Moisture dynamics in the masonry fabric of historic buildings subjected to wind-driven rain and flooding

Current climatic projections show clearly that increasingly more extreme weather events are to be expected in the future. Historic buildings are considered to be the most vulnerable to this adverse climatic impact, via moisture induced deterioration and resulting strength decay in their construction materials. Therefore, the identification of these climatic effects is important to be able to develop suitable tools to mitigate them, both for individual buildings and on a regional scale. This paper presents the analysis of a comprehensive environmental monitoring of two historic buildings in Tewkesbury, Gloucestershire, UK, to provide thorough insight on their performances under environmental loading on a comparative basis. Firstly, the effect of wind-driven rain (WDR) and flooding is assessed by correlation with relative humidity (RH) measurements. The WDR measurements are then compared against values calculated using well established semi-empirical models and reasons behind the limited correlation are discussed. The dynamic hygrothermal response of two different historic fabrics is studied in greater detail by monitoring in-wall temperature and RH. The conclusions drawn from the analysis of the monitoring outputs are then further elaborated on by using hygrothermal characterization obtained by dynamic vapour sorption (DVS) testing of material samples extracted from the fabric of these buildings. The study concludes that the current environmental conditions pose a threat on the building envelopes unless routine maintenance is provided, and that monitoring methodology devised is clearly successful in quantifying the exposure of the two historic buildings to environmental conditions, onsetting deterioration phenomena in the envelop materials

Seismic performance evaluation of traditional timber hımış frames: capacity spectrum method based assessment

Timber constructions have been widely suggested to be seismically resistant based on post-disaster reconnaissance studies. This observation has, however, remained to a large extent anecdotal due to the lack of experimental work supporting it, especially for certain timber architectural forms, including traditional timber frame “hımış” structures. To fill this gap, the authors carried out an extensive full-scale testing scheme using frames of various geometrical configurations, tested under reverse-cyclic lateral loading with/without infill (brick and adobe) or cladding (bağdadi and şamdolma) (Aktas et al. in Earthq Spectra 30(4):1711–1732, 2014a, b). The tests concluded that hımış frames had high energy dissipation capabilities due mostly to nailed connections. Infill/cladding significantly helped improve stiffness and lateral load strength of the frames, and timber type did not seem to make a remarkable impact on the overall behaviour. The current paper, on the other hand, uses test data to calculate capacity/demand ratios based on capacity spectrum method and Eurocode 8 to elaborate more on the performance of “hımış” structures under seismic loading. The obtained results are discussed to draw important conclusions with regards to how frame geometry and infill/cladding techniques affect the overall performance

Indoor Mould Testing of a Historic University Building: UCL Chadwick Building

Indoor mould is one of the most important determinants of indoor air quality, with serious implications not only on human health, but also on the building envelope itself. This study is based on the Chadwick building, which is a late 19th century building, currently under the ownership of UCL as a workplace and school. Therefore it brings together different functions which are conventionally discussed separately in the relevant literature. This study aims to measure airborne and surface mould concentrations within the Chadwick Building, and to find out the correlations between these and the physical characteristics of the tested spaces. To this end, 3 classrooms, 3 offices, 3 laboratories, and 1 activity room were sampled to examine the airborne (active or aggressive) and surface mould concentrations. Samples were analysed for the β-N-acetylhexosaminidase (NAHA) activity to determine the fungal cell biomass at the laboratories of Mycometer in Denmark. The testing protocol also involved active particle counting, and temperature and relative humidity measurements. Offices were found to be the least mould intensive spaces, while laboratories were found to have the highest level of mould and particle intensity among all tested spaces. Based on the benchmarks previously established for residential indoor environments (currently in use by the Danish Building Institute), the results showed that most of the tested spaces did not have no mould and with a good/normal cleaning standard. Only one space and a few surfaces indicated either a minor (most likely non-building-related) mould, or a poor cleaning standard. The validity of these categories for a workplace/school should be further investigated by future research

Moisture content as a deteriorating factor for common building stones in London

Moisture content and its distribution within the rock mass can affect its deterioration. This has not been considered in details in the context of their specific properties for the common building stones in London such as limestone, granite and marble. Based on an extensive literature survey on specific rock properties and observed surficial deterioration from this study, it is evident that deterioration can be correlated to moisture transport and retention. For example in limestone, it can be related to their sorption-behaviour in response to subtle changes in humidity, intrinsically controlled by their porosity and pore structure. In marble, surficial moisture condensation enhances deposition of airborne particles accelerating chemical and biological decay, influenced by grain size and interlocking

Assessment of flood and wind driven rain impact on mechanical properties of historic brick masonry

