds of roof surveys in Mid Sussex each year, we see the same core set of problems turning up again and again. Most of them are preventable with routine maintenance. All of them are cheaper to fix when caught early. None of them get better on their own.
This is the honest list of what we actually see most often – not a generic internet template, but the problems Mid Sussex roofers face week in and week out. If any of these sound like your roof, address them sooner rather than later.
1. Slipped and Broken Tiles or Slates
The single most common issue, responsible for more roof repair callouts than the next three problems combined.
What Causes It
- Nail failure – on Victorian slate roofs, the original iron nails rust and fail after 80-100 years. Slates then slip in clusters.
- Snapped nibs – the small hooks on the back of clay and concrete tiles that hook over the batten. These break with age, allowing tiles to slide.
- Storm damage – high winds on pre-2014 non-BS-5534-compliant roofs take tiles off in clusters.
- Impact damage – falling branches, foot traffic, aerial installation work all break tiles.
- Freeze-thaw spalling – older concrete tiles lose surface integrity and fragment.
When It Matters. One slipped tile in a storm is a repair. Multiple slipped tiles in ordinary weather suggests systemic failure and probably a re-tile rather than continuing repairs.
The Fix. Replace broken or slipped tiles with matching new or reclaimed tiles, mechanically fixed per BS 5534. See pitched roof re-tiling for when widespread repair becomes full re-tiling.
2. Roof Leaks and Water Ingress
Leaks show up inside the house before the external cause is obvious. By the time a ceiling stain appears, water has usually been tracking through the roof structure for weeks or months. Spotting early signs of roof damage from the ground and the loft catches problems before they reach the ceiling.
What Causes It
- Failed flashings around chimneys, abutments, and dormers (the most common specific leak source)
- Gaps in the underlay from age or physical damage
- Slipped tiles creating a direct water path
- Valley damage
- Ridge mortar failure on older roofs
- Blocked gutters overflowing behind fascias
Detection. From inside: water staining on ceilings (usually rooms on top floor), damp patches on chimney breast walls, water drips visible during rain in the loft, mould spots on rafters. From outside: running water on walls after rain, missing or displaced tiles visible, lifted flashings.
The Fix. Diagnosis first, repair second. Tracing a leak from the visible symptom back to the cause often requires a proper roof inspection. See whether to repair or replace your roof and emergency roof repair in Sussex.
3. Flashing Failure
Chimney flashings and wall abutment flashings are the most common specific leak source on any Sussex roof over 20 years old.
What Causes It
- Lead lifting from its chase (insufficient original chase depth, failed wedging)
- Mortar pointing failing around the lead
- Lead fatigue cracks from thermal movement
- Storm damage lifting flashings
- Chimney or wall movement stressing the flashing
The Fix. Professional leadwork – re-dressing the lead, re-chasing where needed, new wedging and pointing. See leadwork roofing guide and lead flashing and valleys.
4. Flat Roof Problems
On extensions, garages, dormers, and porches with flat roof sections, the problems are different from pitched roofs.
What Causes It
- UV degradation of the membrane (EPDM, felt, GRP)
- Thermal movement cracking at upstands and laps
- Ponding water (inadequate fall during installation)
- Failed flashings at upstands and abutments
- Physical damage to the membrane
Signs. Standing water remaining 48+ hours after rain, cracks/splits/blistering of the membrane, ceiling stains inside under flat-roofed sections, visible deformation of insulation beneath.
The Fix. Depending on extent: patch repair, localised membrane replacement, or full re-cover. See flat roof repair guide and when to replace your flat roof.
5. Moss, Algae, and Biological Growth
Sussex’s damp climate, particularly in wooded Weald villages, promotes moss and algal growth on roof surfaces.
What Causes It
- North-facing slopes stay damp longer and develop moss faster
- Heavy tree cover holds moisture and deposits spores
- Older concrete tiles lose their coating and become porous, retaining water
- Ridge and verge mortar provides a hospitable surface for lichen
Why It Matters. Moss isn’t inherently destructive, but it retains water against the tile surface (accelerating freeze-thaw damage), traps roof debris, adds significant weight to the roof when wet, masks underlying tile damage from inspection, and washes into gutters creating blockages below.
