Common roof problems surveyors find

The roof problems surveyors find most often are slipped or missing slates and tiles, failing ridge and verge mortar, worn flashings around chimneys, ageing flat roofs, and issues in the loft such as condensation, decay or inadequate support. Most are routine maintenance items, but some, such as widespread nail sickness, a failed flat roof or a sagging structure, can mean a significant bill. Your survey should tell you which category your roof falls into.

Key points

• Surveyors normally inspect the roof from the ground and from inside the loft, not by climbing on it.
• Slipped slates, ridge mortar and flashings are common, usually affordable repairs.
• Widespread nail sickness or an old flat roof may mean replacement rather than repair.
• Problems in the roof space, such as decay or condensation, can be as important as the covering.
• Get a roofer's quote before exchange for anything rated condition rating 3.

How do surveyors inspect a roof?

In a Level 2 Home Survey or Level 3 Building Survey, the surveyor examines the roof covering from ground level, adjoining public areas and accessible windows, often using binoculars. Some surveyors use a camera on a pole or a drone where conditions allow. Inside, they inspect the roof space if there is safe access, looking at the timbers, underlay, insulation, ventilation and any signs of leaks.

A Level 3 survey usually involves a more detailed inspection of the roof space and a fuller explanation of the roof structure. For older or more complex roofs, that extra detail is often worth having. See Level 2 vs Level 3 for help choosing.

What are the most common roof problems?

Slipped, cracked or missing slates and tiles

The most common finding. Individual slipped or broken slates and tiles let water reach the underlay or roof timbers. Isolated repairs are cheap for a roofer, though scaffolding or access equipment can add to the cost.

Nail sickness on slate roofs

On older slate roofs, the iron nails holding the slates corrode over time. When many slates start slipping across a roof slope, the cause is often nail sickness. Patch repairs then become a losing battle, and the long-term fix is to strip the roof, replace battens and underlay, and re-lay the slates (reusing sound ones where possible) with new fixings.

Ridge, hip and verge mortar

Mortar bedding to ridge and hip tiles and along verges cracks and loosens with age and weather. Loose ridge tiles can be blown off in high winds. Rebedding or fitting a dry ridge or dry verge system is a common repair.

Chimneys and flashings

Chimney stacks are exposed and often neglected. Surveyors regularly flag:

• Leaning or cracked stacks.
• Eroded mortar joints and spalled bricks.
• Cracked or missing flaunching (the mortar around the pots).
• Worn or poorly fitted lead flashings where the stack meets the roof.

Defective flashings are a common cause of damp around chimney breasts. Our guide to damp in a survey covers how penetrating damp shows up inside.

Valley and parapet gutters

Valleys, where two roof slopes meet, and hidden parapet gutters carry a lot of water. If the lining is split or the gutter is blocked, water gets straight into the building. These are common problem areas on period terraces.

Flat roofs

Traditional felt flat roofs over extensions, dormers and garages often have a limited life, typically 10 to 20 years depending on quality and maintenance. Surveyors look for ponding water, blistering, splits and poor detailing at edges and upstands. Modern single-ply membranes, GRP (fibreglass) and EPDM rubber roofs can last longer if properly installed. If you are buying a house with an extension, see our extension and loft conversion survey guide.

What problems do surveyors find in the loft?

The roof space often tells the surveyor more than the outside.

• Missing or damaged underlay. Many older roofs have no underlay at all, which is not necessarily a defect but makes the roof less tolerant of slipped slates.
• Leaks and staining on timbers, often around chimneys, valleys and roof windows.
• Condensation. Poor ventilation, particularly where insulation has been packed tight to the eaves, can cause condensation, mould and eventually timber decay.
• Woodworm and decay in rafters, purlins and wall plates.
• Removed or altered timbers, for example where struts have been cut out to make storage space.
• Spray foam insulation, which can prevent inspection of the timbers and cause lending problems. See our guide to spray foam and cavity wall insulation.

Why do some roofs sag or spread?

Sagging rafters, a dipping ridge or walls pushed outwards at the top can have several causes:

• Heavier replacement covering. Many older houses originally roofed in slate were later re-covered with heavier concrete tiles without the structure being strengthened.
• Undersized or decayed timbers.
• Roof spread, where the rafters push the tops of the walls outwards because the roof is not adequately tied.
• Removed internal supports.

Slight undulation is common in older roofs and often long standing. Pronounced or recent movement needs investigating by a roofer or structural engineer.

Is asbestos ever found on roofs?

Yes. Corrugated asbestos cement sheets are common on older garages and outbuildings, and some artificial slates and soffit boards from before 2000 contain asbestos. Asbestos cement in good condition is generally low risk if left alone, but it needs specialist handling if removed. See our guide to asbestos in older homes.

What should you do if roof problems are found?

1. Check the condition rating. Condition rating 2 items are usually maintenance. Condition rating 3 needs urgent attention or investigation.
2. Ask the surveyor whether they think the roof needs repair or replacement.
3. Get a reputable roofer to inspect and quote before exchange.
4. Use the quote to renegotiate if the work is significant and not reflected in the price.

If you want a local surveyor to look at a roof before you commit, get a fixed-price survey booked and we will arrange access with the estate agent.

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