The short answer
Start with the places water collects: valleys, the join between roof and chimney, the eaves and the verges. Then look for slipped or cracked coverings from the ground, and in the loft for daylight, stains and damp timber. Photographs taken on a survey confirm what you can and cannot see yourself.
A village with Pewsey's history has roofs of every generation standing side by side. The streets near the church, the lanes running down towards the canal and the later roads on the outskirts each carry a different mix of ages, and the faults follow the age of the house.
Q1.1Why check the junctions first?
Water gets in at junctions far more often than across open slopes. The valley where two roofs meet, the flashing where a slope meets a wall and the lead around a chimney stack are where we begin. A flashing is lead or another metal worked into the join where the covering meets anything rising through it, so rain runs over the join instead of into it. Once the lead has cracked or lifted, water runs behind it, and the damp patch can show on a ceiling a good way from the real fault, which is why guessing from indoors so often goes wrong.
Q1.2What shows on the covering itself?
On a tiled or slated slope, slipped, cracked or missing pieces are usually visible from the ground with binoculars. Old nails fail, tiles lose their nibs, and moss holds water against the surface for weeks. Our roof inspections and surveys page explains what a visit photographs and what the written quote contains afterwards.
Q1.3What can you see from the loft?
Daylight showing through, dark staining on rafters and battens, and a musty smell each tell you something. So do wet patches around the chimney breast. If the loft can be reached safely, a torch and a phone camera give us a useful starting point before we arrive, though nobody should climb onto the roof itself.
Our habit is to price the narrowest job that cures the leak, so a handful of refixed tiles and a new flashing is a perfectly good result when that is all the photographs show.