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Buildings envelope anomalies: A visual survey methodology
M. Fernanda S. Rodrigues
a,
⇑
, José M.C. Teixeira
b
, José C.P. Cardoso
a
a
University of Aveiro, Civil Engineering Department, Campus Universitário de Santiago, Aveiro, Portugal
b
University of Minho, Civil Engineering Department, Campus de Azurém, Guimarães, Portugal
a r t i c l e i n f o
Article history:
Received 18 November 2009
Received in revised form 6 December 2010
Accepted 16 December 2010
Available online 8 January 2011
Keywords:
Visual survey methodology
Social housing
Anomalies
Degradation level
Performance level
a b s t r a c t
The early deterioration of social housing envelopes reflect their low durability. An evaluation methodol-
ogy to estimate social housing envelope degradation level was developed which has been applied to a set
of social housing. Following this study, the methodology revealed adequate for any sort of buildings, tak-
ing into account their specific features that necessitate some methodology modifications. To support the
visual survey of the external building envelope, tables applying the Failure Mode and Effects Analysis
(FMEA) were used to analyse the principal causes and effects of the anomalies identified. To evaluate
the main visible anomalies on their external envelope, two evaluation scales have been created: one
for the degradation degree applicable to each typified anomaly and the other for the performance level
of each building respect to a set of functional requirements. The degradation level of each of the principal
anomalies was determined as well as the evaluation index of the building envelope. Degradation evalu-
ation results were obtained through visual survey and were aggregated by two methods developed for
the research: one based on the Hermione aggregation method and the other on the results of the inquiry
to tenants based on a multi-attribute analysis attending to the relatively importance (weight) of the eval-
uated requirements. Each attributed weight was obtained throughout the expressed opinion of techni-
cians and specialists from the construction sector.
The aim of this paper is to present the visual survey methodology of the envelope degradation level and
the results obtained for the degradation degree of each typified anomaly, and the performance level of
each building in respect of a set of functional requirements.
Ó2010 Elsevier Ltd. All rights reserved.
1. Introduction
The degradation of buildings’ envelope is one of the main con-
cerns of owners and is frequently the root cause of rehabilitation
actions that can improve their external appearance [1]. Indeed
buildings image is closely related to the quality and durability of
their envelope, the decay of which causes negative evaluation
and rejection by users. The quality of design and construction is
essential to prevent early decay and ageing of the buildings exter-
nal envelope. Therefore the buildings envelope must ensure high
durability and resistance to external environmental agents and
enable high standards of internal comfort for users (thermal,
acoustical, air quality, lighting, etc.). Because of the substantial
investments that are continually being made in social dwellings,
it is essential to carefully pick the best possible design and con-
struction options for the external envelope of these buildings. Ade-
quate solutions must balance costs, performance and quality so
that they may be economical and long lasting thus leading to the
lowest possible total costs, measured in terms of initial costs and
maintenance costs throughout the project life. This applies both
to new buildings and to existing buildings needing rehabilitation
of their external envelope [2].
In the 1970s the Japanese government, owner of a huge stock of
social homes, started facing the problems of maintaining and reha-
bilitating buildings evidencing early degradation symptoms.
Several studies were developed on this topic and a rehabilitation
guide was published in 1989, translated into English in 1993
1
[3].
The guide indicates the factors to consider for selecting the best
possible rehabilitation options for increasing buildings durability.
Relevant steps of the proposed methodology obviously include mea-
suring the performance of buildings and their level of degradation.
Beyond the Japanese studies, several other similar initiatives have
been developed elsewhere [4] therefore reflecting the importance
of this topic.
In Portugal, the results of the 2001 Census show that there is a
substantial number of housing buildings needing repair and reha-
bilitation [5]. Moreover, the census displays qualitative and quan-
titative data on the level of conservation or degradation of all
buildings surveyed but it is not specific for social housing units
0950-0618/$ - see front matter Ó2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.conbuildmat.2010.12.029
⇑Corresponding author. Tel.: +351 234370049; mobile: +351 967644055; fax:
+351 234370094.
E-mail address: mfrodrigues@ua.pt (M.F.S. Rodrigues).
1
Principal Guide for Service Life Planning of Buildings [3].
Construction and Building Materials 25 (2011) 2741–2750
Contents lists available at ScienceDirect
Construction and Building Materials
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c o n b u i l d m a t
[5,6]. However, evaluating performance and degradation level of
buildings as well as predicting their future evolution is essential
for deciding the repair and rehabilitation requirements [5].
