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The purpose of this paper is to present the results of an experimental study aimed at analysing the effect of the roof tile air permeability on the thermal performances of ventilation ducts in the roof. The main reason underlying this study is the fact that the theoretical reference assumed for the manufacture and sizing of ventilation ducts (the accepted theory on roof ventilation) is clearly limited when applied to ducts which are not perfectly airtight (Hens) and results in an oversizing of the ventilation ducts.

A section of roof is built, covered with different tiles and environmental and meteorological data collected. The data are analysed statistically.

The results show that the permeability of the layer of tiles determines heat losses which are in addition to those connected with the stack effect in a perfectly airtight duct with the same features. The results also confirm the correlation which has already been demonstrated between the geometric ratio of the length of the duct divided by its height and the amount of heat dissipated by the roof (Sandberg and Moshfeg).

This study analyses the performance of the roofs only during the summer season. The research is therefore continuing with a long‐term (one year) analysis of the roofs characterised by a high level of roof tile permeability so as to understand the consequences that the presence of a ventilation duct in systems with air permeable roofing may have on the thermal efficiency of the roof.

The repair and maintenance of flat roofs probably creates one of the greatest headaches for a property manager as well as giving a touch of migraine to the professionals and advisers concerned with flat roofing problems. It was probably 15 years ago when we all became aware of the failings in design, construction and maintenance of flat roofs erected in the mid‐sixties and early seventies. The Codes of Practice at the time informed us that flat roofs, if designed and constructed in accordance with the Codes, should be maintenance‐free! Unfortunately this was not the case. Flat roofs, even today, still remain unmaintained with maintenance only being considered when failure actually occurs, when something has to be done. This attitude and approach are changing and today property managers are very much more aware of the importance of keeping flat roofs maintained and in a good state of repair. The property manager can also take comfort from the vastly superior materials that are available on the market now as opposed to ten to 15 years ago. This, however, is not an excuse to become complacent about the obligations of maintaining flat roofs, indeed there is no less obligation now than there was ten years ago; the due process of maintenance must be followed. Maintenance of flat roofing should form part of the designers thinking when detailing and specifying a roofing system. Unfortunately, it is not always possible to achieve maintenance input in terms of design and specification. Consequently, maintenance for flat roofing is only considered on completion of the roof and it is at this stage that maintenance policy must be formulated.

Offers guidelines for surveyors dealing with pitched metal roofs built between the early 1970s and the present. Discusses roof pitch recommendations, insulation, linings, fastenings, leaks, corrosion, and sealants. Summarises that surveyors should consider particular points of corrosion, condensation, leaks and insulations when dealing with metal roofs.

This paper was delivered by the author at a conference on ‘Building Defects in Commercial Property’, organised by Henry Stewart Conference Studies on 7th February, 1985.

This is an initial attempt to classify natural roofing slate quality using the new European Standard BS EN 12326 and suggest how such classification may be employed to predict in‐service performance and identify potentially problematic materials.

A wide range of natural roofing slates has been subjected to the new standard testing regime and additional tests carried out. Experience of known in‐service performance and previous test results have also been taken into consideration.

An initial classification of natural roofing slate quality has been proposed with the flexural strength, water absorption, potential for oxidation and carbonate content considered to be the key components.

There is considerable scope for refinement of the proposed classification by investigating the performance of the wide range of other natural roofing slates available and taking the results into consideration. Predicted in‐service performance is based on practical experience and can be considered only a general guide.

By classifying natural roofing slate quality users will be able to make better informed purchasing decisions based on cost versus quality. Slate producers, especially those with higher quality slates, will also be able to market their materials accordingly with less chance of losing out to lower quality, potentially problematic materials that still conform to the new standard.

The concept of a quality classification for natural roofing slate is not new, but this has been omitted during the creation of the new standard. The proposed classification is broader and probably better defined than those in existence elsewhere or previously used within the European Union member states.

This paper is predominantly concerned with flat roofs of timber construction with which the author is most familiar. The principles discussed are, however, generally applicable to roofs constructed of other materials.

It is not uncommon for designers of low rise buildings to be instructed by their clients that a requirement for a pitched roof is part of the design brief. This may reflect an aesthetic preference by the client, but is more likely to be due to the opinion that the pitched roof is a traditional and well‐tried construction form. While it is true that pitched roofs do have a generally good record of satisfactory performance, especially when compared with some types of flat roof construction, the structural design of the majority of pitched roofs constructed in the last 25 years is very different from those illustrated in textbooks of ‘traditional’ roof carpentry. In addition to use of trussed rafters, other factors, such as increased insulation or the development of the roof space as habitable accommodation, have similarly changed the way in which the roof performs and the areas of consequent potential risk.

