EN 17121:2019

SLOVENSKI STANDARD
01-december-2019
Ohranjanje kulturne dediščine - Zgodovinske lesene konstrukcije - Smernice za
ocenjevanje nosilnih lesenih konstrukcij na kraju samem
Conservation of cultural heritage - Historic timber structures - Guidelines for the on-site
assessment of load-bearing timber structures
Erhaltung des kulturellen Erbes - Historische Holzkonstruktionen - Leitlinien für die
Bewertung vor Ort von tragenden Holzkonstruktionen
Conservation du patrimoine culturel - Structures en bois du patrimoine - Lignes
directrices relatives à l’évaluation sur site des stuctures porteuses en bois
Ta slovenski standard je istoveten z: EN 17121:2019
ICS:
91.080.20 Lesene konstrukcije Timber structures
97.195 Umetniški in obrtniški izdelki. Items of art and handicrafts.
Kulturne dobrine in kulturna Cultural property and
dediščina heritage
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 17121
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2019
EUROPÄISCHE NORM
ICS 91.080.20; 97.195
English Version
Conservation of cultural heritage - Historic timber
structures - Guidelines for the on-site assessment of load-
bearing timber structures
Conservation du patrimoine culturel - Structures en Erhaltung des kulturellen Erbes - Historische
bois du patrimoine - Lignes directrices relatives à Holzkonstruktionen - Leitlinien für die Bewertung vor
l'évaluation sur site des stuctures porteuses en bois Ort von tragenden Holzkonstruktionen
This European Standard was approved by CEN on 1 July 2019.

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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 17121:2019 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Assessment procedure . 8
4.1 General . 8
4.2 Preliminary assessment . 9
4.3 Desk study . 11
4.4 Historical analysis . 11
4.5 Preliminary visual survey . 12
4.6 Measured survey . 12
4.7 Structural analysis . 13
4.8 Preliminary report . 14
5 Detailed survey . 15
5.1 Overview . 15
5.2 General . 15
5.3 Identification of wood species . 16
5.4 Estimating wood moisture content and moisture gradients . 16
5.5 Characterization of biological damage . 16
5.6 Strength assessment of timber . 17
5.7 Wood dating . 18
5.8 Detailed survey of timber joints . 19
5.9 Detailed structural analysis . 20
Annex A (informative) Tools for non-destructive analyses on timber structures . 21
Bibliography . 27

European foreword
This document (EN 17121:2019) has been prepared by Technical Committee CEN/TC 346 “Conservation
of Cultural Heritage”, the secretariat of which is held by UNI.
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 March 2020, and conflicting national standards shall be
withdrawn at the latest by March 2020.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United
Kingdom.
Introduction
The purpose of the present document is to consider condition survey and diagnostic methods for
assessing heritage load-bearing timber structures with a view to establishing safe working loads or
determining the need for strengthening or repair in order to ensure their continuing use.
Heritage structures are important historic artefacts, which differ from other existing structures in that a
greater value is placed on their fabric because of their historical significance. It is necessary to gather data
in order to be able to assess the ability of such a structure to carry the required loads and continue to be
in use both now and for the foreseeable future, and to identify those areas of the structure that require
repair or strengthening. Both the conduct of the survey, assessment and any subsequent repair or
strengthening that could be necessary should involve minimum intervention. This could justify greater
expense both in the survey, diagnosis and assessment of the structure and in the consideration of the
repair methods that might be employed. The assessment of their condition and of their existing structural
characteristics is expected to be state of the art, which might require the use of more precise methods
than those that are used for other existing structures, with a cost that could not otherwise be justified.
Moreover intervention works (repair or strengthening) should only be carried out to a heritage structure
as a last resort and should have minimal impact on the building fabric (the original materials, structural
systems and techniques).
An important part of the work involves the documentation and understanding of the history of a
structure: loads, construction technology, and the period’s aesthetic details in order to be able to assess
the historical significance of either the overall structure or of any of its components. Historical
significance of a structure could relate to the history of the structure itself or that of the building of which
it is a part. Such understanding requires an interdisciplinary approach with any other profession that can
be helpful to the assessment procedure.
In some cases, where the problems are simple and obvious, the preliminary, visual survey might be all
that is required but in general a more detailed survey will be needed .

The survey of existing buildings to determine their suitability for continuing use or for a change of use has been
considered by ISO 13822. Annex I of that standard considers heritage structures.
1 Scope
This document gives guidelines on the criteria to be used for the on-site assessment of load-bearing
timber structures in heritage buildings. It is intended for all those concerned with the conservation of
heritage buildings which contain wooden elements, from the building owners or authorities who are
responsible for them to the professionals employed. It should also help decision-making regarding the
need for immediate measures. Its aim is to guarantee that condition survey and assessment provide the
necessary data for historical analysis, structural safety assessment and planning of intervention works.
This document is applicable to any kind of timber member and to any kind of historic timber structures.
It is not applicable to timber members made of engineered wood based panels and glued laminated
timber.
This document provides a comprehensive procedure for the on-site assessment. With a practical and
technical evaluation of the damage found and based on the responsibility of the involved professionals, a
sufficient assessment can also be made when not all the steps are followed.
In each different country, the document is expected to be applied in accordance with National legislation
and regulations.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 335, Durability of wood and wood-based products — Use classes: definitions, application to solid wood
and wood-based products
EN 1912, Structural Timber — Strength classes — Assignment of visual grades and species
EN 1995-1-1, Eurocode 5: Design of timber structures — Part 1-1: General — Common rules and rules for
buildings
EN 14081-1:2016, Timber structures — Strength graded structural timber with rectangular cross
section — Part 1: General requirements
EN 16085, Conservation of Cultural property — Methodology for sampling from materials of cultural
property - General rules
EN 16096, Conservation of cultural property — Condition survey and report of built cultural heritage
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 14081-1, EN 1912 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
action
set of forces (loads) applied to the structure
[SOURCE: EN 1990:2002, 1.5.3.1, modified]
3.2
alteration
change in condition, beneficial or not, intentional or not
[SOURCE: EN 15898:2011, 3.2.4]
3.3
biological damage
damage caused by living organisms such as fungi and insects
Note 1 to entry: In load bearing timber structures, the damage is considered in terms of reduction of the
effective cross-section.
3.4
condition survey
inspection to assess the condition of the structure
[SOURCE: EN 15898:2011, 3.6.4, modified]
3.5
critical area/zone
part of a timber element over a length of 150 mm, or equal to the depth of the member, whichever is the
greater, which is considered to
...