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    Cracks in My Masonry Walls – Help Me!

    27 Apr, 2017 | 1,458 views

    Every week we get numerous calls from property owners worried about cracks in their walls. Here is some simple guidance which may assist you.

    When reviewing cracks, the width of the crack often takes precedence over the length of the crack.

    Category 1     Small (Minor) Cracks

    Includes hairline cracks <.1 mm and fine cracks <1 mm including cornice cracks (Tip: The nib of a Bic ball-point pen will not fit into the gap)


    The primary contributory cause is often settlement of the walls onto the foundations or movement in the building associated with changes in temperature and or moisture.

    Impact and repair

    It is unlikely that small cracks require any specific repair as the issues are more often than not cosmetic. If required, a process of patch and paint is the easiest solution.

    Category 2     Medium Cracks

    Includes cracks from 1 mm to 5 mm

    (Tip: The nib and potentially a part of the pen case of a Bic ball-point pen will fit into the crack)


    Whilst aesthetically concerning, cracks up to 5 mm can generally be patched and painted.   In newer homes the cracking almost inevitably relates to settlement and or vibratory action from within or adjacent properties. With older properties it can be the onset of one of the key contributing factors associated with Category 3 cracking.

    In addition, one of the major contributors to wall cracking is when downpipes are not connected to soak wells, the concentration of water around the footings at the downpipe positions can lead to subsidence of the footings and cracking of the house walls.

    Impact and repair

    Cracks within this category, as a general rule, can be patched and painted. However, the key issue is to determine significant changes over a relatively short period of time, say 6 – 12 months or even shorter. If the cracking gets worse, preventative action may need to be taken sooner rather than.

    One of the key issues is to determine whether or not there are any significant contributory causes to the cracking and whether or not preventative action needs to be taken immediately. For example, if there are rusting lintels or significant cracking to concrete which is facilitating water ingress, the cracking may only be minor now but unless the underlying issue is addressed it will only get worse. In short, often the remediation requirements of the contributory cause are often more important than the crack itself.

    The second major item is monitoring changes over time. Once you are aware of a crack, constantly looking at it will often lead to the perception that the crack is getting larger. Digital photography can assist greatly. Using your smart phone or digital camera (ensuring the date stamp is turned on) take regular pictures of the cracking to monitor changes. (TIP: Taking pictures of a crack on a white wall can be meaningless. Get somebody to place a coin in the picture alongside the crack as a point of reference, or use a ruler to show the width. This will assist in determining if the crack is static or growing.)

    Category 3     Large (Moderate to Severe)

    Includes cracks from 5 mm to 25 mm

    (Tip: A Bic ball-point pen or even a crayon will fit into the crack)


    These cracks are becoming significant and there can be a range of issues which are contributing to the cracking. The types of issues which can cause severe cracking include:

    • Issues with footings and or concrete pads (subsidence)
    • Water ingress, moisture/damp in the walls
    • Concrete cancer and rusting lintels
    • Impact damage
    • Issues associated with the roof frame or other load bearing problems
    • Concentration of water around the footings

    Impact and repair

    Cracks within this category, as a general rule, cannot be left untreated. At the smaller end of the spectrum, the crack will need to be filled so as to avoid any potential water ingress, particularly if it is an external wall. At the other end of the spectrum, the wall may need to be inspected by a structural engineer to determine what remediation work is required, the may even require a section of a wall to be rebuilt. Generally, and at a minimum, a plan of action needs to be determined and acted upon as soon as possible.

    There are Australian Standards which provide guidance and support when dealing with cracked walls, ceilings and floors. Australian Standard 2870 along with Guides to Australian Standards and Tolerances.

    Where to from here?

    During the maintenance period of a new home, Builders will generally repair all cracks. Beyond the maintenance period, unless a construction defect can be determined, it will generally fall back to the property owner to repair and maintain small and medium cracks. Patch, paint and monitor being the primary responses as well as looking for contributory causes.

    Properties less than 6 years old should not have large cracks unless an external force has been applied. As a general rule, builders in WA will return and repair large cracks during the 6 year defects liability period (where they are construction related) along with resolving any construction related contributory causes.

    Beyond 6 years, resolution of cracking will generally be the responsibility to the property owner.   Take these key steps:

    1. Small cracks (category 1) – patch and paint. Monitor for changes or consistent repeat cracking
    2. Medium cracks (category 2) – patch and paint but critically monitor changes closely and look for contributory causes. Addressing the contributory cause can be more important than the immediate crack.
    3. Large cracks (category 3) – Act now. Something may be occurring but doing nothing is not the best policy. Source or cause of the cracking needs to be determined along with a remediation plan for the actual cracking. Seek independent advice from a Registered Builder or Structural Engineer.

    Repairing Cracks

    The following procedures are recommended by a reputable paint manufacture:

    1. Hairline cracks  – Squeeze a narrow line of acrylic sealant directly over the crack then mould into the gap with a moist finger. The sealant remains flexible while keeping the crack hidden.
    2. Medium cracks – Use plasterboard patching cement. First dampen the crack with a brush dipped in water to allow the compound to dry gradually. Next undercut the edges of the crack so the compound is keyed in, and then follow the package instructions on when to paint.
    3. Joins Between Different Materials – For gaps where two materials join such as around door frames, architraves, cornices and skirting boards you will need a flexible sealant. Choose one that is easy to apply and is paintable, durable and cleans up in water.

    The patched areas can then be painted following the recommendations of the paint manufacturer.

    How can Houspect WA Help?

    If you are worried about cracking on your walls, call Houspect WA to discuss your concerns.  It may just be a matter of classifying the cracks and developing a plan to monitor and respond if the position changes over a short period of time. Alternatively, it might be appropriate to have one of our Building Inspectors (all of whom are WA Registered Builders) inspect your home to confirm the crack category and more importantly any identifiable contributing factors which may need to be addressed. Where appropriate, we may direct you immediately to a structural engineer to assist.

    Contact Houspect WA 9240 8855 or  https://www.houspect.com.au/wa/


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