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Understanding common building defects

Article published in "Majalah Akitek", Volume 16, Issue 1, First Quarter 2004, pg. 19-21

By Associate Professor Dr. A Ghafar Ahmad  School of Housing, Building and Planning Universiti Sains Malaysia, Penang

The practice of securing information on heritage buildings has been considered fundamental towards understanding the existing building conditions and defects. Such detailed and systematic collection and documentation of vital building information is commonly known as the dilapidation survey. In Malaysia and elsewhere, the dilapidation surveys are gaining momentum and are often required by the building owners or clients. Dilapidation surveys are usually prepared in anticipation of the work required to rectify any identified building defect; hence, they are best conducted as part and parcel of the documentation for these works. A poor understanding regarding the extent and nature of the building defects would render an inappropriate approach and scope of repair work being carried out during the conservation project - leading to disagreements and substantial costs implications amongst building owners, clients and contractors.

A dilapidation survey is the practice of identifying and recording building defects through the means of photographic and digital documentation prior to any conservation work. The survey - usually carried out by building conservators - requires in-depth analyses of the building defects, probable causes and the proposed methods and techniques of building conservation. Normally, data and information obtained from the dilapidation survey are analyzed, documented and presented in a technical report: which is used for preparing project briefs, building specifications and the Bill of Quantity (BQ).

As building conservation often involves various remedial works and building repairs, a thorough identification and recording of building defects are integral in determining the appropriate conservation methods and techniques to be employed. Hence, dilapidation surveys involve historians, architects, conservators, structural engineers, mechanical and electrical, and quantity surveyors. Occasionally, the expertise of microbiologists, chemists, archaeologists and geologists are also sought. For instance, in the restoration of the Fort Cornwallis in Georgetown, Penang, microbiologists were consulted on the treatment of harmful growth and fungus stain, whilst archaeologists were engaged to conduct archaeological works, especially in tracing the demolished old fort walls and remnants of the structure. In the practice of building conservation, dilapidation surveys are generally instrumental in regard of the following aspects:

Understanding the state of the building defects

Determining the causes of the building defects

Identifying appropriate methods and techniques of building conservation

Providing reference materials to clients, consultants and project contractors

Providing a vital resource for conducting the Historical Architectural Building Survey (HABS)

As recording and documenting are the basic components of the dilapidation surveys, a thorough investigation of the building conditions, defects and their causes are necessary. The conditions and nature of the existing building materials should be well captured in both photographic and digital forms for purposes of documentation. Existing building materials - whether timber, brick, stone, plaster or concrete - should be fully examined and documented. The same goes for the condition of roof structures, floors, doors, windows, staircases and foundation. Balustrades, pinnacles, cornices or festoons that have been broken or missing in the past should also be noted. The exact locations of all building defects should be marked clearly and plotted onto floor plans, sections and elevations. For cross-referencing purposes, windows, doors, staircases and rooms should be coded.

Studies on heritage buildings in Malaysia have highlighted several building defects that are commonly found:

Fungus stain and harmful growth

Fungal stains or mould occur when there is moisture content in the walls. It flourishes in an environment of high humidity with lack of ventilation. Harmful growth includes creeping and ivy plants that can grow either on walls, roofs or gutters. This usually happens when dirt penetrate small openings in the walls and mortar joints, creating suitable grounds for seeds to grow. Roots can go deep into the existing holes causing further cracks and water penetration.

Erosion of Mortar Joints

The main function of a mortar joint is to even out the irregularities of individual blocks either stones or bricks. Causes of mortar joint erosion include salt crystallization, scouring action of winds, the disintegrating effects of wall-growing plant, and water penetration resulting in dampness. Decayed mortar can be forcibly removed with a mechanical disc or manually raked out using a knife or spike.

