Check a site
Enter a UK postcode to check whether the site falls within the geographical area in which softwood roof timber must be treated against House Longhorn Beetle under Approved Document A, Section 2B.
Designated Area — Full Coverage
Designated Area — Parish / Sub-district Only
About this requirement
Why treatment is required. House Longhorn Beetle (Hylotrupes bajulus ) lays its eggs in cracks in untreated softwood. The larvae feed on the wood for 3–10 years before emerging as adults, long enough to cause serious structural damage to roof members before an infestation is detected externally.
Why the area is where it is. The designated area in AD A § 2B2 was mapped from BRE field surveys in the 1950s–1970s, which found persistent infestations concentrated in north-west Surrey and adjoining parts of Berkshire and Hampshire. The boundary list has barely changed since BRE IP 8/94.
Current risk picture. Modern kiln-dried structural softwood (C16/C24 graded at ~18–20% moisture content) is a poor host — HLB larvae need damper, slower-seasoned timber to establish. Active infestations in new-build properties are now rare even inside the designated area, but the statutory requirement remains in force and must be complied with.
Regulatory status. Approved Document A is currently under HSE review (call for evidence published 2023). The HLB area and treatment clause are among the items under consideration. Always confirm with the current AD and any published amendments before specifying.
Source, caveats & methodology
Area list taken from Approved Document A: Structure (2013 edition, incorporating 2013 amendments), Section 2B2 — Areas in which the House Longhorn Beetle is a problem. Boundary polygons drawn from OpenStreetMap administrative data via Nominatim, accurate to roughly 3 m.
Basemaps: Esri World Imagery (satellite) and CARTO Positron (map). Postcode geocoding: postcodes.io (ONS-backed). District classification drives the yes/no/check result; parish names and postcode sectors resolve sub-district cases.
Not a substitute for professional judgement. The tool indicates probable coverage; the final specification decision rests with the designer and local Building Control. Always confirm against the current edition of the AD before specifying.
Data current as of 23 April 2026. · Prepared by Knight Designs Ltd, Timber Frame Consultants.
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