As a result of increased rainfall and flooding the building fabric of historic structures in exposed areas are likely to be subject to higher and more sustained moisture content levels, along with experiencing an increased frequency and severity of wetting and drying cycles. This study aims to evaluate the impact of such cyclic wetting and drying on the mechanical behaviour of historic brick masonry. The reported results are obtained from a series of weathering and mechanical tests carried out on clay bricks and masonry specimens. The weathering test regime derives from analysis of observed weather data, combined with review of similar existing test protocols. Similarly, a modified mechanical test procedure is applied to simulate fatigue observed in the field. The results indicate that exposure to the weathering tests results in a reduction of masonry shear strength. This is discussed within the context of wider work carried out at a case study location, and highlights the value of designing a weathering regime that can more closely replicate the in-situ weathering processes. In this way the data collected in this experimental programme is shown to be suitable for use in contextual analysis of individual historic masonry case studies, with respect to climate change and the associated alteration of wetting regimes

Associations between home characteristics and mould levels in UK

Mould growth is governed by a complex set of factors, including among others physical characteristics of a given indoor environment, as well as how that space is used, i.e. heating, cleaning and ventilation habits, however how and to what extent these define propensity to grow mould is unclear. This study uses data from a testing scheme on 84 rooms in 18 properties to shed further light on these questions through elastic net regression analysis. The testing data includes the air and surface mould readings quantified based on the activity of β-N-acetylhexosaminidase (EC 3.2.1.52; NAHA), and particle intensity in each room

The effect of the airflow pattern inside air gaps on the assessment of interstitial mould: A theoretical approach

Internal wall insulation is one of the few, possibly, the only feasible solution to efficiently reduce heat losses through the external walls of buildings where the application of external insulation is not an option, for example, in conservation areas. However, the application of this intervention may lead to unintended consequences, such as moisture accumulation and mould growth. Currently, no international standards and regulations exist to evaluate these hazards via non-destructive inspections. Air sampling through impaction and culture-based analysis was suggested in previous research as a potential non-disruptive methodology for interstitial mould testing. The method requires the perforation of the inner side of a wall and the creation of airflow through the operation of a pump, to allow the collection of particles from the confined space of interest. The present study aimed to assess the location of perforations and their effect on the airflow created and the airflow pattern variations due to changes in the airflow velocity at the outlet. Results regarding airflow features such as the turbulence intensity, dynamic pressure and volume-averaged velocity were also extracted and discussed. Practical application : The rapid changes in climate and net-zero emissions targets call for major improvements of the existing building stock towards a more sustainable future. The installation of internal wall insulation is one of the few and might be the only feasible solution for the efficient reduction of heat losses through uninsulated walls. However, this intervention might lead to moisture accumulation and thus moisture-related problems such as mould growth. This study aims to build upon previous work on interstitial mould growth assessment and contribute to the development of a well-defined testing protocol for building professionals

Performance Comparison of Surface Waterproofing Products with Various Chemical Compositions on Brick Masonry

Moisture risk in building systems is one of the major concerns affecting the durability of building envelopes and indoor comfort. Surface waterproofing products are a common and simple methods to enhance the moisture performance of masonry buildings. However, the various chemical compositions of these products can lead to very different performance under exposure. This paper focus on the comparison and discussion of the different level of impact of surface waterproofing products with various chemical compositions on the performance of brick masonry substrate through a series of benchtests on small scale specimens to test water vapour transmission, hydrophobicity and liquid water absorption. Four different types of waterproofing products were selected, along with 3 brick types common in the 50s and 60s to be representative of the majority of the UK building stock. Results show that the combined outcome of the three tests is sufficient to identify the clearly the effectiveness of the products in improving waterproofing while ensuring vapour transmission. It also shows that it is essential to use specimens reproducing the masonry fabric rather than samples of the individual materials

Wind Driven Rain (WDR) Laboratory Tests on Cavity Wall Specimens treated with surface waterproofing products

Wind driven rain (WDR) is one of the most common sources of moisture risks affecting buildings in the UK. Water penetration can lead to defects such as ineffective insulation, damp inner walls and freeze-thaw damage, causing issues in both energy efficiency and wall integrity. Surface waterproofing products have shown great potential as a new method of improving the moisture condition in buildings. This paper is focused on real size cavity walls tested under WDR exposure to study the hygrothermal performance of surface waterproofing products. Test results show both acrylic-based liquid and silane/siloxane blend cream products were capable of lessening moisture enrichment of masonry cavity walls under cyclic WDR loading

Air sampling and analysis of indoor fungi : a critical review of passive (non- activated) and active (activated) sampling

For over a century, researchers have been concerned with what testing protocols to assess indoor fungi growth were most reliable. To that end, various sampling and analysis methods were developed. However, to present no testing procedure has been standardised. The vast number of different fungi species, the differences in their biological properties and their implications on the occupants’health and building fabric can make the decision-making process for an appropriate assessment protocol challenging. This research aims to make a critical review of passive (or nonactivated) and active (or activated) sampling and emphasize potential errors while interpreting results obtained from passive or active protocols