Peeling Paint

Peeling paint usually occurs on building facades, mainly on plastered walls, columns and other areas that are exposed to excessive rain and dampness. Some buildings located near the sea may face a greater risk. The amount of constant wind, rain and sun received can easily turn the surfaces of the paint to become chalky and wrinkled or blistered. As is the case in many heritage buildings, several layers of paints have been applied onto the plastered walls over the decades. Apart from lime wash, other types of paints used include emulsion, oil-based, tar, bituminous and oil-bound water paint. Different types of paints require different methods of removal depending on their nature.

Defective Plastered Renderings

Defective plastered rendering occurs mostly on the external walls, columns and ceiling. In a humid tropical climate like Malaysia, defective renderings are normally caused by biological attacks arising from penetrating rain, evaporation, condensation, air pollution, dehydration and thermal stress. Other causes may be the mould or harmful growth, insects, animals and traffic vibration. Prior to being decomposed and broken apart, renderings may crack due to either shrinkage or movement in the substrate.

Cracking of Walls and Leaning Walls

External walls may be harmful to a building if they are structurally unsound. Vertical or diagonal cracks in the wall are common symptoms of structural instability. Such defects should be investigated promptly and the causes diagnosed: be it the foundations, weak materials and joints; or any shrinkage or thermal movements such as those of timber window frames. Diagonal cracks, usually widest at the foundations and may terminate at the corner of a building, often occur when shallow foundations are laid on shrinkable sub-soil which is drier than normal or when there is a physical uplifting action of a large tree’s main roots close to the walls. Common causes of leaning walls include a spreading roof which forces the weight of a roof down towards the walls, sagging due to soil movement, weak foundations due to the presence of dampness, shrinkable clay soil or decayed building materials; and disturbance of nearby mature trees with roots expanding to the local settlement.

Defective Rainwater Goods

Problems associated with the defective rainwater goods include sagging or missing eaves, gutters, corroded or broken downpipes, and leaking rainwater heads. Other problems include undersized gutters or downpipes which cause an overflow of water during heavy rain, and improper disposal of water at ground level. Due to inadequate painting, iron rainwater goods can rust and fracture. Lack of proper wall fixings, particularly by projecting lead ears or lugs can cause instability to the downpipes. If routine building inspections and maintenance have been neglected, rainwater goods can be easily exposed to all sorts of defects.

Decayed Floorboards

Widely used in many heritage buildings including churches, schools, residences and railway stations, some timber floorboards have been subjected to surface abuses and subsequently deteriorated: leading to structural and public safety problems. The main causes are pest attacks, careless lifting of weakened boards by occupants, electricians or plumbers; lack of natural preservatives ; and corroded nails.

Insect or Termite Attacks

Timber can deteriorate easily if left exposed to water penetration, high moisture content and loading beyond its capacity. Insect or termite attacks pose a threat to damp and digestible timber found in wall plates, the feet of rafters, bearing ends of beams and trusses, as well as in timbers which are placed against or built into damp walling. It is unwise to ignore timber that is lined with insect or termite holes because they may in time soften the timber and form further cracks. Affected timber can be treated by pressure-spraying with insecticide or fumigant insecticidal processes.

Roof Defects

As roof often acts as a weather shield, it is important to treat aging roof tiles. In Malaysia, clay roof tiles have been widely used in the heritage buildings. Common defects of roof tiles include corrosion of nails that fix the tiles to battens and rafters, the decay of battens, and the cracking of tiles caused by harmful growth. Harmful growth poses a danger to the tiles because it may lift tiles and create leaks. Another aspect to be considered is the mortar applied for ridge tiles which tends to decay or flake off over the years.

Dampness Penetration Through Walls

Dampness penetration through walls can be a serious matter, particularly to buildings located near water sources. Not only does it deteriorate building structures but also damages to furnishings. The main cause of dampness is water entering a building through different routes. Water penetration occurs commonly through walls exposed to prevailing wet wind or rain. With the existence of gravity, water may penetrate through capillaries or cracks between mortar joints, and bricks or blocks before building up trap moisture behind hard renders. Water may also drive further up the wall to emerge at a higher level. Dampness also occurs in walls due to other factors such as leaking gutters or downpipes, defective drains, burst plumbing and condensation due to inadequate ventilation. Dampness may also enter a building from the ground through cracks or mortar joints in the foundation walls.

