Lisø PhD Dissertation Manuscript - NTNU

screen in a two-stage weatherproofing. It will also act as a mechanical safeguard for any
underlying barrier layer, e.g. roofing. The flashing and underlying structure must always be
designed so that any possible water entering behind the flashing will not penetrate the
structure behind.
3.9. New rendering recommendations
A three-coat rendering system has to be used to resist heavy driving rain conditions,
frequently experienced along most of the extended Norwegian coastline. A two-coat render
is not sufficient [17]. The empirical material investigated here confirms this conclusion.
The final coat in a three-coat render may be a suitable inorganic coat like silicate paint.
Insufficient and inaccurate performance guidelines on how to ensure satisfactory rain
protection and how to avoid cracking has always been a problem, and design
recommendations need to be further developed to ensure local-level climate adaptation.
4. Conclusions
When correctly designed and constructed, and with due consideration paid to the
distinctive features of masonry, few other materials can match its durability characteristics.
However, the level of learning amongst the different actors in the construction industry
involved in the design and performance of masonry structures varies greatly. Moisture
related masonry defects clearly dominate the picture in Norway, largely due to a lack of
both understanding and attention in the designing and carrying out of masonry buildings.
The large number of simple and recurring defects presented supports the need for a more
thorough understanding of fundamentals of masonry structures and building physics. It is
also important to facilitate the exchange of knowledge across borders in relation to national
distinctive climates and consequences of building defects under different climatic impact.
This is of particular importance due to an ever-increasing internationalisation and
exchange of labour. Country distinctive or local knowledge is also necessary when
developing nationally adapted product documentation in the form of technical approval
and certification.
The presented types of defects and causes indicate a need for both new knowledge,
and new methods to ensure the employment of existing knowledge. The described defects
at His Majesty the King’s Guard Huseby Barracks could have been avoided if the existing
Building Regulations and Codes of Practice had been adhered to, and if the carrying out of
the project had been more thoroughly supervised. Experience gained from the recently
completed rehabilitation represents a valuable example for future learning.
Driving rain and frost action are the principal climatic challenges to be considered
in the pursuit of high-performance masonry structures in severe climates. Shrinkage and
thermal movement, the most frequent defect category in this investigation, dominate
independent of the climatic impact. It is a defect category more dependent on the design
and construction of masonry structures. First-class workmanship necessitates a correct
moisture level in the blocks when bricked in, and movement joints and the sliding layer
(damp proof course) being carefully considered throughout the construction process.
The investigation also discloses the fact that merely small errors or mistakes can
bring about major and often irreparable defects or damage to masonry structures. A large
part of the investigated cases could have been avoided through more detailed engineering
and applied knowledge on existing design guidelines. The investigation finally reveals the
need for design guidelines to ensure local climate adaptation, and improved design
guidelines on movement joints.
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