What are subsidence cracks?

Subsidence cracks are one of the most common signs of structural movement. They are caused by instability in the ground beneath a property's foundations. The cracks can can appear both internally and externally, often forming in walls, around doors and windows, or in brickwork where the building is under stress. As the foundations move, the structure above it shifts which creates cracks that may widen over time or become more noticeable during periods of prolonged dry weather. While not every crack is caused by subsidence, cracks associated with structural movement should always be assessed by an expert to determine the underlying cause and whether remedial work is required.

A hairline crack in an internal home wall

Hairline Cracks in Plaster

Thin, fine cracks that look like a strand of hair are very common. They often appear in new homes as the plaster finishes drying, or in older homes due to seasonal movement. As long as they don't grow, these hairline cracks in plaster are usually not a cause for concern. However, it is important to monitor them and check inside and out for other cracks that could indicate a wider subsidence issue.

Vertical cracks in an interior wall of a residential home

Vertical Cracks

Cracks that run straight up and down a wall often align with the seams of plasterboard. These can be caused by poor taping during construction and are generally not a structural issue. However, if a vertical crack is wide or continues to grow, it's worth getting it checked.

A large horizontal wall crack extends along an internal house wall

Horizontal Cracks

Horizontal cracks in walls can be more serious. A horizontal crack could indicate a problem with the foundation or, in some cases, a sign of moisture damage causing the wall studs to bow. These should always be inspected by a professional.

A stair step crack in brickwork on an external residential home wall

Diagonal Subsidence Cracks

This is the classic sign of structural movement and subsidence. Diagonal cracks often appear suddenly, running out from the corners of windows and doors. They are typically wider at one end and may look like a 'stair-step' pattern in brickwork. If you see a diagonal crack in an internal or external wall, it is a strong signal that your home's foundation may be moving.

Close up view of exterior home wall crack with crack measuring meter attached.

A 5-Point Checklist

How diagnose a subsidence crack

It's time to call an expert for a professional opinion if you notice any of the following:

The crack is wider than a 10p coin (approximately 3mm)

The crack is diagonal and looks like a stair-step in your brickwork

The crack is visible on both the inside and outside of your home

You have multiple cracks appearing

The crack is accompanied by other signs of movement, such as sticking doors, sloping floors, or gaps appearing around skirting boards

What is subsidence?

The Next Step

Getting a clear diagnosis

If you've seen any of the cracks illustrated above, the next step is to get a professional diagnosis to understand the root cause. Geobear are the UK's leading experts in investigating and solving issues related to ground movement and subsidence. We provide a free online assessment to identify any issues that could be subsidence and will advise on the appropriate course of action.

Free subsidence assessment

Frequently Asked Questions

Subsidence cracks are typically diagonal, often looking like a 'stair-step' in brick or blockwork. They are usually wider at the top than the bottom and tend to appear around weaker structural points like doors and windows. A key warning sign is seeing the same crack on the outside wall.

You should seek an expert opinion if a crack is wider than a 10p coin (approx. 3mm), is growing, or is diagonal. If the crack appears alongside other signs like sticking doors, sloping floors, or skirting boards pulling away from the wall, it is a strong indicator of a potential structural issue.

In most cases, no. Fine hairline cracks in plaster are very common and are usually caused by the plaster drying or minor seasonal expansion and contraction of the building. As long as they are not growing or accompanied by the other warning signs, they are typically just a cosmetic issue.

The best first step is to get a professional diagnosis to understand the true cause of the crack. Contact the Geobear team for a consultation. We can help you understand what's happening and recommend the right solution to give you peace of mind.

Find out for sure

Worrying about wall cracks is stressful. The best way to get peace of mind is with an expert opinion. Our team can conduct a professional site assessment to identify the cause of the cracks and give you a clear, straightforward report on the health of your property.

Contact an expert
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