Exterior Cladding Research Articles

Service life prediction of exterior cladding components under standard conditions

An empirical method was developed for the prediction of the service life of building components, based on an evaluation of their actual performance and on the identification of failure mechanisms affecting their durability. The service life of exterior components subjected to normal service conditions is predicted. Four types of exterior claddings are exemplified: cementitious mortar, synthetic rendering, ceramic mosaic, and wet‐fixing stone cladding. The proposed prediction models yield high degrees of fit to the data (R 2 in the range of 0.86 to 0.93 at a 0.0001 level of significance). Life cycle costs (LCC) analysis – following service‐life prediction results – leads to the conclusion that maintenance and replacements costs account for 10–80% of initial capital costs. Synthetic rendering exhibited the highest LCC effectiveness, reflecting durability and low capital costs. The method can be used for planning preventive maintenance, evaluating economic implications of failures, and planning service life.

Characterizing close fitting enclosures for fluid-loaded cylindrical sources

The influence of a close fitting enclosure on the radiated noise from a submerged (in water) acoustic source has been shown to be beyond the scope of simple close fitting enclosure expressions found in some textbooks, especially when dealing with relatively soft intermediate layers [Cuschieri, J . Acoust. Soc. Am. 115, 2537 (2004)]. A more detailed analysis is thus warranted. Using a multilayer shell approach, with the innermost layer representing the source with uniform radial velocity, the middle layer representing the intermediate isolation layer and the outside layer representing the exterior cladding, with water fluid-loading on the outside of the exterior cladding, the insertion loss (IL) of the multiple layers is investigated for different intermediate layer materials, different exterior cladding layer characteristics and source size. IL results are presented as a function of frequency and layer/cladding characteristics. From the formulation the behavior of the intermediate layers is also obtained which help explain the IL results. [Work sponsored by ONR.]

Issues in Construction of a Unique Heavily Reinforced Concrete Structure

The owner of a recently constructed facility described in this paper specifically required that a portion of their facility, referred to as the “concrete structure,” be constructed as a self-supporting structure. Additionally, no portion of this concrete structure could bear loads from upper building walls or floors. Structural retaining walls were required to isolate the subgrade portion of the concrete structure from lateral soil loads, while supporting loads of the exterior cladding system and roof structure. These requirements presented a unique construction challenge. The combination of a cast-in-place structural enclosure, exterior tilt-wall panels, and precast double-tee roof members provided a facility that met the owner's criteria.

Effect of Surface Temperature on Water Absorption Coefficient of Building Materials

Water absorption coefficient of a material governs the liquid moisture movement into it. In the case of various components of a building envelope, in particular exterior claddings, this is one of the most important hygrothermal material properties that needs to be assessed to determine the overall moisture management strategy. In different geographical locations, components of the building envelope, in particular the surface of the exterior cladding, are exposed to various temperature regimes. However, the effect of various temperature regimes on the water absorption coefficient of common building materials has not been adequately investigated. This study looks at the water absorption characteristic, determined through water absorption test, of three commonly used building materials (i.e., eastern white pine, red clay brick and concrete)at four temperature levels at the surface of the material, ranging from 3 to 35° C. A clear surface temperature effect on water absorption coefficient and derived liquid diffusivity value is shown in eastern white pine whereas changing the surface temperature shows no effect on the water absorption characteristic of red clay brick and concrete.

Modal Analysis of Steel-Framed Residential Structures for Application to Seismic Design

There has been a significant worldwide increase in the use of cold-formed steel in low-rise resi dential structures as an alternative to timber. A major research project to assess the performance under lateral loading of cold-formed steel frames commenced more than 7 years ago at The University of Melbourne, Australia, in collaboration with industry and other research organizations. This paper reports key findings from an extensive experimental program. It details a particular aspect of the program that uses nondestruc tive dynamic testing to identify the basic dynamic properties of such structures. Laboratory tests, employing a shaking table, have been conducted on unclad wall panels and a model test house to study the influence of different framing connection types and to assess the influence of nonstructural components, namely, plas terboard interior lining and brick-veneer exterior cladding. The findings from these tests were verified and further extended by testing a full-scale prototype house at various stages of construction. This paper presents information concerning typical natural frequencies and mode shapes for such structures. It also details the contribution of nonstructural components to the lateral stiffness, which was found to be significant. The re sults have important implications for seismic design and performance of such structures, even in regions of low to moderate seismicity.

