Publishing and copyright information

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

© The British Standards Institution 2017

Published by BSI Standards Limited 2017

ISBN 978 0 580 98171 5

ICS 79.040

The following BSI references relate to the work on this document:
Committee reference B/518
Draft for comment 06/30148363 DC; 11/30238044 DC; 17/30359032 DC

Foreword

Publishing information

This British Standard was published by BSI and came into effect on 31 May 2007. It was prepared by Technical Committee B/518, Structural timber. A list of organizations represented on this committee can be obtained on request to its secretary.

Supersession

BS 5756:2007+A1:2011 superseded BS 5756:1997, which has been withdrawn.

BS 5756:2007+A2:2017 supersedes BS 5756:2007+A1:2011, which was partially superseded by BS EN 16737: 2016.

Information about this document

The start and finish of text introduced or altered by Amendments No 1 and 2 is indicated in the text by tags and . Minor editorial changes are not tagged.

This British Standard conforms to the requirements of BS EN 14081‑1.

This British Standard specifies the means of assessing visually the quality of temperate hardwood for which characteristic values as strength classes are given in BS EN 338. Assignments of species/grade combinations to those strength classes are given in BS EN 1912, which incorporates the grades defined in this standard for which design values are given in BS 5268‑21⁾ and BS EN 1995‑1‑1. Additional assignments for grades of UK oak and sweet chestnut are given in PD 66932⁾. A European Standard has been published that provides rules for the structural grading of tropical hardwood timber. Tropical timber is therefore no longer within the scope of this standard.

This British Standard specifies two visual strength grades (General Structural Temperate Hardwood, TH1 and TH2) for timber with a thickness less than 100 mm or cross-sectional area less than 20 000 mm², and two visual strength grades (Heavy Structural Temperate Hardwood, THA and THB) for timber with a thickness and cross-sectional area equal to or greater than these values.

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.

1 Scope

This British Standard specifies a method of strength grading temperate hardwood visually for structural use.

The permissible limits of characteristics for temperate hardwoods are specified for two visual strength grades for large size timber, designated “Heavy Structural Temperate Hardwood” (THA and THB), and two visual strength grades for smaller size timber, designated “General Structural Temperate Hardwood” (TH1 and TH2).

This British Standard applies to temperate hardwoods, graded for use in the United Kingdom.

2 Normative references

3 Terms and definitions

4 Strength graded timber

4.1 Supervision of strength grading operations

4.2 Sizes

4.3 Processing of visually graded timber

4.4 Resawing or surfacing

4.5 Cross-cutting

4.6 Moisture content

4.7 Acceptance limits for visually graded timber

4.8 Abnormal defects

5 Grade requirements

5.1 Text deleted

5.2 Requirements for the structural temperate hardwood grades (TH1, TH2 and THA, THB)

5.3 Abnormal defects

6 Text deleted

7 Measurement of characteristics

7.1 Knots

7.2 Slope of grain

7.3 Wane

7.4 Fissures

7.5 Text deleted

7.6 Distortion

8 Marking4⁾

8.1 General

8.2 Information to be marked on the product

8.3 Information to be marked on the product or in accompanying documentation

BS 5756:2007+A2:2017

Visual strength grading of temperate hardwood. Specification

Current

Published:

30 Nov 2017