The Fix. Manual removal (not pressure washing, which damages tiles). Biocide treatment prevents regrowth for 3-5 years. Addressing the root causes – trimming overhanging trees, improving drainage – extends the effect.
6. Structural Issues
Sagging or visibly distorted roof lines indicate structural problems rather than covering issues.
What Causes It
- Rotten rafters or purlins from sustained water ingress
- Failed ceiling joists or ties
- Overloading from a tile upgrade the structure wasn’t designed for (concrete tiles on a roof built for slate, for example)
- Historical storm damage that was never properly addressed
- Settlement or foundation movement affecting the whole roof structure
Detection. From the ground: visibly wavy ridge line (should be straight), sections of the roof slope that are bowed or concave, gable wall bowing outwards. From the loft: rafters visibly sagging or split, purlins cracked or deflecting, ceiling joists showing excessive movement.
The Fix. Structural engineer’s assessment. Depending on findings: reinforcement of existing timbers, replacement of failed members, or in severe cases full re-roof with new structure.
See signs for replacing a pitched roof.
7. Poor Ventilation and Condensation
The hidden problem that rots Sussex roofs from the inside.
What Causes It
- Inadequate eaves ventilation (insulation blocking the air path at the eaves)
- No ridge ventilation on modern-build warm-moist-climate construction
- Old impermeable underlay trapping moisture
- Vapour barrier missing or damaged on warm-roof constructions
- Increased moisture loading from modern living (showers, driers, indoor plants)
Signs. Condensation drips visible in the loft, black mould spots on rafters and joists (particularly near the ridge and on north slopes), damp insulation at the eaves, musty smell in the loft.
The Fix. Adding or improving ventilation at the eaves and ridge. Replacing impermeable underlay during re-roof work. In severe cases, reconstructing the roof build-up to correct BS 5250 compliance.
See pitched roof ventilation and insulation.
How Sussex Conditions Drive These Issues
Rain and Freeze-Thaw. Mid Sussex’s 800-850mm annual rainfall combined with January-February freeze-thaw cycles is particularly hard on porous materials (older concrete tiles, mortar, timber fascias). Most of the issues above accelerate in late winter when freeze-thaw damage compounds existing wear.
Wind and Named Storms. Every named Atlantic storm that passes over Sussex stresses the roof system. Storms Eunice (2022), Ciaran (2023), and Henk (2024) each caused significant damage across Mid Sussex. Cumulative storm damage on pre-2014 roofs with mortar-only ridges accelerates all the above issues.
Tree Cover. Wooded Weald villages (Cuckfield, Lindfield, West Hoathly, Ardingly, Balcombe) see faster development of moss, algae, gutter blockage, and consequent roof issues than more open inland positions.
Prevention – What Actually Works
Most of these issues are preventable or significantly delayable with routine maintenance:
- Twice-yearly gutter clears (spring and autumn) – prevents 40-50% of water-related issues
- Annual ground-level visual inspection – catches issues in weeks 1-2, not years 2-3
- Professional survey every 3-5 years – finds what you can’t see from the ground
- Post-storm checks – catches storm damage before it compounds
- Tree trimming – reduces both moss and gutter blockage
- BS 5534 upgrade for pre-2014 roofs – converts a fragile roof to a storm-resistant one
See pitched roof maintenance for the full schedule.
When to Call a Professional
Any of these issues warrant a professional look:
- Active water ingress
- Structural sagging or movement
- Flashing failure or repeated leaks despite repairs
- Multiple slipped tiles after ordinary weather
- Condensation issues in the loft
- Storm damage of any kind
Small issues with cheap fixes become expensive with delay. Our survey is free and our assessment is honest – we tell you what actually needs doing, not what we’d like to sell you.