SIST EN 336:2013

Structural timber - Sizes, permitted deviations

This European Standard specifies two classes of permitted deviations from target sizes for structural timber of softwood and hardwood species.
It also specifies the moisture content to be used as a reference point for the measurement of sizes, and gives average values for changes in size due to changes in moisture content.
It is applicable to sawn and prepared square-edged structural timber with parallel edges having sawn thicknesses or widths greater than 6 mm.

Bauholz für tragende Zwecke - Maße, zulässige Abweichungen

Diese Norm legt zwei Klassen zulässiger Abweichungen von den Sollmaßen für Bauholz für tragende Zwecke aus Nadel  und Laubhölzern fest.
Die Norm legt auch die Holzfeuchte fest, die als Bezugspunkt für die Ermittlung der Maße dient, und es werden Mittelwerte für die Maßänderungen bei Änderungen der Holzfeuchte angegeben.
Sie gilt für Bauschnittholz für tragende Zwecke mit Rechteckquerschnitt und parallelen Kanten mit Dicken oder Breiten von mehr als 6 mm.

Bois de structure - Dimensions, écarts admissibles

La présente norme européenne spécifie deux classes d'écarts admissibles par rapport à des dimensions cibles pour les bois de structure en essences résineuses et feuillues.
Elle définit également la teneur en humidité à utiliser comme référence pour la mesure des dimensions et donne les valeurs moyennes des variations dimensionnelles dues aux variations de teneur en humidité.
Elle s’applique aux bois de structure avivés sciés et ébauchés ayant des rives parallèles et des épaisseurs ou largeurs supérieures à 6 mm.

Konstrukcijski les - Mere, dovoljena odstopanja

Ta evropski standard določa dva razreda dovoljenih odstopanj od ciljnih mer za konstrukcijski les mehkih in trdih vrst. Določa tudi vsebnost vlage, ki se uporablja kot referenčna točka za merjenje mer, ter navaja povprečne vrednosti za spremembe mer zaradi sprememb vsebnosti vlage. Uporablja se za žagan in pripravljen konstrukcijski les s kvadratnim robom z vzporednimi robovi z žaganimi debelinami ali širinami nad 6 mm.

General Information

• Status: Published
• Public Enquiry End Date: 29-Jun-2012
• Publication Date: 06-Nov-2013
• ICS: 79.040 - Wood, sawlogs and sawn timber
• Technical Committee: KON.005 - Timber structures
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 03-Oct-2013
• Due Date: 08-Dec-2013
• Completion Date: 07-Nov-2013
• Ref Project: EN 336:2013 - Structural timber - Sizes, permitted deviations

Relations

• Replaces: SIST EN 336:2004 - Structural timber - Sizes, permitted deviations
• Effective Date: 01-Dec-2013

Overview

SIST EN 336:2013 is a European standard developed by CEN that specifies the sizes and allowable deviations for structural timber. It applies to both softwood and hardwood species used in construction and structural applications. The standard defines target sizes at a reference moisture content of 20% and details two tolerance classes for permitted dimensional deviations. It covers sawn and prepared square-edged structural timber with thicknesses or widths greater than 6 mm.

This specification ensures uniformity and quality in structural timber dimensions, facilitating interoperability and reliability in timber engineering and construction projects across Europe.

Key Topics

• Scope and Applicability
  SIST EN 336:2013 applies to structural timber with parallel edges used in load-bearing applications, including timber sections thicker than 6 mm. It is relevant for both softwood and hardwood species.

• Target Size and Moisture Content
  Dimensions are specified based on a reference moisture content of 20%. The standard provides guidelines on how timber size changes with moisture content variations:

  • Softwoods and poplar: thickness and width increase or decrease by 0.25% per 1% change in moisture content from 20% (up to 30%).
  • Hardwoods: thickness and width change by 0.35% per 1% moisture content change.

