What Are Stair Step Cracks?

Stair step cracks are cracks that run along the mortar joints in brick walls, which create a stepped pattern resembling a staircase.

Typically, found in brickwork, block walls or masonry, these cracks are commonly linked to foundation movement, structural settlement or subsidence. Stair step cracks tend to be diagonal and usually visible outside; however, they can also appear on walls inside the property.

Mortar joints are the weakest points in masonry, which mean natural cracks appear here. When part of a building settles unevenly or moves, the stress is released in this stepped pattern. 

If you’re comparing different types of cracks, you may find it useful to read our guide on structural cracks.

What Causes Stair Step Wall Cracks?

These distinctive cracks are usually the visible result of movement from within the structure or beneath it. Some of the most common causes are listed below:

1. Foundation Settlement

Although all buildings settle slightly over time, if this settlement is uneven, then problems can occur. This is known as differential settlement. If one part of the foundation sinks more than the other, then the walls above it will experience stress. This results in stepped cracks in the walls.

2. Subsidence

If the ground beneath a property loses volume or strength, subsidence can occur, especially in areas dominated by clay soils, which shrinks during dry spells and swells during intense periods of wet weather. Additional factors that cause subsidence includes, prolonged drought, tree roots extracting moisture from the soil, leaking drains, and poor surface water management. Subsidence is one of the most common causes of stair step cracks in brick walls.

3. Ground movement & soil conditions

Expansive soils and seasonal changes can greatly affect ground movement. Over time, the repeating cycles of shrink-swell activity places increasing pressure on masonry, which results in stepped wall cracks. Alterations to load bearings such as adding an extension or removing walls can also cause ground movement.

Unlike horizontal cracks, which usually suggest lateral soil pressure, stair step cracks often indicate vertical or diagonal movement linked to the foundations.

4. Hydrostatic pressure

Intense, heavy rainfall and poor drainage can result in a build-up of water pressure against the foundations. The pressure can cause the walls to crack.

Stair step cracks often suggest vertical or diagonal movement related to the foundations, unlike for example, horizontal cracks which typically indicates lateral pressure.

Are step stair cracks a sign of something serious?

Not all stair step cracks are an indicator of structural issues, but they should not be ignored. The key factor is identifying whether the movement is historic or ongoing. Below are some of the warning signs, which may indicate a professional assessment is needed:

• The crack is wider than 3mm

• It continues to grow over time

• It runs through multiple bricks

• Sticking doors or windows

• There is viable displacement in the brickwork

• The crack appears internally as well as externally

If you notice several of these signs, then the cracking may signal active movement and is not a historical issue.

Found a stair step crack? Don’t ignore it and do this instead

If you see a crack, there’s no need to panic, but ignoring it can mean the problem will worsen over time. Following the steps below will help you understand what’s happening.

Step 1: Monitor the crack

Keep an eye on the crack, measure the width and take dated photographs. Examine it again after seasonal changes, especially following wet winters or dry summers to check if the crack was grown wider or longer.

Step 2: Check for related signs

Look for any issues that accompany the crack, for example, uneven floors, gaps around window frames, or jammed doors or windows. These signs can indicate underlying movement and often appear together when foundations are affected.

Step 3: Book a professional assessment

A professional assessment involves identifying the root cause, rather than just the surface damage. As specialists in diagnosing ground and foundation movement, Mainmark can recommend non-invasive stabilisation solutions that address the underlying issue.

How do stair step cracks get fixed?

Stair step cracks can be fixed using a range of methods and depends on whether the movement is historic or ongoing.

• Cosmetic repairs – minor repair work may be suitable when movement has stopped.

• Structural stabilisation – this is required when cracks are caused by active movement. This can involve strengthening the ground beneath the foundations or improving load distribution.

• Ground improvement solutions – this can increase the bearing capacity of weak soils without the need for excavation.

• Foundation strengthening – this method ensures long-term stability and prevents further cracking from developing.

It’s important to address the underlying cause as just fixing the crack is ineffective and results in reoccurring cracks. Uneven foundation support resulted in cracked walls at a Victorian villa in Prestwich, Manchester. Mainmark were able to stabilise the ground using Teretek® resin injection, which strengthened the soil and gently re-levelled the structure and prevent further cracking.

Stair step cracks don’t always mean disaster

Although stair step cracks can be a sign of ground movement or subsidence, they don’t instinctively mean that the house is in danger. In most cases, they highlight historic settlement or seasonal ground movement, which can be managed once the conditions are fully assessed.

Identifying the cracks early and engaging with ground engineering specialists is key to determining the cause of stair step cracks. Early intervention allows homeowners to protect their properties and prevent extensive, unnecessary repairs. Mainmark specialises in identifying, diagnosing and resolving the underlying causes of ground movement and offers a range of long-term solutions.

If you’re concerned about any stair step cracks in your home and are looking for expert advice, speak to a specialist today.