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Environmental reasons of urban deterioration Alaa Ibrahim Al Farahaty Faculty of Engineering, Architecture department Alexandria University, Alexandria, Egypt. [email protected] Abstract: Urban buildings are frequently subject to numerous forms of deteriorations, regularly in the form of dampness, wall cracks, peeling of finishing , declining of foundations or even a water penetration to the building . That is beside other factors that could eventually lead demolishing of the whole structure. Even as some of these factors that cause the building defect may be instantly noticeable in several cases, in others these factors are not so understandable. Without doubt, the environmental circumstances are among the main factors of building deterioration. These circumstances have natural effects without human intervention and frequently appear over several years depending of the state of the structure. The environmental causes of deterioration are derived from different shapes .For instance, sun effects, wind effects and moisture effects. Each effect has specific results and influences on the building structure elements. Therefore, an accurate cause of a building defect and the form of its appearance should be understood prior to a sensible remedy can be applied. An exact identification of a building defect necessitates knowledge and familiarity with the design and construction of a building combined with an indulgent of methods of scientific exploration. Keywords: Environmental circumstances, Deterioration causes, Sun effects, wind influences, moisture consequences. 1- Introduction Therefore the high temperature causes deteriorating of the organic materials (eg, wood, textile, pigments etc) besides causing fade of colors, brittle surfaces and peeling of paint from the walls. The level of the deterioration depends on the material elasticity, resistance and the amount of the evaporating internal moisture. The three main factors of the environmental circumstances that deteriorate the buildings structure are the sun effects, moisture effects and wind effects. Depending of the state of the building, these factors influences are adequate to destroy the main elements and materials of any structure. The paper illustrates the three deterioration factors and their consequences on 2.2 Thermal expansion:the building's stability and longevity. The actual temperatures can lead to 2- Sun Effects either temporary or even permanent changes 2.1 Solar radiation:in physical and chemical properties of the Band of radiation of Ultra violet and material, Changes of the temperature are infrared radiation are absorbed by all forms of relevant to assess the consequences of materials, causing increasing of temperature. thermal expansion and contraction as Materials are varied at the temperature materials expand during heating and contract absorption amount depending on the angel of during cooling. The external wall materials are the sun ray, wind effect, the thermal expansion vulnerable to the sun temperature that leads and the characteristics of the material. Some materials surfaces temperature after while of to storing the temperature and transforming absorbing are greater than the surrounding air it slowly and gradually to the internal surface. temperature. Pambo Fernandez, S.,1999 Factors influencing salt- induced weathering of building sandstone, Phd Diss.The Robert Gardon University. Md Azree Othuman Mydin,2012, Hanizam Awang, Factors of Deterioration in Building and the Principles of Repair, ANUL XIX, NR. 1 1 4- Moisture Effects At the night the external wall is cooled and loses its stored temperature causing difference ` temperature degree from the internal and in the external walls. For the low resistance material, repeating this process causes deterioration of the external surfaces features and Imbalance of the architectural elements. That besides devastating of the joints of the inner and the Uncontrolled moisture is the most prevalent cause of deterioration of structures. It leads to erosion, corrosion, rot, and ultimately the destruction of materials, finishes, and eventually structural components. The challenge to preservation professionals is to understand the patterns of moisture movement in order to better manage it-not to try to eliminate it as there is never a single answer to a moisture problem. Diagnosis and treatment will always differ depending on where the building is located, climatic and soil conditions, ground water effects, and local traditions in building construction. 3- Wind Effects The wind properties differ due to the direction, sources, the passed natural geographical places and the season in which the wind blows. The wind degree of velocity is considered the main source of assessing the wind limits of benefits and damages. As the velocity of the wind increases, it has severe effects on the buildings. Roof coverings (eg. tiles, slates, lead and copper sheet) can be lifted in a high wind. Wind is considered one of the main reasons of building humidity as the wind carry the rain water and vapor to the building walls and materials where deterioration and damage takes place. The wind carried the vapors in to the wall of the heritage buildings causing crystallization of water salts then depositing in the walls. Therefore on the long term, the walls plaster and featured deteriorated. When the wind hits the side of the building ,the exposed side of a building can therefore be subject to a “pushing” action, while the protected side can experience a “suction causing long cracks severe at the exterior material .One the long term the exterior walls materials can be deteriorated and lose the historical features. Wind causes loading and mechanical damage to structures. Wind and weather affect building materials, and after long-term action the abrasive impact can lead to significant changes to all exterior parts of the structures and cause erosion of building material .The flow around structures has a substantial influence on the deposition of pollutants, biological corrosion, cycles of drying and wetting, as well as mechanical wear of the exposed surfaces. 