• • Title • Why do buildings crack? Other Authors • Building Research Establishment Published • Garston, Watford: Building Research Establishment, 1991. Physical Description • 12 p.: col. Series • • Subjects • • • • • • • • • • • • • • • • Summary • This Digest examines the causes of cracking in buildings and shows, with descriptions and illustrations, the visible results of a wide range of problems. The Digest is a key to other, more specialised, BRE Digests and other publications and does not contain a complete solution to every cracking problem. It aims to broaden the understanding of the factors responsible and increase the likelihood of correct diagnosis and repair.

Avoidance of some of the pitfalls will minimise future trouble in new buildings and lead to better design and workmanship. This Digest replaces Digest 75 which is now withdrawn. Notes • Caption title.

• Replaces Digest 75. • Includes bibliographical references (p. Titarenko om matematika 6611 1. 12) Language • English ISBN • Libraries Australia ID • Contributed by Get this edition.

1 THE SIGNIFIGANCE OF CRACKS IN LOW-RISE BUILDINGS. Johnson CEng. Chartered Civil and Structural Engineer and Surveyor KEYWORDS: Cracks, Cracking, Monitoring, Buildings, Surveys, Inspection. Is that crack serious?

Do not just stand and stare at the cracks – they are unable to speak and will not give you any clue as to their cause. Instead stand back, look at the whole building from a distance. Walk round the building. Look at the condition of adjoining buildings and other features such as trees. Always work from the general to the particular.

Asks the owner of a domestic house a day before they are due to exchange contracts on the sale! Figure 1: This is one of the simplest questions to ask, but for the professional adviser one of the most difficult to answer at least within the timescale demanded by some property owners. Most buildings crack at some time during their service life. The appearance of cracks is a symptom of distress within the fabric of the building. Often the cracking is of little consequence and once it is established as static, simple repair by filling or re-pointing is all that is required. However a crack maybe the first sign of a serious defect which may affect the serviceability or the stability of the building.

1 2 The appearance of cracks can also affect the value of the building, its insurability, the saleability and can be the subject of litigation. Therefore correctly assessing the significance of cracks is essential. However it is a far from a simple task and is often a subjective exercise. The implications of an incorrect assessment can lead to expensive and unnecessary remedial work.

In some instances the remedial work may exacerbate the problem resulting in yet further and more extensive cracking. So how does the professional adviser decide if the cracks are significant? Professor Malcolm Hollis once stated: Surveying buildings is an art, verifying the cause of failure is a science. (Hollis 2000). It is therefore important to develop a methodology or systematic approach so that any action taken is appropriate to the cause. The following methodology should not be followed rigidly because each case will differ on its merits but it provides a systematic method of gathering information and then assessing the significance of cracks.

The first stage of the methodology is the initial inspection: THE INITIAL INSPECTION. During the initial inspection do not give opinions under pressure from the client. If you speak at all confine your comments to asking questions as part of the data gathering exercise. Do not just stand and stare at the cracks they are unable to speak and will not give you any clue as to their cause. Instead stand back, look at the whole building from a distance. Walk round the building. Look at the condition of adjoining buildings and other features such as trees.

Always work from the general to the particular. Structural alterations to the building should be identified or any alterations that may have affect the structural integrity of the building. Note the age of the building and if it has been extended or if any part of the building has been demolished.

Always be suspicious of how a building is constructed. Recent decorations may conceal existing cracks. There is clear evidence this crack has been filled before, probably with cement mortar. The wall appears to be random stone wall laid originally in lime mortar. The repairs to part of the wall with cement mortar can alter the manner in which the wall behaves.

2 3 The pattern of the cracks should be studied. Cracks in masonry generally manifest perpendicular to the line of force, (Bonshor & Bonshor, 1996) although this can be distorted by the relative stiffness of the building elements. Cracks will tend to follow lines of weakness, for example cracks in a wall panel will usually occur between door and window openings which are the areas of weakness Figure 3: The foundation is subsiding due to action of the tree roots. The line of force is diagonal and the cracks are appearing perpendicular to the line of force. The cracks follow the line of weakness, in this case the window openings. The construction materials should be noted.