Building façades maintenance support system

Abstract

This paper exemplifies the relevant aspects for the implementation of an adequate maintenance of façade coatings with a proactive perspective. Several modules that include technological (coatings pathology, preventive and corrective actions, inspection methods, urgent situation procedures, service life values) and economic (application, maintenance and replacement costs) aspects are characterized.

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XXX IAHS
World Congress on Housing
Housing Construction - An Interdisciplinary Task
September 9-13, 2002, Coimbra, Portugal
Eds.: Oktay Ural, Vítor Abrantes, António Tadeu
Building façades maintenance support system
Inês Flores Colen and Jorge de Brito
Department of Civil Engineering & Architecture
Instituto Superior Técnico, Lisboa, Portugal
e-mail: jb@civil.ist.utl.pt
Key words: façades, pathology, service life, proactive maintenance; costs
Abstract
This paper exemplifies the relevant aspects for the implementation of an adequate maintenance of
façade coatings with a proactive perspective. Several modules that include technological (coatings
pathology, preventive and corrective actions, inspection methods, urgent situation procedures, service
life values) and economic (application, maintenance and replacement costs) aspects are characterized.
1 Introduction
Buildings must be regarded as investments and, as such, managed in technical, economic and social
terms during their service life. In the last decades in Portugal not only has the older buildings
conservation level been aggravated jeopardizing people and goods safety but also the more recent
buildings are undergoing precocious ageing. The underestimation of the aspects related with
maintenance, through the existence of inadequate policies of renting / rehabilitation and a generalist
legislation quite often unfulfilled, has contributed to this trend.
In the case of the façades, they strongly contribute to the quality of the urban surroundings, since they
are the visible part of the buildings and in intimate connection with the environment. A degraded
façade is not only the source of non-functionality problems within the dwelling due mostly to water
infiltrations but also leads to social phenomena concerning self-marginalized population. For these
reasons, the importance that maintenance should assume and the consciousness of the reduced fraction
of the construction costs spent in that area become obvious.
The average value of 4% of the maintenance / rehabilitation sector as compared with the whole of the
construction related activities is very far from the EU average of around 35% (Euroconstruct - 1997
data). Therefore it is urgent the implementation of measures leading to a change in this trend and the
establishment of national databases about all the relevant aspects, both technical and economic, that
allow the access to specialized technical information necessary to on time maintenance practice. In
parallel, the sensitisation of every intervenient in the building process (owner, financer, designers,
builder, users, condominium management company, maintenance company) is also urgent.

Inês Flores Colen, Jorge de Brito
2 Proactive and reactive maintenance
Maintenance measures are the technical and economic actions that try to raise the quality level of a
construction element and/or restore the initial performance level, in accordance with a certain
requirement. These actions are performed in order to anticipate the elements failure or to locally
correct the existing defects, being referred to as proactive and reactive maintenance respectively.
Reactive maintenance is associated with the correction of unexpected anomalies and has almost always
an urgent character, leading to unavoidable extra costs. In this sense, it is important to standardize
technical procedures that allow the minimization of the inconveniences of this type of maintenance.
The reliability of any maintenance strategy depends on the implementation of a proactive maintenance
that acts before problems occur thus minimizing the costs throughout the buildings service life.
Proactive maintenance is of three types: preventive, predictive and improvement. Preventive
maintenance aims at planning the maintenance actions, reduces non-planned works and allows the
estimation of global costs. Predictive (or conditioned) maintenance performs inspections planning,
exhibits greater capacity of reducing unexpected anomalies and is in practice better to implement than
the previous one. Improvement maintenance is focused on the replacement of existing elements with
others with better characteristics for certain service conditions. All these types of maintenance have
disadvantages such as the need of valid supporting data at the design stage (preventive), a valid
diagnosis method (predictive) and knowledge of the behaviour of new materials (improvement).
3 Façades maintenance support system
3.1 General remarks
For proactive maintenance to be viable all data must be systemized through a technical support to back
façades inspection and maintenance management, comprising several modules associated with
different strategies. The modular character allows the addition in the future of supplementary modules
that define service behaviour of each element, contributing to the characterization of the global
behaviour of the building itself. This technical support has the following objectives: to build
supporting data with valid and consistent information about the elements behaviour and technical-
economic characteristics of the various maintenance operations; to register all the anomalies and
operations performed, making up the building’s history; to systemize procedures according to the
strategy and shape of the maintenance and to handle and update the basic data, thus continuously and
in a sustainable way improving the maintenance strategies.
3.2 Elementary modules
Based on a common methodology of the various maintenance types, the supporting system modules to
façades maintenance as proposed in this paper are characterized in the next sub-chapters.
3.2.1 Module 1 - Objectives
When defining the objectives for each building element, the role of the building owner is important to
take into account the economic and social context, in a global cost perspective (design solutions with
lower initial cost may correspond to higher maintenance costs and therefore to a higher global cost).
These solutions must fulfil the requirements of the façades coatings, such as protection of the wall
background from the aggressive elements action, watertightness of the wall, verticality and regularity
of the wall, aesthetics and cleaning ability, associated to certain levels of performance / quality.

