Decide whether the symptom belongs to the tiled covering
Cracked, displaced or missing tiles, loose ridge or hip units, mortar debris and roof-void daylight justify assessment. Damp does not prove the tile above has failed: water can enter at a valley, flashing, verge or penetration and travel along underlay.
Decide whether the concern is isolated, repeated or storm-linked. A loose unit above an entrance or exposed opening needs urgent risk review; stable weathering can follow a planned route. Moss or colour change alone does not prove replacement is needed.
Diagnose the tile, fixing and underlay condition
Identify the tile family, profile, clay or concrete material, fixing and interlock. Record cracks, chips, displacement, weathering and incompatible replacements. Ridges, hips, verges and eaves need their own observations rather than one tile-condition label.
Visible underlay, battens and roof-void evidence show whether a defect remains local. Tears, staining, decayed support or daylight may change scope, while concealed construction needs access or agreed opening-up. Compare leak timing with valleys, abutments, chimneys and roof windows.
Compare isolated replacement with wider tile renewal
An isolated repair replaces compatible units and corrects a local fixing or junction while retaining sound work. It should explain protection of adjoining tiles and matching supply. Local repair is weaker where neighbours are brittle or substitutions no longer interlock.
Wider renewal may suit failing tiles, battens or fixings across a slope, inaccessible underlay work or repeated incoherent repairs. Review ridge, hip and verge methods too. The recommendation should follow defect distribution, not age alone.
Match profile and specification, not just colour
A replacement must fit the gauge, headlap, side interlock and fixing. Manufacturer marks, dimensions, nibs, profile and material matter more than colour where a line is discontinued or weathered. A poor fit can admit wind-driven rain.
Clay plain tiles, concrete interlocking units and other systems differ. Pitch, exposure and laying pattern matter in a broader specification. Listed or conservation context may limit material or appearance changes, so seek local authority advice before substitution where relevant.
Inspect every junction that interrupts the tile field
Valleys, abutments, chimneys, roof windows, vents and level changes interrupt the tile pattern. Examine flashing, mortar, soakers and surrounding units together. Valley or gutter debris can alter flow without a defective tile.
Ridges, hips, verges and eaves finish the system edges. Distinguish tile replacement from mortar or mechanical-fixing work, and note gutters, fascias or flat-roof junctions that contribute. Keep trade boundaries explicit.
Prepare roof-void and ground access
Safe roof-void access can show staining, daylight, underlay and penetrations, but enter only where flooring, lighting and structure permit. Provide ground-level images and identification from spare tiles or records. Do not lift tiles or walk the roof.
Mention height, pitch, lower roofs, narrow passages, gardens, parking and public areas because they affect access and protection. Shared buildings may need a factor or co-owner contact; occupied rooms can affect preparation.
Use the assessment to define material and repair boundaries
Identify the tile and slope, map defects, record junction and underlay evidence, and state what is concealed. Set out local or wider repair, matching assumptions, access to assess, and connected ridge, valley, lead or chimney work. Treat unknown substrate as a limitation.
Use general repairs for mixed defects and inspection where cause remains unclear. Check the heritage route before changing protected fabric. Share spare-tile details, leak history and assessment purpose so suitability and current availability can be confirmed.