This article presents a methodology for the visual survey of the
main anomalies of the external envelope of buildings. The method-
ology was applied to a set of dwellings in Portugal
2
and this
allowed identification of the main visible anomalies on their external
envelope. In order to achieve this, two evaluation scales have been
built: one for the degree of degradation applicable to each typified
anomaly and the other for the performance level of each building re-
spect to a set of functional requirements. The degradation level (DL)
of each anomaly was established and results for all typified anoma-
lies were subsequently aggregated yielding the evaluation index (EI)
of the external envelope of each surveyed building. The visual survey
included the assessment of their external envelope and internal sur-
veys and interviews in about 15% of the apartments. The aim of the
survey is to obtain for each building global degradation and perfor-
mance levels [7].
2. Buildings anomalies
2.1. Building deterioration
According to Harris [8], the decay noticed in buildings is a nat-
ural process and unavoidably takes place in time, not being neces-
sarily the result of design error or construction deficiency. In fact
the mechanisms of deterioration are the consequence of the inter-
action of two independent variables: the building, as a physical ob-
ject and the environment, as a source of agents. The building starts
decaying immediately after construction, starting with materials in
an invisible way. This is the incipient stage – deterioration takes
place but with no visible damage. The second stage is the fast dete-
rioration – mechanisms started before aggregate and become visi-
ble. Shortly afterwards, the building components start failing,
culminating with total building failure and eventual abandonment.
Although the degradation of building components is a normal con-
sequence of the ageing process, there is a set of factors influencing
that process, such as building quality, weather conditions, lack of
maintenance, and so on. These factors will increase the building
operation costs and expand the rehabilitation needs, if no actions
are taken to halt the degradation process. Actions include mainte-
nance, repair and rehabilitation that must be applied to the build-
ing elements. The duration of the built elements depends not only
on their physical, chemical and mechanical properties but also on
the maintenance conditions and environmental exposure they are
subjected to [9]. In order to establish the building degradation level
two sets of factors must be taken into consideration – the durabil-
ity conditions of the building and the degradation factors acting
upon it – both of which contribute to trigger the degradation pro-
cess [3].
During their service life buildings must comply with an assort-
ment of requirements that can be grouped as: functional, perfor-
mance, legal and users requirements [10].
The principles for repair, rehabilitation and maintenance
actions must: meet the terms of the legal requirements applied,
facilitate future interventions (including written registrations, for
example, related to safety at work), and fulfil the functional, per-
formance and users requirements. It is essential that these inter-
ventions contribute to eliminate or reduce the degradation level,
improving the building performance and optimizing its service life.
The ISO 6241:1984 standard contains, in categories, the various
users requirements that buildings must fulfil during their service
life, applicable to the indoor spaces or to the envelope, indepen-
dently of their location or conception, for all the buildings or their
parts (Table 1 of [11]). The ISO 15686-1:2000 standard also pre-
sents these requirements synthetically in its Annexe D [12].
According to these standards, principal requirements can be de-
fined to be applied to the building envelope: stability, fire safety,
air and water waterproofing, indoor thermal and acoustic comfort,
durability and maintainability, economics and visual aspect. It
must be noted that several degradation factors contribute to de-
crease the buildings’ durability.
2.2. Main building anomalies
Data on causes of building anomalies is scarce in Portugal but
the literature survey on this topic has shown identical conclusions
extracted from several sources [13], so it seems acceptable to con-
sider it representative of the Portuguese reality as well [14]. The
analysis of this survey [13] shows that the main sources of anom-
alies are design errors, followed by construction problems and
with material deficiencies in third place. These results basically
agree with the general conclusion one can take by randomly ana-
lysing building construction in Portugal, although they contradict
the general conviction that the main causes lie in the construction
process. However, in March 2006 the Agence Qualité Construction,
published a report on construction quality in France from 1995 to
2005 and concluded that a lower number of anomalies were
caused by design, assigning about 80% of anomalies detected in
buildings to construction causes [15].
The incidence of anomalies on the external envelope of build-
ings appears to have a great importance. According to several
sources of data [5,10,15–19], about 50% of anomalies recorded neg-
atively affect the external building envelope. Moreover, according
to a survey of BRE [16], these anomalies directly contribute to
the decrease of about 50% in the performance of important build-
ing functional requirements (waterproofing, durability and main-
tenance) and substantially influence others (thermal insulation
and acoustic performance) in over 10% of related requirements.
