How can you tell how old a roof is?

1Reading the covering from the street

Start with what the roof is made of, because each material has a typical working life. Natural slate that was laid well is quoted at 80 to 100 years or more. For clay tiles Marley refers to a minimum expected life of 60 years, determined by the Building Research Establishment, and cost guides give concrete tiles as often 30 to 60 years. They are ranges, not promises.

Appearance helps too. Hand-made clay peg tiles with a slight camber and uneven colour belong to older roofs, while crisp, uniform interlocking concrete tiles suggest something later. Thick lichen, softened slate edges and rust at nail heads all record years of weather. Be cautious with historic roofs, though. The 60-year clay figure is described by one conservation source as unreliable for old peg-tile roofs, and a roof tended carefully can run on well beyond the number.

From the pavement, binoculars are enough. Do not go up a ladder to look.

2What the loft shows under the tiles

Often the roof space gives away more than the outside does. Take a torch and look at what sits beneath the covering. An older roof may have bitumen felt that has turned brittle and torn, or sometimes no underlay at all, with daylight or draughts at the laps. A newer roof tends to have a plastic-based breathable membrane that is smooth and whole.

Check the battens too. These are the thin timber laths that carry the tiles. Dark, dry, split battens suggest age and past leaks, while clean squared timber with bright nail heads points to recent work. Some membranes and tile backs carry a maker's stamp or batch mark, which occasionally gives a date. Not every roof has one, and a missing stamp tells you nothing either way.

Stay on the boards or the hatch edge. Never step between ceiling joists, and never climb onto the roof to take a closer look. Our survey photographs cover this ground safely.

3Ridge and edge fixings as dating clues

How the ridge is held in place is a handy marker. Since the 2014 revision of BS 5534, ridge and hip tiles now get a clip or screw as well, leaving the mortar as bedding rather than the sole restraint. A ridge bedded in mortar alone, cracked and crumbling, therefore probably predates that change or was done without regard to it. A dry-fix ridge running on clips and a tested system, which BS 8612:2018 covers, points the other way.

The roof edges tell a similar story. Gable-end verges relying on mortar pointing alone, and lead or cement flashings at walls that have lifted or split, show that the weatherproofing details have worn even where the tiles themselves still look sound. Moss can hide the damage, which makes it hard to judge from the garden. We note these on the survey with photographs, because they weigh heavily in the choice between mending and renewing, and they sit behind a good many leaks that people blame on the tiles.

4Records, certificates and what neighbours know

Paper can answer the question faster than any inspection. Look through the deeds pack or the sale file for invoices, guarantee papers and old survey reports. If a previous owner re-roofed, the work may have needed Building Regulations approval, and a completion certificate would date it. You can ask the building control team at Adur and Worthing Councils whether a record exists for your address.

On an estate from one period, neighbours often know when their roofs were done. A row of homes built together tends to age together, though some will have been renewed earlier. Landlords and managing agents may hold maintenance logs as well, and a previous owner may still remember who did the work. Where no document survives, the signs on the covering and in the loft give a sensible estimate. Write down what you find, with dates for anything you can confirm, and keep the notes with the house papers for whoever owns it next. The estimate we give you, and we describe it as an estimate in the survey rather than a fact.

5Why age and condition are different things

A forty-year-old concrete tile roof that has been kept clear, re-ridged and re-flashed can be in better shape than a fifteen-year-old roof laid badly. Age gives a rough sense of the life stage; condition tells you what to do next. Two roofs of the same age on the same street can need completely different work, because exposure, pitch, workmanship and upkeep differ. A survey, with pictures taken across your own slopes, separates the two. Sometimes the sensible advice for a roof that looks old is a modest repair, not a new covering.

If the age you arrive at is advanced, read why a new covering cannot just go over the old one, and then what to expect during a re-roof. If you are about to sell, whether a new roof adds value is worth a read. For the wider picture, from the first survey through to clearing the site, see our roof replacement page.