How long does a felt roof last?

Why there is no single felt-roof age

The visible mineral surface is only the top layer of a complete roof. Its performance depends on the underlayers, the deck, the way water falls to the outlet, and the detailing at walls and edges. A simple garage roof with an open outlet has fewer difficult junctions than a dormer with several upstands and penetrations. Exposure and access matter too. That is why the published service range gives 15–25 years for modern three-layer torch-on felt rather than pretending every roof reaches the same birthday. Condition and construction are stronger evidence than an installation date on its own.

Modern torch-on felt and older coverings

HRD’s stated felt specification uses an SBS-modified, three-layer torch-on system rather than treating all bituminous coverings alike. The layers and prepared deck create the waterproof build-up; the mineral-finished cap protects the surface. Older pour-and-roll material and lightweight coverings can age differently and may hide previous patches. If you do not know what is installed, look at the edge detail or paperwork rather than guessing from colour. A survey can identify whether the roof is a complete bonded system, an overlay or a collection of repairs, which changes how sensible another local patch would be.

The deck often decides the answer

Felt can only perform as well as the boards beneath it. Soft areas, repeated dips or local movement suggest the deck needs attention even if the cap sheet has no obvious split. Conversely, a small surface defect over a firm, dry deck may remain a repair rather than a replacement. The site’s flat-roof process strips the old covering where necessary, checks the deck and falls, replaces unsound boarding and then applies the selected system. That sequence matters because laying a fresh waterproof layer over wet or moving boards preserves the cause of the problem instead of removing it.

Drainage and ponding shorten useful life

A flat roof still needs a fall. Water should travel towards an outlet or drip rather than sitting in broad depressions. Debris around the outlet can create temporary ponding; a poor fall or sagging deck creates a recurring one. Clear leaves and moss first, then observe what remains after the rest of the surface has drained. Blistering, green growth across a wet zone and staining at an edge can all point to retained water. A patch on the cap sheet will not alter the fall, so drainage and covering need to be assessed together before money is spent.

Upstands, trims and junctions deserve close attention

Many leaks begin where the flat roof meets something else: a wall, rooflight, vent, soil pipe, edge trim or pitched covering. These details accommodate movement and direct water away from vulnerable edges. If an upstand is too low, a trim has moved or a junction has been repeatedly covered with mastic, the open field of felt may not be the fault at all. Trace the route of water rather than assuming the largest visible surface needs replacing. HRD’s written flat-roof specification includes upstands, outlets and trims because those details are part of the roof, not optional finishing pieces.

Signs a repair may still be sensible

A local puncture, one failed edge or a clearly defined split can be repairable where the surrounding felt is stable and the deck is sound. The repair needs to tie into compatible, well-adhered material and address why the damage happened. A branch impact is different from movement across the whole deck; one disturbed trim is different from widespread blistering. Ask for the condition of the surrounding system to be recorded, not merely a price to cover the visible mark. A useful repair buys dependable service, whereas a cosmetic patch only changes how the defect looks.

Signs replacement should be considered

Widespread blistering, repeated leaks in different places, a soft or uneven deck, failed junctions throughout and extensive previous patching all shift the balance towards replacement. So does a roof whose insulation or build-up needs changing while the covering is already being stripped. Replacement is not automatically required because a roof is old, but age combined with several connected failures is meaningful. The site’s repair-or-replace guidance recommends comparing the likely cycle of further access and patching with one planned renewal, then setting out both choices rather than using a leak as a sales shortcut.

How to get a useful assessment

Provide photographs of the whole roof, its outlets, wall junctions and any marks inside. Note whether staining follows every rainfall, wind-driven rain or only prolonged wet weather. During a visit, the deck, falls, edges, penetrations and insulation build-up should be considered alongside the felt. Ask the quote to separate removal, boarding, insulation, membrane layers, trims, access and waste. That makes different proposals comparable and shows whether somebody is pricing a complete roof or only a new visible surface. HRD offers site inspections within its stated 15-mile radius of Hampton before a fixed specification is agreed.

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