The work of BRE further identified a set of anomalies of the exter-
nal building envelope: water penetration, condensation, humidity,
cracking, detachment, noise transmission and visual deterioration,
among others.
The effect of anomalies in building envelope is the decrease of
performance of their functional requirements and the increase of
investment needed in corrective actions for repair and rehabilita-
tion. Therefore the prediction of emerging anomalies and building
performance evolution are key factors for establishing mainte-
nance and rehabilitation strategies for the housing stock. Indeed,
the large weight of maintenance costs of facades when compared
to the total maintenance costs of buildings evidences the need
for sound prediction of the former in order to decrease the latter
[20].
3. Envelope evaluation scales: literature review
Several methodologies have been developed for evaluating
anomalies of the building envelope. In order to collect statistical
data on the building ‘‘conservation state’’ for the Portuguese census
of 2001, a ‘‘repair needs’’ record was created [5,6]. A special scale
had previously been developed [21] for that purpose although it
did not consider the causes of the anomalies detected. Another
method was developed in Portugal for evaluating the conservation
level of dwellings and setting up rental fee update factors [22] but
it does not consider causes for anomalies either.
2
Buildings surveyed were erected under the low cost regime (cost controlled
system that allows for public co-financing), in the Aveiro district after 1971 and are
rented (in the public renting system that comprises social benefits to tenants) and are
currently managed by the local municipality.
2742 M.F.S. Rodrigues et al. / Construction and Building Materials 25 (2011) 2741–2750
The extent of damages is another important issue for which
some type of measurement scale is required. Several qualitative
scales have been developed and become widely known, such as
[23]. Other scales for graduating building envelope anomalies have
also been found in the literature [24–29]. Based on this survey, the
research project supporting this article [7] developed an evaluation
scale, specific to the reality surveyed as described below.
Finally, a number of evaluation methods for measuring the
building performance and subsequently supporting the decision
of corrective measures have also been found in the literature, basi-
cally falling under the following classes [9]:
Multi-Attribute Decision Aid (MADA).
Quality Function Deployment (QFD) method.
Risk Analysis.
4. Methodology
4.1. Overview
The evaluation of the degradation level of the external envelope
of buildings surveyed was based on visual survey and interviews
to: a group of tenants, the asset managers from local authorities,
the person in charge of the building current management. This
has been used in the scope of a research project on prioritising
refurbishment interventions in the Portuguese social housing stock
[7].
Using visual survey for building anomaly assessment has been
extensively reported in the literature with special emphasis on
the EPIQR methodology that combines visual survey with inquiries
to tenants and visits to their apartments [30]. Similarly, the survey
performed in this project comprised visual survey of the external
building envelopes and visits to at least three apartments in each
building, preferably located in different facades and on different
floor levels (one on the ground floor or first floor, another on the
top floor and the last on an intermediate floor). Common areas of
each building have also been looked at [30,31].
The visual survey was adequate for the dimension of the sample
under analysis [25] and revealed to be a straightforward, easy to
use and low cost approach. The aims of the visual survey were to
identify anomalies, assess their level of severity, gauge their root
causes and suggest correcting measures. The severity level was as-
sessed through evaluation scales, the deterioration parameters of
which had previously been defined. Evaluation methods used in
buildings generally point to the assessment of each building ele-
ment taken separately, typically through five degradation or per-
formance levels [25].
Interviews comprised visit to each tenant home to check anom-
alies previously reported by them, assigning a sound graduation le-
vel to those anomalies, complementing the external survey.
Moreover, interviews also helped in assessing the quality of the
internal environment of houses by enabling the detection of ther-
mal and acoustic pitfalls.
The approach followed in the diagnosis was previously
prepared and normalized for the whole set of buildings surveyed,
enabling a reliable evaluation of their external envelope, setting
up adequate rehabilitation actions and establishing corrective
measures for the improvement of energy efficiency and internal
air quality.
4.2. Visual survey support
To support the visual survey of the external building envelope,
tables applying the Failure Mode and Effects Analysis (FMEA), were
used to analyse the principal causes and effects of the identified
anomalies. The aim of this analysis is to identify the degradation
types that can affect the envelope as the deterioration chains de-
velop (Table 1).
This method allows to find the relationship between the deteri-
oration state of the analysed elements and their performance level.
