House Cracking and Cracks in Masonry Walls

House cracking is a common structural issue that can affect both new and older homes. Cracks may appear in walls, ceilings, floors or foundations. Most of the time, small cracks are nothing to be worried about, however, severe cracks can indicate serious structural issues. House cracking should not be ignored, so it is important to get cracks inspected by a professional when they appear. Understanding the types of cracks and their causes is crucial for effective diagnosis and repair. The following information will address types of cracks, their causes, house cracking in Adelaide specifically, as well as prevention and repair methods.

 

Types of Cracks

Cracks in houses can vary by size, shape, location and orientation. The most commonly seen cracks include:

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When is cracking a concern?

The following table from the Australian Standard for Residential Slabs and Footings outlines the severity concern of differing crack widths. If you have very thin cracks, they most likely are of no risk and do not need repairing. If you have cracks bigger than 5mm, that is when the cracks need to start being repaired. Cracks on the smaller side of 5mm can be easily repaired by being filled in with sealant. If you have cracks wider than 5mm but less than 15mm or multiple cracks together that are larger than 3mm, this is considered moderate cracking and its typically repaired by replacing a small section of the wall where the cracks are. These types of cracks may cause some issues in the home such as doors and windows sticking, service pipes fracturing and weather tightness of the house being lessened. If the damage of the crack is between 15mm and 25mm, then the cracking is severe and needs urgent attention. This can affect multiple areas of your home such as windows and doors distorting, walls leaning or bulging, loss of bearing in beams and service pipes being disrupted. Repairing this sort of damage involves replacing the entirety of the walls affected. It is crucial that this sort of damage is attended to immediately to not cause further issues, as leaving it could result in having to vacate the house if it becomes so severe that it is no longer safe to live in.

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Table 1: Classification of Damage with Reference to Walls

Australian Standard for Residential Slabs and Footings (AS 2870-2011)

Description of typical damage and required repair	Approximate crack width limit	Damage category
Hairline cracks.	<0.1mm	0 Negligible
Fine cracks that do not need repair.	<1mm	1 Very slight
Cracks noticeable but easily filled. Doors and windows stick slightly.	<5mm	2 Slight
Cracks can be repaired and possibly a small amount of wall will need to be replaced. Doors and windows stick. Service pipes can fracture. Weather tightness often impaired.	5mm to 15mm (or a number of cracks 3mm or more in one group)	3 Moderate
Extensive repair work involving breaking out and replacing sections of walls, especially over doors and windows. Window frames and door frames distort. Walls lean or bulge noticeably, some loss of bearing in beams. Service pipes disrupted.	15mm to 25mm but also depends on number of cracks.	4 Severe

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Causes of Cracking

Cracks can originate from a variety of structural and environmental factors. The most common causes are:

Soil Movement

• Movement causes stress on the foundations which leads to cracking.
• Seasonal changes can cause the soil to get wet and dry in different periods. This causes movement as the soil swells up when its wet but shrinks down when its dry.
• When one part of the footing is on dry soil and another part becomes very wet, it causes the building to distort.
• All soils are prone to erosion which can result in some movement.
• Shear failure occurs when foundational soil is not strong enough to support the weight of the footing.

Settlement

• Immediate settlement occurs when a house is first placed on the foundation soil which results in compaction of the soil due to the weight of the house.
• Consolidation settlement may occur from expulsion of moisture from soil or from the soils lack of resistance to being compressed. This usually happens within the first few months of construction, however, it does sometime occur many years later.

Materials

• Brickwork tends to expand slightly over time.
• Timber, plasterboard and concrete often shrink as it ages.

Poor Construction

• Insufficient soil compaction.
• Low quality materials.
• Inadequate foundation depth.

Tree Roots

• Trees planted too close to houses.
• Tree roots can take moisture away from the soil underneath the foundations. This causes the soil to dry up and shrink resulting in footing settlement.
• Common trees to cause issues have been swamp mallets, peppercorn, oak, fig and eucalyptus trees.

Plumbing Issues

• Leaking pipes can cause the soil underneath the house to get wet, which causes uneven settling and swelling.

Aging

• Housing materials degrade over time. This usually is the cause of minor cracks in older houses.

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House Cracking in Adelaide

Soil Type

• A lot of houses in Adelaide are built on reactive clay soils, particularly in the city and North-Eastern suburbs.
• Reactive clay soils expand and contract dramatically with moisture changes. They also exert uneven pressure on foundations as they move, which causes cracks.
• Brick houses built on black earth and reactive clay soil have the worst cases of house cracking.

Climate

• Dry summer periods and inconsistent heavy rain contributes to soil shrinkage and swelling.
• Most reports of house cracking have been made in the dry summer season.
• Long droughts followed by sudden rain is also an issue.
• Minor cracks tend to appear more in Autumn.

Development

• Some newer suburbs are built on reclaimed or poorly compacted land.
• This can lead to increased ground movement over time.

Adelaide Areas

• Residents living in Wayville, Westbourne Park and Goodwood report the most house cracking issues. Suburbs nearby such as Netherby, Kensington, Kingswood, Linden Park and Hectorville have also had issues but less severely.
• Houses built in Newton, Hope Valley, Holden Hill, parts of Gille Plains and Hillcrest are said to have been built on Adelaide’s worst soil.
• Eastern Adelaide is known for its use of the Bay of Biscay soil. This is a reactive clay soil that has been known to cause structural damage to older houses due to the constant shift between shrinking and swelling.
• Residents in Northfield, Adelaide CBD, North Adelaide and Southern Adelaide Hills have most reported house cracking in dry weather in particular.
• Suburbs with sandy soil such as Port Adelaide, Semaphore, Ottoway, Tennyson and Wingfield are some of the safest areas from cracking. This is because sandy soil drains quickly, meaning that the soil does not swell or shrink from moisture because water is never able to absorbed.

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Prevention and Repair

Prevention measures

• Soil testing before construction.
• Proper foundation design based on soil reactivity.
• Maintaining consistent soil moisture levels around the house.
• Avoid planting large trees too close to the house.
• Concrete or similar pathing around the perimeter of the house to help keep stable soil conditions.
• Use control joints up and down the walls to accommodate movement without losing strength or appearance.
• Stormwater and controlled landscaping to keep the house more stable.

Repair solutions

• Fill minor cracks with flexible sealant or render.
• Moderate cracking may require wall stitching or underpinning.
• Severe cracking needs a professional assessment and possible foundation remediation.

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Are you concerned about cracks in your home?

If you have noticed cracks in your home and you are concerned, book an appointment with us now and we will inspect your house and offer solutions to provide you with peace of mind.

     Call  08 8223 3009

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