Sooner or later every viewing reaches the question of age: how old is the boiler, how long will the roof last, when were the windows fitted? Lifespan tables promise a quick answer, and they are useful — once you know what each figure is, where it comes from and what it cannot say about the house in front of you.
Building components have no fixed life expectancy. Tables disagree because they measure different things: a German federal table assumes 18 years for a wall-hung gas condensing boiler, a US study reports 21 years for a gas boiler, and both put tiled or slate roofs at 50 years or more. Condition decides.
Three sources, three kinds of figure
The figures here come from three kinds of source. A German federal table sets assumed service lives for life-cycle calculations, a 2007 US study asked manufacturers and trade associations, and a French product declaration for uPVC windows uses a default reference life. All three are legitimate, and none of them is a measurement of the house you are viewing.
The BBSR table (Germany). The Federal Institute for Research on Building, Urban Affairs and Spatial Development (BBSR) publishes service lives of building components for life-cycle cost and life-cycle assessment calculations: the assumed period after which a component installed today will probably be replaced. The current file dates from 13 March 2026, with values as of 4 November 2025. The figures refer to a 50-year assessment period, so “50 or more” means no replacement within that period — a cap, not a measured maximum. According to the BBSR, the values draw on literature and expert experience, include renewals made for legal or aesthetic reasons, and rest partly on experience rather than measurable tests; binding statements such as guarantees, construction contracts or expert reports cannot be derived from them.
The NAHB study (United States). In the summer of 2006, the National Association of Home Builders surveyed manufacturers, trade associations and researchers by telephone; the study was published with Bank of America Home Equity in February 2007. Many of the people interviewed stressed that maintenance greatly affects life expectancy, and that products are often replaced long before — or after — the end of their practical life. The report itself warns readers not to make buying decisions based solely on its figures. Its values reflect US products and climates.
Product declarations (France). Environmental product declarations state a reference service life for a product. For uPVC windows, the collective declaration of UFME, the French joinery manufacturers’ association, gives 30 years — a default value taken from the French supplement to the European standard EN 15804, not the result of a durability test.
For roof coverings, two further sources show the upper end: conservation guidance on historic roofs from the US National Park Service (1993), and ageing tests on roof tiles reported by the UK Building Research Establishment (BRE, 2014).
The table: one component, several figures
The table sets published figures for the components that dominate a repair budget side by side. BBSR values are as of November 2025; for building-fabric rows, the 2017 edition is in brackets where it gave a different value for the same component. NAHB figures date from 2007. A dash means the source gives no comparable value.
| Component | BBSR, Germany (years) | NAHB, United States (years) | Other published figure |
|---|---|---|---|
| Clay roof tiles | 50 or more | clay or concrete: “lifetime” | about 100 years for historic clay tile roofs (US National Park Service, 1993) |
| Concrete roof tiles | 50 or more | clay or concrete: “lifetime” | 60 years suggested by manufacturers for clay and concrete tiles; tests on two roofs with tiles around 60 years old led BRE to conclude they could last several decades more (BRE, 2014) |
| Natural slate | 50 or more | 50+ | 60 to 125 years or longer, depending on the slate (US National Park Service, 1993) |
| Flat-roof membrane, bitumen | 30 on unused roofs where falls and layers meet the design standard; 35 below insulation; 15 for membranes outside the listed cases | modified bitumen 20; coal and tar 30 | — |
| Flat-roof membrane, plastic or elastomer | 30 on unused roofs where thickness and falls meet the design standard; 40 below insulation | — | — |
| Gutters and downpipes | plastic 25 (20); galvanised steel 35 (30); stainless steel, copper, zinc or uncoated aluminium 50 or more | aluminium 20; galvanised steel 20; copper over 50 | — |
| Windows, uPVC frames | 50 or more (40) | — | 30, default reference life (UFME product declaration) |
| Windows, treated softwood | 50 or more (40) | wood windows: upwards of 30 | — |
| Gas condensing boiler, wall-hung | 18 | gas boilers, type not stated: 21 (first-owner use) | — |
| Heat pump, air-to-water | 18 | heat pumps, type not stated: 16 | — |
| Electrical installation | 30 | copper wiring: “lifetime” | — |
| Heating pipes | steel 50 or more; copper 40; plastic 30 | — | — |
| Render on masonry | mineral 50 or more (45); silicate, silicone or synthetic resin 45 (30) | stucco 50–100 | — |
| Render on external insulation | 45 (30) | — | — |
| External insulation system with a national technical approval | 50 or more (40) | — | — |
Sources: BBSR table of service lives (file of 13 March 2026, values as of 4 November 2025; edition of 24 February 2017), NAHB study (February 2007), UFME product declaration for uPVC windows, US National Park Service Preservation Briefs 29 and 30 (1993), BRE (2014). Retrieved in September 2026.
Where the sources agree, it is mostly on short-lived building services. For long-lived parts they rarely even state an upper value — which is why a table cannot tell you how long a particular roof or window has left.
Why the numbers disagree
Lifespan tables disagree because the same word covers different things. The BBSR sets assumptions for 50-year life-cycle calculations and caps long-lived parts at “50 or more”. The NAHB recorded what manufacturers and trade associations said. The French window declaration uses a default reference life. Maintenance, climate, workmanship and changing tastes then move the real figure for each house.
- Definitions. An assumption for a life-cycle calculation, a manufacturer’s estimate and a default value in a product declaration are three different things that happen to share a unit. Most charts of the life expectancy of building materials do not say which of the three they show.
- Caps. “50 or more” and “lifetime” hide the difference between a tile that lasts 60 years and one that lasts 120. For long-lived parts, the tables rarely state an upper value at all.