It has especially been applied to obtain the service life cycle and
degradation models of construction systems and products. In each
case the failure mode represents the degradation process [32]. It is
based on an interactive principle: the direct or indirect effects can
become the causes of other degradations, giving the possibility of
identifying almost all the possible failure modes of the analysed
element or product. The FMEA will be complete when all the pos-
sible degradation chains lead to the components or products fail-
ure (the failure is obtained when one of its principal functions
are not more fulfilled) [33].
Through this method the main failure modes have been identi-
fied, as well as their causes and direct and indirect effects on: tra-
ditional plasters (cement mortar covering), single-coat render
mortar, ceramic tiles covering, painting coatings, ceramic roof-
tiles, fibro-cement roof-tiles, flat roof systems and frameworks
with simple glazing, as in the example presented in Table 2.
The different failure modes, causes and effects, of these con-
structive elements have been systematized supported by literature
review, as exhaustively as possible. So, these tables show failure
mode causes and effects whose assessment can not be conducted
only by visual inspection.
4.3. Evaluation scale
The visual survey supported by FMEA was measured through a
qualitative and quantitative evaluation scale. The aim was to quan-
tify the identified external anomalies by their level of severity by
Table 1
Observation table structure – FMEA.
Element Function Failure
mode
Causes Direct
effects
Indirect
effects
Table 2
Observation table structure – FMEA: Application.
Element Function Failure mode Causes Direct effects Indirect effects
Rain water
drainage
systems
Waterproofing The rain water drainage system is non existent,
insufficient or shows functional deficiencies
Conception and
maintenance
anomalies
Infiltrations and spilling Diverse secondary
anomalies can be
originated by water
infiltration
External
visual aspect
The rain water drainage systems present
elements with covering wearing out, corrosion,
broken or disconnected
Maintenance
anomalies
Deficient exterior visual aspect,
spilling, due to disconnected and
broken elements
Durability reduced
Diverse secondary
anomalies due to possible
water infiltration
Other pathologies
M.F.S. Rodrigues et al. / Construction and Building Materials 25 (2011) 2741–2750 2743
means of an evaluation scale. The scale makes use of deteriora-
tion parameters for each level, by associating a visual scale with
a physical scale, similar to the scale used by Shohet and Paciuk
[29]. The assessment takes into account the intensity, extension
and location of damages detected. Table 3 shows the eight level
evaluation scale used in the survey. This was set up on the basis
of the Hermione scale [9,34], the lowest level of which (R) was
condensed to two levels with the following meanings: R
+
for
unacceptable degradation cases where rehabilitation is still possi-
ble through exceptional rehabilitation actions, and R°for very se-
vere situations.
It was decided to assess the following functional requirements:
waterproofing of the envelope (roof, external walls and
frameworks);
external visual aspect (covering cracks, detachment, diffusion of
vegetation and micro organisms, broken glazing, degradation of
roof and rain water drainage system);
durability.
Table 3
Evaluation level.
Fig. 1. Visual and physical evaluation scale description.
2744 M.F.S. Rodrigues et al. / Construction and Building Materials 25 (2011) 2741–2750
For each of the eight levels of the graduation scale the evalua-
tion requirements have been specified to be applied to each of
the observed elements. These evaluation requirements were de-
fined by the conjugation of different evaluation scales described
in the literature analysed. The developed evaluation scales are in-
tended to be an evaluation instrument of the building’s envelope
degradation level, which considers the identified degradation phe-
nomenon intensity, associated to its extension and location.
To make the visual observation easier the referred scale was
illustrated with reference to the extension and location of the
anomalies for each of the evaluated elements. Fig. 1 depicts an
example of degradation level 10.
The evaluation levels depicted in Table 3 were associated in the
observation tables (Tables 1 and 2) as shown in Table 4.
The facades main anomalies identified were: covering discol-
ouring and detachment, cracks, efflorescence spots and dark spots
(mainly due to micro organisms culture and dirt remains), damp-
ness (mainly due to rain water absorption and ascending humid-
ity). During the inhabitants interviews and the indoor dwellings
inspections, waterproofing anomalies were registered.
From the frameworks visual inspections the following elements
were detected: broken and warped (hard to open), with covering
wearing out or corroded. During the inhabitants’ interviews and
the indoor dwellings inspections waterproofing and air permeabil-
ity anomalies were registered as operational disruptions.
The rain water drainage systems presented elements with cov-
ering wearing out, corrosion, that were broken or disconnected.
