Fact-check claims about wood

Untreated Norway spruce cladding in a Nordic coastal climate lasts as long as untreated European oak in the same exposure.

Not verified

Modelled service-life estimates in the Wood Intelligence Index (WI-SL v1.2.0, calibrated with WI-CAL v1.0.0) place untreated Norway spruce in use class 3.1 well below European oak heartwood in the same exposure. EN 350 classifies spruce heartwood as slightly to non-durable (DC 4-5) and oak heartwood as durable (DC 2). The two are not equivalent in the same detail and exposure.

Detailing that keeps end grain off horizontal surfaces has a larger effect on the service life of exterior wood than the choice of species alone.

Partially verified

Moisture-trapping details are consistently identified as a dominant driver of decay onset in exterior wood, and the Wood Intelligence decay model gives detailing and exposure factors a weight comparable to, and in wet use classes larger than, the species durability factor. The claim holds for use class 3.2 details in the modelled cases, but it is not universally true across all climates and species combinations, so it is verified only in part.

Wood Intelligence service-life figures are measured field results.

Not verified

All service-life figures published on this platform are modelled estimates produced by method WI-SL v1.2.0 and reported with P10/P50/P90 uncertainty bands. They are compared against a validation set of 24 documented field cases (WI-VAL v1.0.0), but the published figures themselves are model outputs, not direct field measurements.

Decay risk for exterior timber is essentially the same across Europe because modern buildings are detailed similarly.

Incorrect: climate-driven decay dose varies by a large factor across European climate zones.

Using ERA5 reanalysis temperature and relative-humidity data as input to the dose-response model in Method WI-SL, the annual decay dose differs several-fold between a dry continental inland zone and a humid Atlantic coastal zone. Detailing modifies exposure but does not remove the underlying climatic gradient. Zone-level results and their P10/P50/P90 ranges are published in the Wood Intelligence Index.

Thermally modified timber is classified as durability class 1 under EN 350.

Incorrect as stated: EN 350 durability classes describe natural durability of wood species, not modified products.

EN 350:2016 assigns natural durability classes to species of wood. Modified timber products are assessed with other routes, typically EN 113 or field testing under EN 252, and results vary by process and intensity. Reported performance for modified timber can be high, but citing an EN 350 durability class for a modified product is a category error.

Untreated softwood cladding in a temperate Northern European climate lasts 30 years or more without maintenance.

Partly correct: service life depends strongly on use class, detailing and orientation, not on species alone.

Modelled service life for untreated Norway spruce cladding in a vertical, well-drained use class 3.1 situation falls in the range of roughly 20-35 years (P10-P90) in a Nordic coastal climate, but drops materially for horizontal, shaded or splash-exposed details in use class 3.2. A single figure of "30 years or more" cannot be applied to all untreated softwood cladding. Values are modelled estimates from Method WI-SL, not measured observations.