Publishing and copyright information

The BSI copyright notice displayed in this document indicates when the document was last issued.

The following BSI references relate to the work on this document:
Committee reference B/543
Draft for comment 14/30277336 DC

Publication history

First published December 2014

Foreword

Publishing information

This part of BS 8605 is published by BSI Standards Limited, under licence from The British Standards Institution, and came into effect on 31 December 2014. It was prepared by Panel B/543/-/2, External timber cladding, under the authority of Technical Committee B/543, Round and sawn timber. A list of organizations represented on this committee can be obtained on request to its secretary.

Relationship with other publications

BS 8605 is published in two parts:

Part 1: Method of specifying; and
Part 2: Code of practice for design and installation.

Some types of external timber cladding are covered by harmonized European Standards BS EN 14915 or BS EN 13986. This British Standard offers suppliers and designers additional information relevant to the UK’s climate and construction practices.

Use of this document

It has been assumed in the preparation of this part of BS 8605 that the execution of its provisions will be entrusted to appropriately qualified and experienced people, for whose use it has been produced.

Presentational conventions

The provisions of this standard are presented in roman (i.e. upright) type. Its requirements are expressed in sentences in which the principal auxiliary verb is “shall”.

Commentary, explanation and general informative material is presented in smaller italic type, and does not constitute a normative element.

Contractual and legal considerations

This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

Introduction

External timber cladding assemblies can comprise several types of timber or wood-based components and can be used in a variety of ways. This complexity can cause difficulties when specifying because:

suppliers need to know what performance characteristics are important and which of these should be declared in product documentation;
designers need to know what performance characteristics need to be taken into account and which should form part of a cladding specification.

Several factors need to be considered when determining which performance characteristics should be specified. These vary depending upon the type of timber cladding: boards, for example, involve different considerations from shingles. There is, however, no single source of information that suppliers and designers can use when preparing product documentation or specifications.

External timber cladding made of boards or wood-based panels is within the scope of harmonized standards BS EN 14915 and BS EN 13986, respectively. This means that where a characteristic is covered by one of these standards, manufacturers need to document their products in accordance with that standard. Some provisions only apply in specific circumstances. There is no harmonized standard for shingles and shakes.
Neither harmonized standard covers all of the performance requirements that apply to external timber cladding. Some additional requirements are given in product standards BS EN 14519, BS EN 14951 and BS EN 15146, although not all criteria are covered.

Accordingly, this standard complements the harmonized standards and product standards for external timber cladding by:

listing the main performance requirements that might be applicable to external timber cladding in the UK;
specifying requirements for areas that are outside the scope of harmonized standards; and
giving guidance on requirements that are covered by BS EN 14915 or BS EN 13986.

As a method of specifying, this part of BS 8605 gives verifiable performance characteristics, which can be controlled by product manufacturers and distributors. Issues, such as cavity ventilation, that become applicable during design and installation are addressed in BS 8605‑2.

1 Scope

This part of BS 8605 describes methods of specifying the characteristics of external timber cladding products from which selection has to be made and for which values might have to be agreed between the purchaser and manufacturer.

This part of BS 8605 complements harmonized standards BS EN 14915 and BS EN 13986. It lists all performance requirements that might apply to external timber cladding in the UK and provides a method of specifying those requirements that are outside the scope of those standards, but which are relevant to the UK’s climate and construction practices.

This part of BS 8605 specifies characteristics of components at the time they are transferred to the purchaser. It is intended for use by specifiers of external timber cladding components.

NOTE 1 Suppliers can refer to this British Standard for guidance when manufacturing external timber cladding components and preparing technical documentation.

This part of BS 8605 applies to external timber cladding designed to function as a rainscreen. The types of external timber cladding components covered by this standard are boards, shingles and shakes, and wood-based panels. Requirements are listed separately for each of these product types.

NOTE 2 BS 8605‑2 gives guidance for designers of external timber cladding assemblies and installers of such products on site. It also gives guidance on the selection of other components in the external timber cladding assembly. These include, for example, cavity barriers, breather membranes, fasteners and flashings.

This part of BS 8605 does not apply to components to be used as non-rainsceen cladding, roofing, solar shading, pressure equalized cladding, double skin facades, curtain walling or any kind of wall covering intended solely for interior use. Nor does it apply to cladding made of composite materials such as fibre cement board or wood-plastic composites.

2 Normative references

3 Terms and definitions

4 General

5 Moisture content

5.1 General

5.2 Moisture content of boards

5.3 Moisture content of shingles and shakes

5.4 Moisture content of wood-based panels

5.5 Moisture content measurement

6 Durability against biological attack

6.1 Natural durability

6.2 Wood modification

6.3 Preservative treatment

7 Species

7.1 Species for boards, shingles and shakes

7.2 Species for wood-based panels

8 Grade

8.1 General

8.2 Grades for boards

8.3 Grades for shingles and shakes

8.4 Grades for wood-based panels

9 Geometrical characteristics

9.1 General

9.2 Geometrical characteristics of boards

9.3 Geometrical characteristics of shingles and shakes

9.4 Geometrical characteristics for wood-based panels

10 Warp

10.1 Warp in boards

10.2 Warp in shingles and shakes

10.3 Warp in wood-based panels

11 Resistance to fixing

11.1 Resistance to fixing of boards

11.2 Resistance to fixing of shingles and shakes

11.3 Resistance to fixing of wood-based panels

12 Dimensional stability

12.1 Dimensional stability of boards

12.2 Dimensional stability of wood-based panels

13 Reaction to fire

13.1 Reaction to fire classification of boards

13.2 Reaction to fire classification of shingles and shakes

13.3 Reaction to fire classification of wood-based panels

14 Resistance to deformation

15 Bonding quality

15.1 Bonding quality for boards

15.2 Bonding quality for wood-based panels

16 Coating systems

16.1 Coating systems for boards

16.2 Coating systems for wood-based panels

17 Wood density

18 Hygrothermal performance

19 Release of dangerous substances

20 Moisture resistance

21 Airborne sound insulation

Bibliography

BS 8605-1:2014

External timber cladding - Method of specifying

Current, Under Review

Published:

31 Dec 2014