During the inhabitants’ interviews the insufficient drainage capac-
ity was registered.
The roof anomalies are mostly in situations impossible to ob-
serve directly. Their evaluation was achieved through indirect indi-
cators related to waterproofing mentioned by the inhabitants such
as: infiltrations and roof covering, roof elements damaged or miss-
ing. Roof direct observation was conducted in all possible situa-
tions and the following were registered: damaged and inexistent
elements, incorrect or inexistent roof closings, deformed roof
surface, spread of vegetation and accumulated detritus. Table 5
shows the synthesis of the direct visual observations and the indi-
rect evaluations.
4.4. Aggregation of results
Results from the visual evaluation were aggregated into a global
value for each element and/or anomaly surveyed. The aggregation
approach adopted for that purpose was first based on the Hermione
qualitative method [34] but it was later concluded that it should be
modified into a quantitative method, for which eight graduation lev-
els were adopted. Accordingly, a method was constructed that al-
lows the obtaining of a global degradation level for each element
and/or anomaly surveyed by aggregating the graduations assigned
to each area or element examined on the external envelope of build-
ings. Moreover, departing from these results, the degradation level
was assigned to each building’s envelope.
Table 6 shows the collection of aggregation conditions devel-
oped for each of the eight evaluation levels.
So, a model was implemented that allows to obtain a global
degradation level value. By aggregating the graduations given to
the anomalies of the areas/elements observed a global value is
reached for each area/element (see an application example in Table
7a), and by aggregating these values the global degradation level of
the building envelope, named evaluation index (EI), is also
achieved (see Table 7b).
4.5. Interviews
4.5.1. Background
The real building degradation level is not achieved only by its
envelope visual survey. Indoor deterioration factors also must be
observed and both internal and external surveys must be comple-
mented with tenants interviews [30]. To complement the envelope
visual survey and to arrive at the performance level of the building
through the interior and exterior anomalies referred to by tenants,
Table 4
Observation tables with the evaluation scale associated.
Note: E – exist; NE – not exist.
Table 5
Observation synthesis.
Envelope element Evaluation through direct visual observation Indirect evaluation through inhabitants’ interviews
Facades Covering Discolouring Waterproofing
Covering detachment
Covering cracks
Dark spots mainly due to micro organisms culture and dirt remains
Efflorescence spots
Moisture spots
Frameworks Broken elements Waterproofing
Warped elements Air permeability
Covering wearing out
Rain water drainage systems Missing elements Drainage capacity
Broken elements System obstruction
Corrosion
Covering wearing out
Roof Missing elements Waterproofing
Broken elements
Inexistent roof closings
Deformed roof surface
Spread of vegetation and detritus
M.F.S. Rodrigues et al. / Construction and Building Materials 25 (2011) 2741–2750 2745
a previously normalized graduation was attributed to each answer
of the prepared questionnaire. These were prepared according with
the performance requirements that had been identified to be eval-
uated. The purpose is to obtain a global classification for each of
the specified requirements and for the entire building.
4.5.2. Evaluation requirements
To implement the interviews a matrix was constructed which
defines the requirements to be evaluated in accordance with the
users chosen functional requirements. These requirements were
identified with reference to:
Table 6
Aggregation synthesis – developed method.
Table 7a
Aggregation of anomalies of building envelope.