Long‐term natural weathering of coated ThermoWood

Heat treatment reduces hygroscopicity and accompanying dimensional changes in wood. Prior to coating, pine and spruce boards were heat treated at 225°C for six hours under steam, in order to achieve dimensional stability and durability of wood substrate. The panels were coated surface finishes which are commonly used on exterior cladding, joinery and fences in Finland. Performance of the coated heat‐treated and untreated panels was monitored during five years’ outdoor exposure. Without coating the heat‐treated wood is not weather resistant. The original dark brown colour of the uncoated heat‐treated wood panels was not stable when exposed to weather, turning grey. Cracking of the heat‐treated wood without coating was at the same level as that of the untreated wood despite the lower moisture content of the heat‐treated wood. The unpigmented or low build stains and oils did not prevent cracking of the heat‐treated wood. Weather resistance of the heat‐treated wood was improved by the water‐ or solvent‐borne paints. Wood heat treated by means of this process is comparable to untreated wood as a substrate for coatings and no alterations in coating recommendations are needed when considering coating of heat‐treated wood.

Exterior Cladding Methods: A Technoeconomic Analysis

The continual development in building components and the significant increase in the proportion of high-rise building lead to an extended use of new methods of exterior cladding. The selection of a cladding system incorporates various aspects, among which the more significant are: physical and visual performance, life span of the cladding, and economic considerations. This paper focuses on the systematic examination and comparison of four different categories of cladding methods based on technological and economic criteria. The categories of claddings are: cementitious stucco, synthetic finish stucco, ceramic, and natural stone. The economic analysis, based on life-cycle cost (LCC) and on life-span estimates was arrived at by an analysis following on-site observations. It is shown that in “noncorrosive” environments, cementitious stucco is preferable to alternatives, particularly in low-rise buildings. In “corrosive” environments, synthetic and ceramic mosaic claddings are preferable to the alternatives e...

Pressure model techniques for cladding loads

The pressure model test is now used as a well accepted procedure for determining wind pressures on the exterior cladding of tall buildings. The methods used in a pressure model study are reviewed including measurement system frequency response, the determination of peak pressure coefficients, combining wind tunnel and meteorological data and evaluating internal pressures. In addition, an assessment is made of the uncertainties involved in wind tunnel testing as compared with using building code methods.

Probabilistic characterisations of durability of reinforced concrete

In assessing the durability of a concrete structure such as cladding on high-rise buildings, major concern is with estimating the cover of concrete to steel reinforcing and the depth of carbonation with a view to forecasting the proportion of activated (corrision susceptible) steel at time t and hence likely extent of future damage to building. This paper examines some of the statistical model development and analysis associated with factors initiating corrision of steel reinforcing in the context of a recent study of a high rise office building showing signs of damage to the exterior cladding. In particular, procedures for the estimation of proportion R of the building with depth of carbonation exceeding cover are proposed when a Weibull probability model is shown to characterise depth of carbonation for the structure. Confidence bounds are derived and assessed relative to alternative procedures proposed by various authors. In particular the case where R is small is examined. The procedure enables the forecasting of likely extent of future damage.

The flammability of exterior claddings

The author reports on a series of tests conducted to study the vertical flame-spread characteristics of certain exterior cladding materials. The results take into account several types of construction.

Theoretical and experimental studies on the stresses and strains in claddings of annular boiling-superheat fuel elements

The high temperature difference between exterior and interior cladding in an annular combined boiling-superheat fuel element results in considerable axial stresses and strains in both claddings during reactor operation. Each start-up or shut-down of the superheat reactor causes cyclic changes of these stresses and strains. In the first part of this report the equations necessary to predict the behaviour of boiling-superheat fuel elements are deduced and the resulting stresses and strains are given for several examples with various cladding materials. The second part of this paper reports the results of experimental studies with boiling-superheat fuel elements in an out-pile thermal cycling test facility. Full size fuel element specimens have been subjected to up to 800 severe thermal cycles. The observations made, including some defects which have occurred, are discussed. The results are critically reviewed and compared with the analysis of part one. Even considering the fact that the mechanical properties under irradiation at high temperature of the cladding materials of interest are not very well known today, it is felt that the axial stresses and strains in a boiling-superheat fuel element do not present an unsurmountable problem in the development of this type of fuel elements.

Elimination of waste-metal lath

Inward vapor flow due to high temperature gradients as a moisture source in building envelope has been documented, specifically when the exterior cladding is wetted by rain and then exposed to solar radiation. This phenomenon can bring large amount of undue moisture across the envelope assembly with a risk of damage of the wall elements. In this paper, inward vapor flow is applied to five large-scale monitored wall assemblies using a large-scale experimental facility consisting of a spraying array, a radiation array, and a test hut to provide controlled interior conditions. The variables studied include type of cladding (brick and cement stucco), presence and ventilation of air space, type of exterior sheathing (oriented strand board and extruded polystyrene) and type of interior finish (vinyl wall covering and paint). The results show that the presence of vapor tight interior finishes leads to the accumulation of moisture in the interior gypsum board, even in the presence of a vapor tight exterior sheathing. The presence of an air space reduces, but does not prevent moisture accumulation, while connecting the air space to the outdoor seems sufficient to short-circuit the inward vapor flow and prevent moisture accumulation.