Unstable Foundations

Foundations are a critical in distributing loads from roofs, walls and floors onto the earth below. They are structurally important to the permanence of a building and should this be lacking, it is pointless investing on superficial restoration work. Most of the common problems associated with the foundations depend on the geology of the ground upon which a building stands, structural failures as well as presence and height of a water table. Additionally, inherent failures may also happen in a building in which has to cope and carry any unsettled problem of the foundations. Problems of the foundations may lead to an unstable building structure, which is unsafe to users and occupants. Unstable foundations may occur because of several reasons including shrinking clay soil, penetration of dampness and water that may decay walls and foundations; presence of large trees near the building; and the undertaking of excavations nearby. They may also occur due to traffic vibrations, deteriorating of building materials and the increased loads, particularly with a change in building function.

Poor Installation of Air-conditioning Units

Most heritage buildings were built without air-conditioning systems. Where people have to contend with warm temperatures, the need to install air-conditioning systems to meet modern building requirements seems necessary. Subject to the building function, structures and the effects on building fabric, one should consider several factors before installing air-conditioning units in heritage buildings. The cooler and drier air produced by the air-conditioning systems may cause shrinkage of building materials. There may also be a possibility of condensation either on the surfaces or within the structure of the fabric, eventually allowing the build-up of mould. Moreover, it may be difficult installing the air conditioners as evidenced by how units were haphazardly placed on windows or the front façade of some heritage buildings. Such poor practices have gravely affected the appearance of these heritage buildings.

After diagnosing all building conditions, defects and causes, they should be presented with relevant graphics in the dilapidation survey report. The use of information technology may well assist in the preparation of a good-quality report. As a rule of thumb, a dilapidation survey report should contain the following information:

· Cultural attributes and historical background of heritage buildings

· Architectural details and significance of heritage buildings

· Detailed explanation of building conditions, defects and their causes

· Proposed methods and techniques of building conservation

· Proposed scientific studies and tests to be carried out in the project

· Pictorial documentation on building conditions and defects

· Floor plans, sections and elevations indicating the locations of building defects

It is essential to recommend in the dilapidation survey report the proposed scientific studies and tests to be carried out during any conservation work. Such scientific studies and laboratory tests are important as they provide additional information that can lead to solving related building problems or defects. Common scientific studies required during the conservation works include microbiological studies to identify plant species, dispersion agents, control ranking and chemical fungicides; archaeological studies to trace hidden remnants; and the study of relative humidity to gauge the local temperatures and air moisture levels. Some examples of the laboratory tests required are the brick test to analyze the compressive strength and level of porosity; the timber test to identify timber species, grading and group strength; lime plaster to determine the component elements through X-ray Fluorescence (XRF) analysis; the salt test to detect the salt levels and the percentage of total ions; and the paint test to classify paint types as well as colour scheme analysis. All data and analyses generated from the scientific studies and laboratory tests should be presented in separate reports.

To be effective, the practice of the dilapidation survey should involve a multidisciplinary approach which requires in-depth knowledge in conservation as well as other related fields in order to correctly assess building defects, determine their causes, and propose restoration methods. Relevant scientific studies and laboratory tests are equally important as these results provide for a sound basis for decision-making in conservation works. Callous incidences of improper diagnoses of building conditions, and the resultant ineffective remedial measures may pose unnecessary threats to the heritage building structures and raise concerns over public safety. It is imperative, therefore, to invest some resources in conducting the dilapidation survey prior to any conservation project. The dilapidation survey report, once completed, serves as an indispensable archival resource for future references and cyclical building maintenance programmes.


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