DL Covering detachment Micro organisms Frameworks
Number Percentage Aggregation Number Percentage Aggregation Number Percentage Aggregation
10 0 0 FALSE 0 0 FALSE 0 0 FALSE
9 8 66.67 DL = 9 1 8.33 FALSE 0 0 FALSE
8 4 33.33 FALSE 1 8.33 FALSE 0 0 FALSE
7 0 0 FALSE 6 50 FALSE 0 0 FALSE
6 0 0 FALSE 2 16.67 DL = 6 0 0 DL = 5
5 0 0 FALSE 1 8.33 FALSE 11 91.67 FALSE
4 0 0 FALSE 1 8.33 FALSE 1 8.33 FALSE
3 0 0 FALSE 0 0 FALSE 0 0 FALSE
Total 12 100 12 100 12 100
DL Dark Spots Efflorescence Spots Roof
Number Percentage Aggregation Number Percentage Aggregation Number Percentage Aggregation
10 0 0 FALSE 0 0 FALSE 0 0 FALSE
9 0 0 FALSE 10 83.33 DL = 9 0 0 FALSE
8 0 0 FALSE 2 16.67 FALSE 4 30.77 FALSE
7 0 0 FALSE 0 0 FALSE 0 0 FALSE
6 4 33.33 DL = 5 0 0 FALSE 9 69.23 DL = 6
5 8 66.67 FALSE 0 0 FALSE 0 0 FALSE
4 0 0 FALSE 0 0 FALSE 0 0 FALSE
3 0 0 FALSE 0 0 FALSE 0 0 FALSE
Total 12 100 12 100 13 100
DL Covering discolouring Rain water drainage systems Covering cracks
Number Percentage Aggregation Number Percentage Aggregation Number Percentage Aggregation
10 0 0 FALSE 0 0 FALSE 0 0 FALSE
9 1 8.33 FALSE 0 0 FALSE 0 0 FALSE
8 0 0 FALSE 0 0 FALSE 8 30.77 FALSE
7 6 50 FALSE 0 0 FALSE 0 0 FALSE
6 3 25 DL = 6 0 0 DL = 5 10 38.46 DL = 6
5 1 8.33 FALSE 4 80 FALSE 8 30.77 FALSE
4 1 8.33 FALSE 1 20 FALSE 0 0 FALSE
3 0 0 FALSE 0 0 FALSE 0 0 FALSE
Total 12 100 5 100 26 100
2746 M.F.S. Rodrigues et al. / Construction and Building Materials 25 (2011) 2741–2750
the users performance requirements established in the ISO
6241:1984 and ISO 15686-1:2000 statements [11,12], whose
performance directly or indirectly depends on the characteris-
tics and degradation state of the envelope (waterproofing,
indoor hydrothermal and external visual requirements);
the indoor requirements evaluation – waterproofing, hydro-
thermal and interior acoustics conditions – with regard to per-
formance requirements to be verified during the building
service life, as specified in ISO 15686-3:2000 statements [35];
the durability and maintainability evaluation, users functional
requirements as specified in ISO 6241:1984 and ISO 15686-
1:2000 statements, also must be verified as performance
requirements during the building service life, according to ISO
15686-3:2000 statements [11,12,35]. The durability and main-
tainability requirements permit verification if the applied
materials and constructive elements present durability charac-
teristics that enable reliability during the building service life.
Or on the contrary they register a fast degradation and
consequent earlier repair and substitution requirement. More-
over the difficulty of implementing conservation actions
required by the higher or lower durability must be evaluated
(equipments, specialized work force, costs, . . .), as well as the
safety hazards to workers and third persons and the environ-
mental risks: the availability and maintainability [36]. These
subjects’ evaluation and treatment are of greater importance
in the design phase than in the planning of conservation and
rehabilitation actions, as they are associated with cost reduction
during the building’s service life.
Therefore a matrix was constructed with the principal require-
ments to be evaluated. Each of the secondary requirements was
also stated as shown in Table 8. The aim of this methodology is
to arrive at the global performance level of each principal require-
ment and thus the global performance evaluation of the entire
building.
Table 7b
Aggregation of anomalies DL to obtain the building envelope EI.
DL EI
Number Percentage Aggregation
10 0 0 FALSE
9 2 22.22 FALSE
8 0 0 FALSE
7 0 FALSE
6 4 44.44 EI = 6
5 3 33.33 FALSE
4 0 0.00 FALSE
3 0 0 FALSE
Total 9 100
Table 8
Interviews – Evaluation requirements.
Principal requirements Secondary requirements Users requirements (ISO 6241-1:1984
e ISO 15686-1:2000)
Performance requirements
(ISO 15686-3:2000)
1. Waterproofing 1.1. Roof waterproofing Waterproofing requirements
1.2. Facade waterproofing
1.3. Frameworks waterproofing
2. Indoor hydrothermal conditions 2.1. Summer thermal comfort Hydrothermal requirements
2.2. Winter thermal comfort
2.3. Indoor overheating
2.4. Indoor moisture
2.5. Indoor moisture spots
3. Indoor acoustics conditions 3.1. External aerial sound propagation Acoustics requirements
3.2. Indoor aerial sound propagation
3.3. Percussion sound propagation
4. Visual aspect of envelope 4.1. Covering cracks Exterior visual requirements
4.2. Covering discolouring
4.3. Covering detachment
4.4. Spots on facades (mainly due to micro organisms culture and
dirt remains)
4.5. Efflorescence spots
4.6. Moisture spots
4.7. Frameworks (broken glass, warped, fissured, porous sills,
without or with incorrect dripping-pan)
4.8 Inexistent/warped rain water drainage system, deteriorating,
corrosion, broken or missing elements
4.9. Roof covering/waterproofing/closing damaged and/or
incorrectly installed and/or with accumulated vegetation or other
debris
5. Durability and maintainability 5.1. Materials conservation (building/dwelling) Durability requirements
5.2. Constructive elements and facilities conservation (building/
dwelling)
5.3. Maintainability (envelope and common parts of the building)
Table 9
Weight scale (Adapted from MCDM-23 [38]).