- Replacement for other reasons. The BBSR includes renewals made for legal and aesthetic reasons. The NAHB interviewees noted that products are often replaced before the end of their practical life — or kept long after it.
- Maintenance. Both the NAHB interviewees and the conservation guidance on roofs name maintenance as a deciding factor. A serviced boiler and a neglected one of the same age are not the same boiler.
- Climate and products. US figures describe US products in US climates. A figure from one market says little about the same component elsewhere.
- System and component. A roof covering usually outlasts the nails, battens and flashings that keep it in place, which is why the age of a roof is really several questions.
The same authority, two editions
Lifespan figures also change between editions of the same table. Between the BBSR’s 2017 edition and its values as of 2025, uPVC windows and external insulation systems rose from 40 to 50 years or more, render on insulation from 30 to 45, galvanised steel gutters from 30 to 35 and plastic gutters from 20 to 25.
The houses did not change between the two editions; the table’s assumptions and definitions did. A lifespan figure is a convention with a publication date.
The revision also regrouped flat-roof membranes: exposed membranes on roofs built to the design standard now have 30 years, membranes below insulation 35 to 40, and membranes outside the listed cases 15. For a buyer, the lesson is practical. A table value carries a publication date, and a statement that something is “at the end of its life” is only as current as the figure behind it.
What to check instead of counting years
A few observations and documents say more than a component’s age: the service record of a boiler or heat pump, a recent inspection of the electrics, the seals and timber of windows, and the details rather than the tiles of a roof. Without them, the age figure is all you have — treat it as a question.
| Component | What says more than the year |
|---|---|
| Pitched roof, tiles or slate | slipped or broken pieces, flashings at chimneys, ridge bedding, stains in the loft |
| Flat roof | blisters, crazing, standing water, open seams, split flashings |
| Gutters and downpipes | leaking joints, overflow marks on the wall, rust |
| Windows | condensation between the panes, worn seals, soft timber at sills and bottom rails, stiff hardware |
| Boiler or heat pump | a service record with dates, recurring faults, spare parts still obtainable |
| Electrical installation | a recent inspection report, the age and type of the distribution board, signs of do-it-yourself alterations |
| Heating pipes | corrosion at joints, damp patches below pipe runs, a system that needs frequent topping up |
| Render and external insulation | cracks along board joints, hollow-sounding areas, algae, damage at the base |
Damp patterns on walls, which often start at gutters and render, are covered in damp when buying a house.
How briven uses component age
briven is built to estimate the age of building elements from visible evidence — aerial imagery, photos, documents — where it allows, instead of assuming every part is as old as the building. It is designed to weigh that age against the condition the evidence shows, state a confidence level for each element and list what to check on site.
A typical service life is one input to that assessment, weighed with the condition the evidence shows — never a forecast of how long an element has left. briven is preparing its launch; you can join the waiting list on the English home page.
Frequently asked questions
There is no single figure, only conventions. The German federal BBSR table, with values as of November 2025, assumes 18 years for a wall-hung gas condensing boiler, 30 years for electrical installations and 50 years or more for clay tiles or slate. How a particular component ages depends on its condition and maintenance.
Published figures put a gas boiler at around two decades: 18 years for a wall-hung gas condensing boiler in the BBSR table (values as of November 2025) and 21 years for a gas boiler in the 2007 study by the US National Association of Home Builders. The service record says more about one particular boiler.
Roof coverings of clay, concrete or slate are among the longest-lived parts of a house: the BBSR table lists all three at 50 years or more, the top of its scale, meaning no replacement within its 50-year assessment period. The fixings, flashings and underlay usually fail first, so a roof can need work long before its tiles or slates do.
Because they measure different things. The BBSR table sets assumptions for life-cycle calculations over a 50-year period, the NAHB study asked manufacturers and trade associations, and a French product declaration for uPVC windows uses a default reference value. The same word covers several definitions, and none of them is a forecast for one house.
No. The BBSR states that its values rest partly on experience rather than on measurable tests, and that no binding statements such as guarantees, construction contracts or expert reports can be derived from them. A component past its table value can work well for years.
Sources and standards(6)
- BBSR — Service lives of building components (Nutzungsdauern von Bauteilen, BNB)German Federal Institute for Research on Building, Urban Affairs and Spatial Development. File of 13 March 2026 with values as of 4 November 2025, and the edition of 24 February 2017. Also the definition of the values and the statement that no binding conclusions can be drawn from them. In German.
- NAHB / Bank of America Home Equity — Study of Life Expectancy of Home Components (February 2007)Copy of the original report hosted by a third party. Telephone survey of manufacturers, trade associations and researchers in summer 2006. Source of the US figures, including the warning not to base buying decisions solely on them.
- UFME (Union des fabricants de menuiseries) — FDES « Fenêtres et portes-fenêtres PVC, teintes claires (L> 0,82), avec vitrage d’épaisseur de verre cumulée inférieure à 12 mm », Mars 2023Collective environmental product declaration of the French joinery manufacturers’ association. Reference service life of 30 years, taken from table H2 of the French supplement to EN 15804. In French.
- US National Park Service — Preservation Brief 29: The Repair, Replacement, and Maintenance of Historic Slate Roofs (Jeffrey S. Levine, 1993)Service life of slate roofs of 60 to 125 years or longer, depending on the slate, the roof and its location.
- US National Park Service — Preservation Brief 30: The Preservation and Repair of Historic Clay Tile Roofs (Anne E. Grimmer and Paul K. Williams, 1993)Clay tile among the longest-lived historic roofing materials, generally about 100 years.
- BRE — Using BRE standards to test the longevity of ageing roof tiles (12 February 2014)Manufacturers’ suggested service life of 60 years for clay and concrete tiles, and BRE’s assessment that tested tiles of that age could last several decades more.