4.1 Main Sources of moisture: Above grade exterior moisture Below grade ground moisture Leaking plumbing pipes and mechanical Interior moisture Moisture from maintenance material 4.1.1. Above grade exterior moisture:Due to the buildings age , buildings are notoriously "drafty," allowing rain and damp air to enter through deteriorating materials as a result of deferred maintenance, structural settlement cracks, or damage from high winds or storms. - Most common causes of exterior leaks: Wind driven rain may enter through deteriorating materials such as brick and mortar. Excessively absorbent materials, such as soft sandstone, become saturated and can allow moisture to dampen interior surfaces. Dump air through missing mortar joints; around cracks in windows, doors, and wood siding; and into insulated attics. Hung gutters or drip edge. Improperly installed roofing, or a roofing type, which is incorrect for the slope of the roof involved. Md Azree Othuman Mydin, Hanizam Awang,2012, Factors of Deterioration in Building and the Principles of Repair, ANUL XIX, NR. 1, Philip H. Perkins,1976, Concrete Structures: Repair, Waterproofing and Protection, N3 2 4.1.2. Below grade ground moisture - Most common causes of ground leaks: : Rain water is often referred to as "bulk ``` moisture" in areas that receive significant annual rainfalls or infrequent, but heavy, ` precipitation. When soil is saturated at the base of the building, the moisture will wet footings and crawl spaces or find its way through cracks in foundation walls and enter into basements Moisture in saturated basement or foundation walls-also exacerbated by high water tableswill generally rise up within a wall and eventually cause deterioration of the masonry and adjacent wooden structural elements Builders traditionally left a working area, known as a builder's trench, around the exterior of a foundation wall. These trenches have been known to increase moisture problems if the infill soil is less than fully compacted or includes rubble backfill, which, in some cases, may act as a reservoir holding damp materials against masonry walls Modern source of ground moisture is a landscape irrigation system set too close to the building. Incorrect placement of sprinkler heads can add a tremendous amount of moisture at the foundation level and on wall surfaces 4.1.3. Leaking plumbing pipes and mechanical:- Most common causes of Leaking plumbing pipes: Slow leaks at plumbing joints hidden within walls and ceilings can ultimately rot floor boards, stain ceiling plaster, and lead to decay of structural members. Central air equipment, have overflow and condensation pans that require cyclical maintenance to avoid mold and mildew growth and corrosion blockage of drainage channels. Broken subsurface pipes or downspout drainage can leak into the builder's trench and dampen walls some distance from the source Insulated forced-air sheet metal ductwork and cold water pipes in walls and ceilings often allow condensation to form on the cold metal, which then drips and causes bubbling plaster and peeling paint. 4.1.4. Interior moisture:- Most common causes of interior moisture: Moisture can form on single-glazed windows in winter with exterior temperatures. Frequent condensation on interior window surfaces is an indication that moisture is migrating into exterior walls, which can cause long-term damage to historic materials. When one area or floor of a building is air-conditioned and another area is not, there is the chance for condensation to occur between the two areas. Most periodic condensation does not create a long-term problem. Unvented mechanical equipment, such as gas stoves and driers generate large quantities of moisture. Moist interior conditions in hot and humid climates will generate mold and fungal growth 4.1.5. Moisture from maintenance and construction materials:- Most common causes: Moisture from maintenance can cause damage to adjacent historic materials. Careless use of liquids to wash floors can lead to water seepage through cracks and dislodge adhesives and curl materials. High-pressure power washing of exterior walls and roofing materials can force water into construction joints where it can dislodge mortar, lift roofing tiles, and saturate frame walls and masonry. Replastered or newly plastered interior walls or the construction of new additions attached to historic buildings may hold moisture for months; new plaster, mortar, or concrete should be fully cured before they are painted or finished Md Azree Othuman Mydin, Hanizam Awang,2012, Factors of Deterioration in Building and the Principles of Repair, ANUL XIX, NR. 1, Philip H. Perkins, , 1976., Concrete Structures: Repair, Waterproofing and Protection 3 4.2 Indications and effects of Moisture:4.2.1 Efflorescence:- All molds share the characteristic of being able to grow without sunlight; mold needs only a nutrient source, moisture, and the right temperature to proliferate. Mold can eventually cause structural damage to a wood framed building, weakening floors and walls. Efflorescence is the white chalky powder that you might find on the surface of a concrete or brick wall. It can be an indication of moisture intrusion that could lead to major structural and indoor air quality issues. Building materials, such as concrete, wood, brick and stone, are porous materials. Porous materials can absorb or wick water by a process called capillary action. The moisture that creates efflorescence often comes from groundwater. -Capillary action:- 4.2.3 Rusts:Rusting is a type of corrosion and it is caused by the interaction of water and iron or steel in the presence of oxygen. Rust is a hydrated iron oxide which although solid in form is weak and brittle The rust-induced expansion in strip ties can lead to secondary damage, such as a redistribution of loads, buckling and bulging of wall The rust will have a significantly greater volume than the original metal. This expansion of the tie may cause cracking and distortion of the structure. Cracking will also reduce the weather resistance of the wall, which in turn accelerates the rusting process. The portion of the tie in the outer leaf will usually be the most severely affected because of exposure to rain penetration. However, condensation may also produce enough moisture to allow rust failure to occur. Salts dissolved by groundwater can be transported by capillary action through porous soil. Building materials in contact with soil will naturally wick the water inward and upward. Concrete footings: they are typically poured directly onto soil without any capillary break. Sometimes this is called rising damp. This is the beginning of how water can wick upward into a structure When the capillary flow of water reaches the surface of a building material, evaporation occurs. As the water evaporates, salt is left behind. The potential for damage is increased because of the repetitive nature of the mechanical action caused by the cycle of re-dissolving and re-crystalizing. The action of water rushing to the surface due to capillary action creates incredible forces that can cause materials to crack, flake and break apart. The pressure from can create incredibly strong hydrostatic pressure that can exceed the strength of building materials, including concrete 4.2.2 Molds:Molds are part of the natural environment. Molds are fungi that can be found anywhere inside and outside .When excessive moisture or water accumulates indoors, mold growth often will occur, particularly if the moisture problem remains. While it is impossible to eliminate all molds and mold spores, controlling moisture can control indoor mold growth. Pambo Fernandez, S, 1999, Factors influencing salt- induced weathering of building sandstone, Phd Diss.The Robert Gardon University. Md Azree Othuman Mydin, Hanizam Awang, 2012,Factors of Deterioration in Building and the Principles of Repair, ANUL XIX, NR. 1. 4