It's a cracking blog | RMSurveyors
When viewing a property for purchase, most homebuyers will be concerned about cracks and often ask me ‘is that crack serious?’.
It’s normal for buildings to move and a small number of narrow cracks to appear over time, and many can be easily repaired with some simple repointing or plastering.
However, depending on their size and location, cracks can indicate stress within the fabric of a building and the first sign of a more serious defect. In such cases, the services of a structural engineer may be required to assess the cracks and any remedial work, potentially resulting in substantial costs – which may affect the price you’re willing to pay for a property.
In my commitment to making Home Surveys simple and easy to understand, in this blog I’ll be breaking down some common causes of cracking and the different types of cracks to look out for.
But first, a quick heads up for homebuyers: The Building Research Establishment (BRE) has identified 6 categories to rate external cracks on a scale of 0–5, with 0 meaning no action is required and 5 meaning major repairs are necessary.
These categories are used as an industry standard by engineers, surveyors and insurance companies alike. However, take care when looking at this guide as it’s possible for an untrained person to misinterpret it – for example, in some cases a new 1mm crack can be indicative of a more serious matter than an old 25mm crack.
Common causes
Cracks in brick or concrete walls can be caused by a number of factors, including:
Thermal movements: this is the expansion and contraction that occurs in a building’s walls when there are seasonal changes in temperature. For example, masonry heats up and expands during summer and cools and contracts during winter, which can lead to cracking. Although this type of crack doesn’t look great, it isn’t structurally dangerous.
Changes in moisture content: there can be significant changes to the moisture content of many building materials after construction, especially during the first few months. These changes lead to the expansion or contraction of materials, potentially resulting in cracks. For example, clay bricks tend to expand with moisture initially, while concrete blocks can dry out and experience shrinkage.
Incompatible building materials: the use of different materials in a building can result in cracks. One example is plaster applied over the junction between two different materials such as blockwork walls and timber partitions.
Settlement: also known as consolidation or compaction, this is the downward movement of the site on which a property stands, due to the weight of the building. This downward moving ground can produce cracks in the building. This is no to be mistaken for subsidence.
Subsidence: this is where the moisture content of the (usually clay) soil is reduced, causing it to shrink and pull the property’s foundations down with it and potentially resulting in cracks. It can be caused by prolonged dry spells. It may also be caused by trees and shrubs which can absorb significant volumes of water from the soil. It can also be associated with leaking drains which wash away the supporting soil causing the foundations to drop.
Heave: this is the upward movement of the ground beneath a building when dry soil expands due to an increase in its moisture content, and can also cause cracks in a property.
Chemical attack: chemical reactions that potentially produce cracks include sulphate attack which can occur in mortar and concrete ground floors, carbonation of exposed concrete and corrosion of wall ties. Cracks due to chemical attack differ from changes due to temperature and moisture, and they continue for as long as conditions remain favourable to the reaction and further reactive materials remain available.
Lack of lateral restraint: this is the most common cause of bowing or leaning walls. Traditionally, restraint is provided by the bonding in of internal and party walls or by the floor joists. Inappropriate alteration can remove the lateral restraint from a wall, causing it to bow and crack.
Concentrated loading: this can occur when structural alterations to a building – such as the removal of internal walls or the enlargement of external windows or doorways – or a change of use can cause stress concentrations within localised areas of supporting brickwork. This will often occur when the work is not done by a qualified builder.
Types of Crack
Here are some of the most common types of crack to look out for:
Internal hairline cracks are usually less than 1mm in width, and are generally caused by changes in temperature or moisture content. They are typically seen along board joints and are not considered to be indicative of a serious structural problem. This type of crack should be filled, prior to re-decoration, as part of routine maintenance. However, some new cracks can be more significant and need to be observed or investigated further as they may be an indication of a more serious problem. This is where the opinion of a chartered surveyor can be of use.
Shrinkage cracks tend to be seen where solid masonry walls meet hollow stud partitions, but these are normally of no structural significance and can be simply filled during re-decoration works. However, they may open up again from time to time.
Cracks to external brickwork can mostly be pointed to prevent damp penetration, as part of normal maintenance. Due to the nature of brickwork, the cracks may open up again from time to time and may therefore need regular repair or a flexible filler. If however the crack is a diagonal crack wider at the top than at the bottom or a vertical crack wider at the base that the top you should seek professional advice.
Help for homebuyers
If you’re in the process of purchasing a property, don’t be caught out by cracks
A detailed RICS Home Survey will arm you with all the information you need, alerting you to the presence of concerning cracks and the type of remedial work that may be required.
I offer RICS Home Surveys in and around south London and my reports are always clear and easy to understand. I also offer a free Zoom or phonecall after the inspection to take you through my findings and answer any questions you may have.
Contact me today at roo@rmsurveyors.co.uk or on 07957 606886 to have an informal conversation about your requirements.
Thanks for reading, I hope this was useful – and I wish you a cracking day!
Roo x
