NHBC Standards 2006

2.3 Timber preservation (natural solid timber)


2.3 - S1Sitework standards
2.3 - S2Protection and storage
2.3 - S3Treatment of cut surfaces

2.3 - S1
All sitework shall:
(a) comply with the Technical Requirements
(b) take account of the design
(c) follow established good practice and workmanship

Sitework that complies with the design and the guidance below will be acceptable for timber preservation.

Timber treated with copper containing preservations should be re-dried to a moisture content of 20% for at least 7 days before being in contact with metal fittings.

In situations where occasional dampness is expected, metal fittings in contact with timber treated with copper containing preservatives should be galvanized. Where timber treated with copper containing preservatives is likely to become wet, fittings of austenitic stainless steel should be used.

Check that when delivered to site, timber and joinery products have received the specified treatment. This should be stated on the delivery note.


2.3 - S2
Timber and joinery shall be stored and protected to ensure it is in a suitable condition when installed in the dwelling

It is important when timber and joinery products are stored that they are:

  • protected from damage immediately upon delivery
  • protected from the weather
  • stored off the ground
  • stored in a way which limits the risk of distortion
  • stored so that air can circulate freely around them.


2.3 - S3
Timber which has been preservative treated and cut shall be re-treated on the cut surfaces

Timber should not be cut after treatment but where this is unavoidable (either at the treatment plant or on site) all cut surfaces should be given two liberal applications of a suitable colour tinted preservative. The purpose of the colour tinting is to enable checks to be made that re-treatment has been carried out.

Only in situations where colour tinting will affect the appearance of the timber when fixed to the dwelling will clear preservatives be acceptable for this purpose.

The site applied preservative should be compatible with the original treatment.