• Permitted Deviations
  Two tolerance classes define permitted deviations from target sizes:

  • Tolerance Class 1 (wider tolerances for general applications):
    • Thickness/width ≤ 100 mm: -1 mm / +3 mm
    • 100 < thickness/width ≤ 300 mm: -2 mm / +4 mm
    • Thickness/width > 300 mm: -3 mm / +5 mm
  • Tolerance Class 2 (narrower tolerances for precise applications):
    • Thickness/width ≤ 100 mm: -1 mm / +1 mm
    • 100 < thickness/width ≤ 300 mm: -1.5 mm / +1.5 mm
    • Thickness/width > 300 mm: -2 mm / +2 mm

• Measurement Standards
  Dimensions should be measured following EN 1309-1, and moisture content determined using EN 13183 parts 1, 2, or 3, ensuring consistency in assessment methods.

• Length Deviations
  Negative length deviations (shorter than target length) are not allowed. Overlengths should be controlled via contractual agreements.

Applications

SIST EN 336:2013 is essential in multiple practical fields involving structural timber, including:

• Construction Engineering
  Ensures timber components meet strict dimensional accuracy for load-bearing elements, supporting structural integrity and safety.

• Timber Manufacturing
  Provides standardized size tolerances for sawn and prepared timber products enabling quality control and conformity across manufacturers.

• Quality Assurance and Inspection
  Assists inspectors and engineers in verifying timber sizes against established tolerances, factoring in moisture-induced size changes for accurate assessment.

• Architectural Design
  Facilitates the design of timber structures with predictable, reliable component dimensions, supporting modular construction and material optimization.

• Timber Trade and Procurement
  Enables clear communication of size expectations and tolerances between suppliers and buyers, reducing disputes and enhancing supply chain efficiency.

Related Standards

• EN 1309-1 – Method of measurement of dimensions for sawn timber, guiding accurate size measurement techniques.
• EN 13183 (Parts 1, 2, 3) – Standards for moisture content determination by oven dry, electrical resistance, and capacitance methods.
• EN 14298 – Sawn timber drying quality assessment, relevant for understanding and controlling moisture-related changes.
• EN 1995 (Eurocode 5) – Design of timber structures, where SIST EN 336:2013 ensures compliance of materials used.

By adhering to SIST EN 336:2013, stakeholders throughout the timber construction value chain can ensure structural timber components meet consistent size specifications with reliable quality, supporting safer, more efficient, and standardized timber engineering practices across Europe.

Standards Content (Sample)

SLOVENSKI STANDARD
01-januar-2014
1DGRPHãþD
SIST EN 336:2004
Konstrukcijski les - Mere, dovoljena odstopanja
Structural timber - Sizes, permitted deviations
Bauholz für tragende Zwecke - Maße, zulässige Abweichungen
Bois de structure - Dimensions, écarts admissibles
Ta slovenski standard je istoveten z: EN 336:2013
ICS:
79.040 Les, hlodovina in žagan les Wood, sawlogs and sawn
timber
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 336
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2013
ICS 79.040 Supersedes EN 336:2003
English Version
Structural timber - Sizes, permitted deviations
Bois de structure - Dimensions, écarts admissibles Bauholz für tragende Zwecke - Maße, zulässige
Abweichungen
This European Standard was approved by CEN on 24 August 2013.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same
status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2013 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 336:2013: E
worldwide for CEN national Members.

Contents Page
Foreword .3
Introduction .4
1 Scope .5
2 Normative references .5
3 Terms and definitions .5
4 Sizes for structural timber .5
4.1 General .5
4.2 Changes in size due to changes in moisture content .6
4.3 Permitted cross-sectional deviations .6
4.4 Permitted length deviations .6
5 Moisture content measurement .6
Bibliography.7

Foreword
This document (EN 336:2013) has been prepared by Technical Committee CEN/TC 124 “Timber structures”, the
secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an identical text or
by endorsement, at the latest by April 2014, and conflicting national standards shall be withdrawn at the latest by
April 2014.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights.
CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document will supersede EN 336:2003.
Compared to EN 336:2003, the following modifications have been made:
a) in the scope, the limit to 300 mm is deleted so the standard is available for large cross section;
b) minimum size changed from 22 mm to 6 mm;
c) in subclause 4.2, the changes in size due to changes in moisture content are given for hardwoods;
d) in subclause 4
...