An Introduction to Structural Movement and Cracking by Jen Lemen

What causes structural movement?

Buildings move all the time! Usually so slight or slowly though that the movement is not noticeable. The physical sign of structural movement is usually cracking to a building, externally and/or internally.

Movement can be caused by one or more reasons. These can be split into causes relating to the structure and causes relating to the ground. 

Structural causes include:

• Shrinkage of building materials, such as when mortar, plaster or concrete (which all have a high water content) dry out and shrink
• Moisture or thermal (seasonal or weather-related) movement, causing building materials to contract or expand 
• Poor workmanship or design detailing, e.g. removal of a chimney breast, overloaded floors or roof alterations
• Decay or deterioration of building fabric, e.g. rotten timbers

Ground-related causes include:

• Settlement, where foundations are too shallow or have insufficient load bearing capacity for the weight of the building
• Subsidence, where the ground beneath the building is unstable. For example, due to mining or excavation works nearby, trees nearby (causing the soil to lose moisture) or prolonged dry weather conditions
• Heave, where there is upward movement of the ground. This could be due to clay soil swelling when wet or the removal of nearby trees (which releases a large amount of water into the ground)
• Defective drainage

Diagnosing the cause of structural movement can be very complex. 

How does cracking relate to the APC competencies?

Where a candidate has Building Pathology to level 3 in the RICS APC, such as for a Building Surveyor, you need to be following the trail, analysing the potential causes of the cracking and advising on the most likely cause or causes, alongside remedial works.

However, if you only have Inspection to level 3 (and no Building Pathology competency), e.g. as a Commercial Real Estate candidate, then you would not be expected to analyse a defect. You would instead be reporting what you saw (using comprehensive notes and photographs) and

recommending that your client seeks specialist advice. 

You cannot simply be ignorant to the issue though – you need the requisite knowledge of construction and defects to be able to identify and provide diligent advice to your client. This is a common area of referral, particularly on the Inspection competency.

However, a candidate in this position should not seek to give in-depth advice on building pathology as this would be outside their scope of experience. 

This all comes back to advising or acting within your scope of competence. Know what you should or not be advising on and how far you can go in giving advice (or recommending that a specialist provides that advice instead) is key to demonstrating competence.

How can I report on cracking?

For candidates with Building Pathology as a level 2 or 3 APC competency, you should keep detailed site notes and photographs of any cracking observed. 

Cracks come in many forms:

• Hairline cracks
• Stepped cracks
• Vertical cracks
• Cracks that are wider at one end
• Horizontal cracks
• Cracks that mirror internally and externally

The type and nature of the crack is likely to give an indication of it’s cause. An excellent book to read is a Practical Guide to Diagnosing Structural Movement in Buildings by Malcolm Holland.

You should also record the position and direction of cracks on sketch diagrams or plans of the building elevations. 

Physical inspection on site should include:

• Determining the approximate age of the cracks, e.g. are they clean or has dirt accumulated in the crack?
• Measuring the dimensions and configuration of the crack
• Recording the materials, finishes and condition of the building materials and wider construction

BRE Digest 251 Assessment of damage in low-rise buildings provides a helpful guide to assessing cracking to buildings. There are six categories, 0-5, based on the width of the cracking observed and with associated remedial advice:

• 0 – hairline cracks <0.1mm – negligible and no action required
• 1 – fine cracks up to 1mm – repaired through normal decoration
• 2 – cracks up to 5mm – easily filled or re-pointed and doors or windows eased and adjusted 
• 3 – cracks of 5-15mm – may require opening up and patching or repointing
• 4 – extensive damage, cracks of 15-25mm – may require breaking out and replacing sections of masonry, particularly over windows or doors
• 5 – structural damage, cracks >25mm – likely to require partial or complete rebuilding

We would recommend purchasing a copy of the Digest from BRE, as it is essential reading and contains a lot of helpful detail and advice.