XXX IAHS, September 9-12, 2002, Coimbra, Portugal
The decision concerning the technical solutions should search for the better compromise option, such
as the one that respects the minimum requirements while minimizing the costs. The minimum
acceptable performance of the coating, designated by minimum level of quality, corresponds in practice
to a characteristic degradation state, for example render with excessive cracking that does not protect
the background anymore. In the examples presented in this paper a minimum acceptable performance
level of 20% is admitted as the degradation state below which the ruin of the coating is reached.
3.2.2 Module 2 - Technical options
The adequate choice of the solutions depends on the evaluation of parameters related with durability,
functionality, costs involved, accessibilities and safety conditions. At this stage the existence of a
flexible design may avoid certain future situations of functional, economic, social and technological
obsolescence. In this context, the preparation of technical documents accessible to the designers,
including the procedures to be adopted and the design techniques that allow the prediction of the
elements behaviour within an adequate and timely maintenance perspective, is urgent.
3.2.3 Module 3 - Technological fundaments
The importance of characterizing the coatings behaviour leads to various complementary studies,
including laboratory ageing tests and real models testing. The sophistication of the products and its
introduction in the market lead to an increasing growth and development of the commercial activity at
the sacrifice of adequate specifications and the normalization itself. It is the makers and suppliers
responsibility to consolidate the product’s performance, through its constant correction / reformulation
and data collection from the users about the service behaviour.
Presently, technical information is very widespread and underdeveloped, making its collection and
systemization an important step. In this paper the following technological fundaments applicable to
façades coatings and in need of development in Portugal are identified: coatings service life; minimum
levels of quality; performance degradation models; coatings pathology.
The definition of the elements service life is important to the reliability of any maintenance strategy.
Its prediction can be done using the factor-method of the “Japanese Code” [1], based on the physical
degradation of the elements, depending on several factors related to: elements performance (factor A),
design level (factor B), work execution level (factor C), site and environmental conditions (factor D),
building conditions (factor E), maintenance level (factor M) and standard service life (factor Ys). The
quantification of these factors allows the estimation of the façades coatings service life, by assuming
values for standard conditions with the exception in this paper of factor M (figure 1).
0 5 10 15 20 25 30 35
Service life (years)
Monomass render
Elastic membrane
Plastic paint
Ceramic tiles
Natural stone
Service life values for M=0.8
Figure 1: Service life values for inexistent or inadequate maintenance [2]
The definition of the degradation models depends on an adequate methodology of diagnosis of the

Inês Flores Colen, Jorge de Brito
degradation mechanisms, based on the knowledge of the relevant anomalies and of the exterior agents
and on the evaluation of the causes. When adjusted, these models allow the preparation of an
economic long-term planning and the estimation of the element’s residual service life. Presently there
are no degradation models sufficiently calibrated to warrant an easy application, therefore needing
careful investigation. Some of the models studied are exemplified in further modules (8, 9 and 10).
Table 1 presents some of the current anomalies in the façades coatings under study and their causes.
3.2.4 Module 4 - Maintenance operations
Each maintenance strategy may include several operations such as cleaning, inspections and repairs /
local replacements. The cleaning operations, almost always underestimated and frequently neglected,
are most relevant in the prevention of other anomalies, namely in the evolution of stains and
accumulation of other deposits in the coating surface. The inspection operations should have their own
methodology and be sustained by adequate diagnosis techniques about the state of each coating
(finishing condition, cleanness, background adherence, cracks, etc.). The repair / local replacement
operations aim at solving certain anomalies that manifest themselves in localized areas in order to
prevent its propagation to the remaining façade coating. These operations should be performed after
the analysis and the correction of the anomalies causes, adopting techniques adequate to each type in
order to avoid the appearance of “repathology” phenomena. Table 2 presents some of the correction
and prevention techniques associated with the anomaly types of Table 1.
3.2.5 Module 5 - Planning
Planning differs in preventive and predictive strategies. In the first one the maintenance actions are
planned taking into account the recommended periods. In the second one only the coatings inspections
are planned. The establishment of a periodicity of the maintenance actions allows the rationalization of
any strategy, by relating the intervention type, the quality level demanded and the degree and type of
plain deterioration. The legal period of 8 years established by RGEU / D.L. No. 177/2001 (New
Juridical Regime of Urbanization and Edification) for the maintenance of current buildings is not
always fulfilled and in some cases it is even inadequate. On the other hand, an excessive reduction in
Table 1: Coatings anomalies and possible causes [3]
Cracking
- initial drying shrinkage
- application carelessness
- differential dimensional variations between materials
- background cracking
- ageing due to ultraviolet exposition
- building specifications absence
Swelling and Loss of adherence with scaling
- coating bad quality
- application on inadequate or badly prepared background
- insufficient water permeability of the coating
- inefficient setting / sealing
- frequent water penetration
- fracture of the metallic fastening elements
Aspect degradation
- stains (efflorescence, funguses, moulds, dirt)
- differences of shade
- insufficiently sun exposed façades subject to frequent humidification
- dirt accumulated in the surfaces
- humidity caused stains
- degraded joints sealant material

