What Does a Surveyor Look for When Inspecting a Roof?

The roof is, arguably, the most important single element of any building. It protects everything beneath it from the elements. When it fails, the consequences cascade downwards — through the loft, into the ceilings, down the walls and into the very fabric of the building. And roof repairs are expensive. Very expensive.

In every building survey I carry out, the roof inspection is the section I spend the most time on. Here is exactly what I look at — and the warning signs that any buyer can spot before they even pick up the phone to us.

External Roof Inspection: What We Look For

Pitched Roofs (Slates and Tiles)

• Missing, slipped or cracked slates/tiles — the most obvious sign of roof distress. Even one missing slate can allow significant water ingress.
• Ridge tiles — the capping along the apex of the roof. Loose or failed ridge tiles are a common finding and can be dislodged by wind.
• Flashings — metal (usually lead) strips that weatherproof the junctions between the roof and chimneys, dormers and walls. Failed flashings are the single most common cause of roof-related damp.
• Valleys — the internal angular junction where two roof slopes meet. Lead valleys are frequently found to have failed, cracked or been poorly repaired in older properties.
• Chimney stacks — examined for defective pointing, cracks in the brickwork and loose or missing lead flashings at the base. Chimney stacks are a notorious entry point for water.
• Gutters and rainwater goods — blocked, sagging, cracked or overflowing gutters cause damp to the walls below. Blocked hoppers and downpipes are among the most common maintenance failures I find.

Flat Roofs

Flat roofs (typically over extensions, bays and garages) require particular attention:

• Ponding water — water that doesn't drain away indicates poor falls and can accelerate deterioration
• Cracked, blistered or delaminating felt or asphalt covering
• Upstand and parapet detailing — where the flat roof meets a wall is the most common point of failure
• Roof lights and skylights — checking for failed seals and condensation between the panes

Loft / Internal Roof Inspection

Where a loft hatch is accessible, I will always inspect the internal roof structure. This reveals information that no external inspection can provide:

• Roof timbers — checking for deflection (sagging), splits, damage, woodworm bore holes and fungal attack
• Evidence of water ingress — staining on the underside of the sarking felt or on the roof timbers is a tell-tale sign of a leak
• Insulation — checking that adequate insulation is present to modern standards (100mm between joists plus 270mm above is current guidance)
• Ventilation — adequate roof ventilation prevents condensation build-up in the loft space, which can cause timber decay
• Party wall conditions — in terraced properties, the loft inspection includes checking the condition of any party wall in the roof space

How Much Do Roof Repairs Cost?

• Isolated slate/tile replacement: £200–£600
• Ridge tile repointing: £500–£1,500
• Lead flashing replacement: £800–£3,000 (depending on extent)
• Full re-roof (3-bed terrace): £8,000–£18,000
• Flat roof replacement: £1,500–£6,000 (depending on area)
• Chimney stack full rebuild: £3,000–£8,000

Warning Signs to Look for Yourself at a Viewing

Before you even commission a survey, there are things you can look for during a property viewing:

• Look up at the roof from the street — any visibly sagging, missing or uneven tiles?
• Check gutters — are they pulling away from the fascia, overflowing (shown by green staining below) or visibly blocked?
• Look at the chimney stacks — any visible cracks or missing mortar?
• Inside the property, look at the top-floor ceilings — any damp staining, tide marks or fresh plasterwork that might conceal a leak?
• If possible, look into the loft — any daylight coming through, signs of damp or debris from fallen plaster?

"The roof tells you more about the true age and condition of a property than almost anything else. I've walked into 'recently renovated' houses and found roofs that haven't been touched in 40 years." — Marcus Osei