Building standards are currently under review following the Grenfell Tower fire. Although this was not a timber building and did not have timber cladding, the use of combustible construction materials is coming under increased scrutiny.

Amendments to Approved Document B, Fire safety, have now been published for use in England.

The amended Regulation 7(2) states that ‘building work shall be carried out so that materials which become part of an external wall, or specified attachment, of a relevant building are of European Classification A2-s1 d0, or Class A1 (non-combustible)… where a ‘relevant building’ means a building with a storey (not including roof-top plant areas or any storey consisting exclusively of plant rooms) at least 18m above ground level and which:

  1. Contains one or more dwellings
  2. Contains an institution
  3. Contains a room for residential purposes (excluding any room in a hotel or boarding house).

This requirement does not apply to doors, door frames or window frames.

The government interprets relevant buildings as including (where there is a storey at least 18 metres above ground level): ‘Residential flats/rooms (excluding any room in a hotel, hostel or boarding house), hospitals, care homes, sheltered housing, dormitories in boarding schools, student accommodation and schools which are built as part of the government’s centrally delivered build programmes’

You can download the document here.

In cases other than relevant buildings (see above), the advice for external cladding – for our purposes, timber cladding, is essentially as follows (see page 7):

For any building other than a recreation or assembly building of 18m in height or lower:

  • No provision
  • Unless any wall is less than 1000 mm from a boundary,  when the cladding must be FR treated as a minimum to Euroclass B-s3, d2

For any building other than a recreation or assembly building over 18m in height:

  • Cladding for the lower 18m of the building must be FR treated as a minimum to Euroclass C-s3, d2
  • Cladding above 18m must be FR treated as a minimum to Euroclass B-s3, d2
  • Unless any wall is less than 1000 mm from a boundary,  when the cladding of the entire wall must be FR treated as a minimum to Euroclass B-s3, d2

For an assembly or recreation building of more than one storey:

  • Cladding up to 10 m above the ground, or 10 m above any part of the building to which the public have access must be FR treated as a minimum to Euroclass C-s3, d2
  • Unless any wall is less than 1000 mm from a boundary,  when the cladding of the entire wall must be FR treated as a minimum to Euroclass B-s3, d2

Untreated timber cladding meets Euroclass D. Timber cladding treated to Euroclass B and C is widely available from specialist timber merchants.

Interior Cladding

Broadly speaking, interior cladding should be treated to Euroclass C-s3, d2. See full guidance in Approved Document B for details.