XXX IAHS, September 9-12, 2002, Coimbra, Portugal
the periodicity of the maintenance operations may generate unnecessary expenses.
Concerning the inspections periodicity, three fundamentals periods must be taken into account:
• initial period - inspection between 2 and 5 years after construction, in order to evaluate the pre-
pathology phenomena and possible youth anomalies;
• final period - inspection in the 2 to 5 final years of each cycle, in order to evaluate the tendency
to achieve / overtake the minimum level of quality (“imminent ruin”);
• intermediate period between the previous ones that corresponds to periodic inspections before (1
to 2 years) interventions, in order to evaluate the expected behaviour and detect possible
phenomena of “repathology”, resulting from previous deficient repairs.
Table 2: Maintenance operations techniques [3]
Cleaning techniques
- manual scouring and scrubbing to remove the degraded coating
- simple pressure water jet or neutral liquid detergent
- scabbling down to the background surface
- dry scrubbing of whitish stains
- aqueous disinfectant application
Inspection techniques
- visual observation of the accessible areas
- sounding by tapering over non-adherent patches
- boroscopy
- mortar petrographic analysis
- in situ measurement of coatings depth
- ultra-sounds
- termography
Repair / local replacement techniques
- application of synthetic coating in fine cracks
- widening and filling of average cracks with adequate material
- resins injection in cracks of broken elements with crack filling
- broken elements removal
- replacement with epoxy and stone dust based special mortars
3.2.6 Module 6 - Costs
To estimate the global cost of the option for each maintenance strategy, it is important to estimate the
various types of cost (application, maintenance and replacement), taking into account the techniques
(module 4). Table 3 presents the costs used in the comparison of the various strategies under study.
3.2.7 Module 7 - Economic tools
The decision about the best maintenance strategy must take into account all the relevant aspects, even
the most subjective, by resorting to decision support economic tools, adapted to each type of analysis.
In this study, the LCC (life cycle cost) method was used. It allows the comparison of costs between
several strategies with different service lives, backing the decision of the choice of the most favourable
strategy from the cost-efficiency point of view, the one with the lowest VAE LCC (annuity), and
therefore minimizing the global cost throughout the total building service life.
In the next modules the three types of proactive maintenance strategies are applied to five façades
coatings, taking into account the information already collected in the previous modules (1 to 7).
3.2.8 Module 8 - Preventive maintenance
Maintenance strategies
• Strategy 0 - no maintenance (model I - Table 4);

Inês Flores Colen, Jorge de Brito
• Strategy 1 - periodic cleanings (model II);
• Strategy 2 - periodical light repairs (model III - Table 4);
• Strategy 3 - one heavy repair (model IV).
Table 3: Application, maintenance and replacement costs [3]
Application costs
- monomass render (15,46 €/m2)
- non-reinforced elastic membrane coating (8,98 €/m2)
- texture plastic paint coating (7,48 €/m2)
- ceramic tiles applied with adhesive mortar, including closing of cracks (22,45 €/m2)
- cramped and cement glued natural stone (55,77 €/m
2
)
Maintenance costs
- visual inspection of degradation condition (0,50 €/m2)
- scrubbing and water jet cleaning (1,00 €/m2)
- cracks treatment (10,97 €/m2)
- widening and closing of superficial non-structural cracking with non-retractile mortar (13,47
€/m2)
- scabbling of existing render (7,73 €/m2)
- cracks treatment in ceramic tiles (4,99 €/m2)
- repair / replacement of broken ceramic tiles (27, 43 €/m2)
- joints treatment in natural stone (6,98 €/m2)
- repair / replacement of broken stones and cramps (72, 33 €/m
2
)
Replacement costs
- scabbling of existing render (7,73 €/m2)
- cleaning and preparation works of degraded surfaces (1,00 €/m2)
-
removal of debris and scabbling of the existing ceramic tiles, including surface
regularization (5,49 €/m2)
- removal of existing stones and surface regularization (16,56 €/m
2
)
Table 4 - Examples of degradation models (I and III) (monomass render) [3]
Characterization:
The model I initial degradation curve corresponds to a second or higher degree polynomial expression
with a degradation rate that slowly increases from the beginning (≅4,5%) until the end (≅8,0%) of the
service life of 13,5 years for a minimum quality level of 20%. In model III the periodic repairs alter the
initial shape of the curve, increasing the performance level of the coating after each operation. After
eight light repairs with a period of 1/3 of the service live of model I, a new service live of 40 years
(about three times the initially predicted) is reached. Models II and IV were also developed in [3].
3.2.9 Module 9 - Predictive maintenance
Maintenance strategies