Graduation (pi) Evaluator weight to be attributed according
to the relative importance degree (relative
to the most important requirement)
10 Equal importance
9
8 Less important
7
6 Strongly less important
5
4 Without importance
3
M.F.S. Rodrigues et al. / Construction and Building Materials 25 (2011) 2741–2750 2747
Moreover there are requirements that must be fulfilled
according to the statements, they also must be considered as
requirements to verify the indoor hydrothermal and acoustic con-
ditions and the durability and maintainability, as referred to in var-
ious building design quality evaluation methods, cited by Pereira
[37].
4.5.3. Multi-attribute analyses
The interviews with tenants were carried out by using multi-
attribute analysis supported by the graduation scale shown in
Table 10. It can be applied to any kind of problem in which deci-
sions must be taken supported by multiple requirements and
was set up on the basis of MCDM-23 [38].
After the definition of the principal and the secondary evalua-
tion requirements, a weight was attributed to each of these
requirements. This weight gives the relative degree of importance
of each requirement in the performance evaluation. It follows the
normalized weighted calculus for each of the secondary require-
ments (wi =pi/Ppi as explained in Table 12). The weight scale used
is shown in Table 9. It is equal to the evaluation scale to determine
the performance of each requirement in Table 10. In this way the
same scale values are used which permits a better treatment of
the results.
Tenants during the interviews were asked by the interviewer to
give an evaluation of each secondary requirement, whose valuation
had previously been normalized.
The final secondary requirement evaluation was obtained
through the product: Ci =wi ci (product of the normalized weight
and the attributed evaluation as explained in Table 12). The sec-
ondary requirements aggregation has been arrived at by the sum
of each weighted result, leading to the obtention of each principal
requirement evaluation [38]. This method was supported by Hier-
archic Analysis (AHP), developed by Saaty [39], and referred to by
several authors namely [40].
This method was applied to each secondary requirement level
to obtain the principal requirement classification, and again to
the principal requirements level to obtain the global building eval-
uation level [38]. Thus the global building classification relative to
the principal defined requirements was obtained through the fol-
lowing steps (Table 12):
weight attribution (pi) to the principal requirement according
to the values depicted in Table 9;
calculus of each principal requirement’s normalized weight
(Wi =pi/Ppi);
obtention of each principal requirement’s final classification –
Ci;
obtention of each principal requirement’s global classification–
Wi Ci;
obtention of global building classification – PWi Ci.
This global value represents, for the building, its performance
quality profile from the user perspective. This methodology was
supported by the Suisse method SEL – Systeme d’Evaluation de
Logements, cited by Pereira [37], used to achieve the ‘‘use value’’
of the building.
The values obtained are analysed and compared according to
the performance evaluation scale depicted in Table 10. This classi-
fication in conjunction with the building performance level, Table
11, leads to the different evaluation requirements’ performance le-
vel for the global building, as mentioned by tenants. It also permits
to arrive at a hierarchical building intervention.
5. Conclusions
The methodology enabled the development of tools for support-
ing the systematic visual survey of defects on the envelope of
buildings. The evaluation scale presented is an essential tool for
assessing the degradation level of the housing stock, therefore sup-
porting the degradation level and the performance level of
buildings.
The support visual observation matrix developed applying the
qualitative risks analysis methodology – FMEA (Failure Mode and
Effects Analysis), associated with the risk of the failure mode
occurrence graduation scale, will constitute an important instru-
ment to support designer teams. The development of this instru-
ment for other failure modes will support the reflection work of
the designer teams allowing these options to prevent determined
failure mode and future building anomalies. They will achieve this
goal through the correct option for durable constructive solutions,
with the establishment of performance requirements to be applied
during the design and the construction phase, and to be verified
during the use phase (by the user).
Finally, the importance of merging the evaluation of technicians
and residents was highlighted. The results that are not presented in
this paper, demonstrated that for the buildings surveyed, the
Table 10
Performance evaluation scale.
