Cracks and how to handle them

Don’t Panic when your house cracks!


Most homes develop cracks. Old and new homes can develop cracks as well depending on climatic and physical factors.

However, it is worth getting to the bottom of what is causing the cracking. A crack is actually the visible symptom of a possible problem and not the problem in itself.

What causes cracks?

New homes

In new homes, settlement may cause minor cracks. Normal foundation settlement occurs when the underlying soil compacts as a result of construction on previously undisturbed soil, changes in soil conditions and moisture. Typically small, hairline-sized cracking may be the result of a minor settlement, expansion and contraction, or changes in a season or cycle.

Usually, these defects, though often unsightly, are not structurally significant.

Thermal movements between different materials

Different materials such as timber, bricks, steel, concrete etc. have different coefficients of linear expansion. In other words, the differing materials contract and expand differently. This causes stresses in structures where they are combined and may cause cracks to form. The best way to combat these defects in plasterwork is to provide a joint between the different materials.

Older homes

In older homes, changes in climatic conditions can affect the structure. Houses move with the climate. Heat and moisture will make them expand, and cold and dryness will make them contract slightly. This movement is normal and in most cases will not cause cracking. Unusually hot or cold spells can result in increased expansion or contraction of the structure which may cause cracks.

The rise or fall of the water table in very dry or very wet conditions can also affect the house’s foundations.

Changes in the house’s surroundings, such as the placing of new gardens or the planting and growth of trees, can change the moisture content of the soil supporting the foundation.

The leaking of old water or sewer pipes in the ground can go unnoticed and change the moisture content of the soil under the floor and foundations causing subsidence of the foundation and filling material under floor slabs. Similar problems can result from leaking showers and baths.

Dripping hose taps and dripping water pressure regulators near foundations and irrigation systems spraying onto your walls and foundation can cause foundation subsidence and cracks.

The pooling of rainwater around your house or close to foundations will also affect your house’s foundations. Make sure the ground slopes away from the foundation.

Additions to the home such as newly paved areas and new rooms can also affect the moisture content of the soil. Older parts of the home’s foundation can be affected.

Vibrations from traffic or blasting, particularly if your house is over a ridge, can cause cracking.

Homes built above former mine workings, landfills and other possibly mobile ground can be most susceptible to structural problems.

There are so many more reasons that may affect the foundations of a home. Always try and look for the reason that a crack develops. Be careful about what you change around your home!

How to deal with cracks?

Plaster cracks

Where cracks are superficial, treat them with good-quality fillers and paints. Simply redecorating should be enough to mask most superficial cracking in plasterwork.

Most hardware and building materials stores sell fillers and paint filler combinations, which will help to repair smooth surfaces.

Structural cracks

Cracks in brickwork are a different matter. Climatic conditions acting on flaws within the brick can cause cracks. They can also be caused by any of the reasons mentioned before.

Look out for cracking around window and door frames. This may be symptomatic of extra stress being placed on the structure.

If doors begin to suddenly stick there may be a serious underlying cause. This is especially so if they begin to stick when opened.

Plastered brickwork

If the crack has resulted from a movement which may continue, you should reinforce the wall across the defective area. Remove the plaster approximately 75 to 150 mm on each side of the crack and remove all debris and dust. Nail a strip of expanded metal or chicken mesh, the width of the area, to the wall and wet it. Force the plaster into the area and work it to match the surrounding plastered area. Allow a drying period to repaint the wall corner to corner.

Face or semi-face brickwork

Cracks in face-brick walls pose a different challenge! Here you will need to remove the mortar joints across the crack for about 50mm deep and between 150mm and 200mm on either side. You then drill holes another 50mm deep one on each side and insert epoxy and a reinforcing bar with the ends bent up in a U shape into the holes. You then repoint the joints with mortar.

Alternatively, you can remove the brickwork around the crack and re-instate the brickwork if you can find the same or similar face bricks.

If you find an external crack in your walls and you leave it, the defect is going to get worse. Furthermore, water is going to use the crack as a way to get into your house.

To avoid future or further damage repair all cracks that are letting water in or are exposed to moisture.

If a crack suddenly forms that is more than 5 mm in width, it needs immediate professional attention. In addition, you need to find and fix the reason behind the cause of the defect!

Finally, before you buy a house, ensure you have commissioned a home inspection for possible problems.

Prevention is better than trying to find a cure.

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