XXX IAHS, September 9-12, 2002, Coimbra, Portugal
• Strategy 0 - no maintenance (predictive model I - Table 5);
• Strategy 2 - periodic light repairs (predictive model II - Table 5);
• Strategy 3 - one heavy repair (predictive model III).
Table 5 - Examples of degradation models (predictive I and II) (monomass render) [3]
Characterization:
The definition of a predictive strategy is based on the average behaviour expected of the material in
real conditions (curve Tm), while a preventive strategy relies on a theoretical pessimistic prediction
(curve Tk
). So in average it is expectable that by resorting to periodic inspections it is possible to find
out that the real behaviour of the coatings is in fact slightly better than the one admitted in a preventive
strategy. In these models it was assumed that right after the 1st inspection it was detected that the real
degradation rate of the coating’s performance was 20% lower than the one assumed in the preventive
strategies and that this trend was consistent afterwards, thus leading to a new reality in terms of the
periodicity both of the interventions and the inspections. Predictive model III was also developed in [3].
3.2.10 Module 10 - Improvement maintenance
Maintenance strategies
• Strategy A - repair the existing coating with a material with similar characteristics in terms of
degradation rate, with a periodicity equal to 1/3 of the initially predicted service life, whose
value decreases 20%;
• Strategy B - replace the existing coating with another with better characteristics in terms of the
local conditions; three improvement models were analysed, admitting the most economic
preventive strategies for each type of coating:
a) Monomass render → natural stone (improvement model I);
b) Plastic paint → elastic membrane (improvement model II - Table 6);
c) Ceramic tiles → natural stone (improvement model III).
3.3 Analysis of the results
From the results obtained for the various strategies in [3], it was concluded that:
• in the preventive strategies, the most economical for the scenarios analysed were light repairs
for the monomass render and the elastic membrane (less “noble” coatings), absence of
maintenance for the plastic paint (short service life) and one heavy repair for the ceramic tiles
and the natural stones (“nobler” and more expensive coatings);
• a predictive strategy is usually more economic than a preventive one, since it evaluates the
material’s average behaviour contrary to in the preventive strategy (necessarily conservative);
therefore, it is particularly adequate for coatings of non-traditional materials, for which the

Inês Flores Colen, Jorge de Brito
existing lack of experience advices a more conservative attitude in the preventive strategies;
• an improvement strategy may contribute to a reduction in the obsolescence of certain coatings;
this strategy usually increases the technical level of the coating, even though it is costlier; the
replacement of plastic paint by an elastic membrane has proved to be a favourable improvement
technique from the cost-efficiency point of view; these replacement cost could be avoided if the
membrane were the design option for service conditions subject to high cracking risks.
Table 6 - Example of degradation model (improvement II) (monomass render) [3]
Characterization:
The definition of an improvement strategy is based
on an accidental real behaviour of the coating
associated with higher values of degradation rate than those predicted for the preventive strategy. This
situation occurs in practice when a coating does not clearly fulfil the pre-established requirements or
when gross coating design mistakes are detected. In these models it was assumed that right after the 1st
inspection it was detected that the real degradation rate of the coating’s performance was 20% higher than
the one assumed in the preventive strategies, and therefore the replacement with another coating was
analysed. Improvement models I and III were also developed in [3].
4 Conclusions
The choice of a maintenance strategy must take into account the specific coating under analysis: its
service behaviour (anomaly types, degradation models, service life), the costs involved and corrective /
preventive techniques, in order to give the decision-maker information as complete as possible in the
estimation of real characteristics scenarios. To develop a technical support system for programmed
maintenance management, all the previous parameters must be included in a database and be
optimised and monitored through inspections and records during the building service life. An adequate
information system can decisively contribute to a growing improvement of the area’s state of the art.
References
[1] The English Edition of Principal Guide for Service Life Planning of Buildings, commented edition,
Architectural Institute of Japan, 1993, 98 p.
[2] Flores Colen, I.; Brito J. - Vertical Envelope Maintenance - Application of Preventive Strategies
(Part I) (in Portuguese), Journal Arquitectura e Vida, No. 27, V. II, May 2002, pp. 90-95.
[3] Flores, I.; Maintenance Strategies - Current Buildings Envelope Elements (in Portuguese),
Masters Thesis, IST, February 2002, 186p.