Valuation Performance level
(PL)
Exceptional without any intervention required. Plan maintenance actions to safeguard the conservation level. Completely satisfactory 10
Good without reservation. Regular cleaning and maintenance actions needed. Completely satisfactory 9
Good with some minor reservations. Cleaning and maintenance actions needed for the elements evidencing deterioration symptoms. Very
satisfactory
8
Acceptable but needing small rehabilitation actions. Satisfactory 7
Acceptable but needing moderate rehabilitation actions. Satisfactory 6
Acceptable but needing large rehabilitation actions. Partially satisfactory 5
Unacceptable. Priority intervention. Major rehabilitation. Unsatisfactory 4
Unacceptable. Unsuitable for rehabilitation. Demolish/substitute. Unsatisfactory 3
PL – performance level. Interviewers’ graduation.
Table 11
Building performance level (PL).
Excellent Very good Good Satisfactory Less than satisfactory Unsatisfactory
10 PPL P9 9 > PL P8 8 > PL P7 7 > PL P6 6 > PL P5 5 > PL P3
2748 M.F.S. Rodrigues et al. / Construction and Building Materials 25 (2011) 2741–2750
Table 12
Interviews matrix.
Principal requirements Secondary requirements Weights – pi (given by
the evaluator)
Normalized weight
wi =pi/piPPunctuation – ci (given by
the interviews)
Final classification
(wi)(ci)
1. Waterproofing 1.1. Roof waterproofing 10 0.33 9 3.00
1.2. Facade waterproofing 10 0.33 8 2.67
1.3. Frameworks waterproofing 10 0.33 5 1.67
Total requirement evaluation 30 1.00 7.33
2. Indoor hydrothermal
conditions
2.1. Summer thermal comfort 8 0.22 6 1.30
2.2. Winter thermal comfort 9 0.24 5 1.22
2.3. Indoor overheating 6 0.16 7 1.14
2.4. Indoor moisture 7 0.19 5 0.95
2.5. Indoor moisture spots 7 0.19 5 0.95
Total requirement evaluation 37 1.00 5.54
3. Accoustic conditions 3.1. External aerial sound propagation 6 0.27 4 1.09
3.2. Indoor aerial sound propagation 8 0.36 4 1.45
3.3. Percussion sound propagation 8 0.36 4 1.45
Total requirement evaluation 22 1 4.00
4. Visual aspect of the
envelope
4.1. Covering cracks 7 0.11 7 0.79
4.2. Covering discolouring 5 0.08 7 0.56
4.3. Covering detachment 7 0.11 8 0.90
4.4. Spots on facades (mainly due to micro organisms culture and dirt remains) 7 0.11 5 0.56
4.5. Efflorescence spots 5 0.08 7 0.56
4.6. Moisture spots 7 0.11 8 0.90
4.7. Frameworks (broken glass, warped, fissured, porous sills, without or with incorrect
dripping-pain)
8 0.13 5 0.65
4.8. Inexistence/warped rain water drainage system, wearing out, corrosion, broken
elements or missing elements
8 0.13 7 0.90
4.9. Roof covering/waterproofing/closeninddamaged and/or uncorrected done and/or
with accumulated vegetation or other debris
8 0.13 7 0.90
Total requirement evaluation 62 1.00 6.74
5. Durability and
maintainability
5.1. Materials conservation (building/dwelling) 7 0.32 5 1.59
5.2. Constructive elements and facilities conservation (building/dwelling) 8 0.36 5 1.82
5.3. Maintainability (envelope and common parts of the building) 7 0.32 5 1.59
Total requirement evaluation 22 1.00 5.00
Aggregation of each principal requirement evaluation Weights (given by the
evaluator) – pi
Normalized weight
wi =pi/piPFinal classification
Ci = (wi)(ci)
Global classification
(Wi)(P)
Waterproofing 10 0.25 7.3 1.83
Indoor hydrothermal conditions 9 0.23 5.5 1.25
Accoustic conditions 8 0.20 4.0 0.80
Envelope visual aspect 6 0.15 6.7 1.01
Durability and maintainability 7 0.18 5.0 0.88
Total 40 1.00 5.77
M.F.S. Rodrigues et al. / Construction and Building Materials 25 (2011) 2741–2750 2749
technicians were more concerned with technical consequences of
defects while the residents were more sensitive to living condi-
tions and comfort requirements.
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