Various guides, learned papers and trade articles have dealt with roofing maintenance and refurbishment in the past. This brief paper can therefore only act as a general guide to specifiers requiring information on roofing. Further assistance is obtainable from reputable specialist roofing contractors, British Standards, the British Flat Roofing Council, the Flat Roofing Contractors Advisory Board (FRCAB), the Mastic Asphalt Council & Employers Federation (MACEF) and the National Federation of Roofing Contractors. In addition the Tarmac book ‘Flat Roofing — a Guide to Good Practice’ and the PSA Flat Roof Guides are valuable sources of reference.

Green roofs are still often seen as a pure aesthetical element in architecture, as a spleen of some “greenies”. In fact green roofs already contribute, to some extent, to a better microclimate through evaporation, filtering of dust from the air and a decrease in temperatures at the rooftop. In cities like Berlin and Munich many green roofs have already been realised. Coupled with this microclimate improvement, is the thermal comfort improvement under such roofs by more mass, dry or wet substrate, and shading through the plants. Besides improving the microclimate and the indoor climate, the retention of rainwater is another important advantage. That means an important reduction of the rainwater input in the sewage system during rainfalls, cutting the peak load, avoiding an overload of the system, which might cause flooding and serious health problems. The risk of flooding in cities, which is increasing in many cities due to a ground sealed by buildings, asphalt and concrete, can be diminished. One recent example of the use of green roofs with this purpose is the Potsdamer Platz in the centre of Berlin, where 100 percent of the rainwater has to be evaporated or used for toilet flushing on the building site. Scientific knowledge on green roofs is still limited to temperate climates, due to a development which took place in central Europe. Since 2000 a scientific project in Rio de Janeiro is checking local parameters, like possible vegetation, which can be used and substrate composition. Parallel to this, four prototype roofs, three greened and one blank, are used to measure the retention rate of the rain water and the temperature on the underside of the roofs in order to analyse the possible improvement of the thermal comfort in buildings. This paper will describe the scientific results of Germany and discuss the practicability on a larger scale under tropical conditions.

The induction of geological disasters is predominantly influenced by the dynamic evolution of the stress and plastic zones of the multilayer rock formations surrounding deep-rock roadways, and the behaviours and mechanisms of high in situ stress are key scientific issues related to deep-resource exploitation. The stress environment of deep resources is more complex owing to the influence of several geological factors, such as tectonic movements and landforms. Therefore, in practical engineering, the in situ stress field is in a complex anisotropic three-dimensional state, which may change the deformation and failure law of the surrounding rock. The purpose of this study is to investigate the tunnelling-induced stress and plastic evolution causing instability of multilayered surrounding rock by varying three-dimensional in situ stresses.

Based on data from the Yangquan Coal Mine, China, a finite difference model was established, and the elastic-plastic constitutive model and element deletion technology designed in the study were analysed. Gradual tunnelling along the roof and floor of the coal seam was used in the model, which predicted the impact tendency, and compared the results with the impact tendency report to verify the validity of the model. The evolutions of the stress field and plastic zone of the coal roadway in different stress fields were studied by modifying the maximum horizontal in situ stress, minimum horizontal in situ stress and lateral pressure coefficient.

The results shown that the in situ stress influenced the stress distribution and plastic zone of the surrounding rock. With an increase in the minimum horizontal in situ stress, the vertical in situ stress release area of the roof surrounding rock slowly decreased; the area of vertical in situ stress concentration area of the deep surrounding rock on roadway sides decreased, increased and decreased by turn; the area of roof now-shear failure area first increased and then decreased. With an increase in the lateral pressure coefficient, the area of the horizontal in situ stress release area of the surrounding rock increased; the area of vertical in situ stress release area of the roof and floor surrounding rock first decreased and then increased; the area of deep stress concentration area of roadway sides decreased; and the plastic area of the surrounding rock and the area of now-shear failure first decreased and then increased.

The results obtained in this study are based on actual cases and reveal the evolution law of the disturbing stress and plastic zone of multilayer surrounding rock caused by three-dimensional in situ stress during the excavation of deep rock roadways, which can provide a practical reference for the extraction of deep resources.