Cracking in buildings is a common occurrence and often nothing to panic about. However, understanding the types of cracks and when they might indicate a more serious issue is crucial, especially during property surveys.
What’s the Crack?
Cracks can appear in any building over time due to natural shrinkage and settlement. While most of these cracks are harmless, some may require further investigation to determine their cause and severity. A pre-purchase inspection can help identify these cracks and advise if additional investigation is necessary.
Hairline Cracking
Hairline cracks, typically up to 5mm in width, are the most common type encountered during surveys. These cracks are usually of no structural importance and can be easily filled. External pointing might need to be redone to prevent further deterioration. Sometimes, minor adjustments to doors and windows may be necessary if they start sticking due to the cracks. Recurring hairline cracks can often be masked with a suitable lining.
Extensive Cracking
Cracks between 5mm and 15mm wide are more concerning as they may indicate underlying issues beyond simple settling or dried-out plaster. Cracks of 25mm or wider are especially serious, potentially signalling structural damage or subsidence. Such significant cracks might require major repair work, including underpinning, to stabilise the building.
Understanding Subsidence
Subsidence occurs when the ground beneath a building shrinks, causing the foundations to misalign. It’s particularly problematic when the ground sinks at different rates, leading to uneven settling.
Signs of Subsidence:
- Cracks wider than 3mm (approximately the width of two 1 cent coins).
- Cracks visible both inside and outside the home.
- Diagonal cracks, typically wider at the top than the bottom.
- Cracks located near door or window joints.
Houses Most at Risk of Subsidence
Certain factors increase the risk of subsidence:
- Trees: Large trees or shrubs close to a house can cause subsidence by draining moisture from the soil, leading it to dry out and sink. Approximately 70% of all subsidence cases are linked to tree roots absorbing moisture from the soil.
- Clay Soil: Clay soil is particularly susceptible to weather changes. It can shrink, crack, and shift during hot, dry conditions, making the ground unstable and more likely to sink.
- Leaks: Leaking drains or water mains can soften the soil or wash it away, causing sinkage.
- Age and Construction: Period properties might be at greater risk of subsidence due to shallower foundations compared to more recently built homes. However, older homes constructed with bricks and lime mortar may be more flexible and less prone to damage from ground shifting.
- Mining: Properties near former quarries or pits may be on unstable ground.
What is Underpinning?
Underpinning is a method used to repair structural issues or subsidence by strengthening a building’s foundation. This involves building a new foundation underneath the old, damaged one to provide adequate support. Underpinning can be costly and requires specialist contractors. Fortunately, according to data from the Royal Institute of Chartered Surveyors (RICS) in the UK, less than 10% of properties affected by subsidence require underpinning.
If you notice cracks in your property or need further advice, visit www.isurv.ie or contact us at info@isurv.ie. We’re here to help you assess and address any concerns.