Lisø PhD Dissertation Manuscript - NTNU

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NDEA has therefore chosen to replace all brickwork in façades and to replace wall/roof connections, including new roof overhangs, gutters and drainpipes. Replacement of roofing tiles on a large part of the roofs and reconstruction of all wetrooms along with the removal of mould growth and efflorescence of salts also forms part of the refurbishment. Fig. 4. His Majesty the King’s Guard Huseby Barracks, Oslo, Norway. Source: Norwegian Defence Estates Agency (NDEA). The expensive, extensive and necessary refurbishment described is meant to ensure a new military facility with long lifetime. The project was carried out at a cost of about 40 million Euros (the project being completed in 1985, the cost given in 1985 equivalent). The rehabilitation costs, completed in 2005, amount to more than 17 million Euros (2005 equivalent). The described defects could have been avoided in the first place if the existing Building Regulations and Codes of Practice had been adhered to, and if construction of the project had been more thoroughly supervised by the NDEA. 3. Towards new climate adapted design guidelines 3.1. Introduction The investigation of two decades of process induced masonry defect assignments shows that it is possible to obtain durable masonry structures even in countries like Norway, with harsh and extremely varied climatic conditions. However, there is a great potential for both improved design and workmanship. The analyses also reveal that the most frequent types of damage and defect surveyed are rather easy to avoid, simply by applying existing knowledge and by being more aware of the local climatic features and trends on the actual site. Masonry defects can be understood as a function of local climatic impact, choice of materials and matching composition of materials, design and quality of workmanship. The pursuit of durable masonry structures requires an optimal realization of both the climatic exposure and the special features of brickwork. Masonry structures are “maintenance-free” only if properly planned, designed and constructed. Well-functioning methods and solutions for a typical inland climate (weather-protected areas) are not necessarily Page 8 of 12
appropriate in a more severe type of climate. The presented lessons learned are highly relevant also for geographical areas other than Norway, e.g. the most exposed parts of the UK, and is a first approach towards improved design guidelines for masonry structures in harsh climates. 3.2. The two-stage tightening principle The results clearly illustrate that the employment of the two-stage tightening principle (i.e. separate wind and rain barrier) is crucial in climates with severe driving rain exposure. This is in agreement with the recommendations of Stirling [8]. However, there is a wellestablished tradition in several European countries with fully filled cavity. Hens et al. [9] suggests that such walls, even with open head joints, can maintain a satisfactory rain protection, dependent on the severity of climatic impact and the combination of materials used. Yet, there exist no distinct guidelines for when and where to use fully filled cavity walls. The development of such guidelines may be based on the methodologies given in BS 5628-3:2001 [10], which do not advise full cavity fill of unprotected masonry on the west coast of Scotland, parts of North West England, much of Wales, and South West England, due to driving rain exposure (according to assessment methods given in BS 8104:1992 [11]). The investigation indicates that one weephole per meter is sufficient to drain water from cavity trays at the lower edge of cavity and veneer walls in climates with sheltered or moderate driving rain exposure. There should be two weepholes per meter where severe driving rain exposure is expected. 3.3. Position of window The correct positioning of windows in cavity and veneer walls is important to avoid defects. Windows should be installed parallel to, or flush with, the thermal insulation layer to avoid thermal bridges and subsequent heat loss. As a main rule the turn-up at the rear edge of the weatherboard flashing should rest directly against the cold side of thermal insulation layer. This positioning of the window ensures a low heat loss, a robust rain protection (especially important in climates with high driving rain impact) and a low risk of moisture defects. The window can be positioned further to the warm side of the wall in cold inland areas with a low driving rain impact, in order to reduce the risk of internal condensation problems. But, in these cases the tightening details around the window must be carefully considered. 3.4. Frost resistance The frost resistance of masonry depends on a complex set of material properties and on the climatic impact on the material, e.g. [12]. In part due to this complexity frost resistance of brick and rendering mortar is still tested according to rather simple methods given in different international and national standards. There are designated test methods for different countries, but the results presented in this investigation shows that the performance of masonry depends on climatic exposure at the very local level. Annex B of NS-EN 771-1:2003 [13] includes exposure examples for masonry or masonry elements dependent on the design of the construction, i.e. the risk of frost decay in a given climate. However, the climatic conditions are not specified in the standard. Simple climate adapted design recommendations for the use of bricks in the United Kingdom is provided by Hanson Brick [14]. However, a more pronounced relationship between frost resistance and Page 9 of 12
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Building envelope performance asses
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Lisø, K.R./ Building envelope perf
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BUILDING RESEARCH &INFORMATION (200
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LisÖ et al. on how to cope with an
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LisÖ et al. the exposure to contin
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LisÖ et al. business premises. The
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LisÖ et al. construction industry
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Research in Building Physics, Carme
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4 CLIMATE CHANGE SCENARIOS FOR NORW
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with large amounts of precipitation
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will most likely be worse, even wit
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Graves, H.M. & Phillipson, M.C. 200
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766 Nordvik and Lisø The topic of
Page 64 and 65: 768 Nordvik and Lisø into the futu
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Page 73 and 74: BUILDING RESEARCH &INFORMATION (200
Page 75 and 76: cost of repairing process-induced b
Page 77 and 78: change in quality (Mehus et al., 20
Page 79 and 80: on the impacts of different climati
Page 81 and 82: different strategies: risk-based, p
Page 83 and 84: Lisø, K.R./ Building envelope perf
Page 85 and 86: Learning from experience - an analy
Page 87 and 88: An important aspect of the programm
Page 89 and 90: Concrete walls 32 % LECA masonry 10
Page 91 and 92: construction industry, and academic
Page 93 and 94: BUILDING RESEARCH &INFORMATION (JAN
Page 95 and 96: greater variations (Lisø et al., 2
Page 97 and 98: Typical problem areas and recommend
Page 99 and 100: Figure 3b Recommended design of win
Page 101 and 102: Figure 7 Example showing the recomm
Page 103 and 104: Figure 11a Poor solution for a £as
Page 105 and 106: Acknowledgements This paper was wri
Page 107 and 108: Climate adapted design of masonry s
Page 109 and 110: 2. Masonry defects in Norway 2.1. S
Page 111 and 112: Fig. 2. Example illustrations of th
Page 113: The presented results are in good a
Page 117 and 118: screen in a two-stage weatherproofi
Page 119 and 120: INCREASED SNOW LOADS AND WIND ACTIO
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Page 125 and 126: The number of buildings investigate
Page 127 and 128: As is apparent from the values in t
Page 129 and 130: climate change is now dominated by
Page 131: TABLE 3. Summary of findings Struct
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Page 136 and 137: temperature of -4°C or less. See F
Page 138 and 139: Today, frost resistance of brick, c
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Page 144 and 145: A possible objection to the present
Page 146 and 147: [17] Dührkop H., Saretok V., Sneck
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Page 155: Acknowledgements This paper has bee
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Page 160 and 161: Fig. 1. Map of Norwayshowing the lo
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interesting to compare those result
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Effects of wind exposure on roof sn
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In ISO 4355 ”Bases for design of
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variety of roofs and wind exposures
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Li and Pomeroy [13] evaluated hourl
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Fig. 5. Exposure coefficients for 3
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meteorological stations are expecte
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Many of the meteorological stations
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the ground with return period of 30
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References [1] Standards Norway. De
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