Cracking in walls and ceilings is by far the most common issue our surveyors are asked about when they survey houses for potential buyers.
Understandably, people are worried that the cracks are a sign of structural instability or subsidence. Subsidence is the sinking of the ground below the property, resulting in damage to the foundations and movement of the walls and floors. This movement shows in cracking, and in severe cases can lead to instability and even collapse.
Fortunately, most cracking is cosmetic. It is often due to ageing and weathering of masonry or other building materials, and it’s fairly rare that it reflects any structural issues.
What to Look For
There is a lot to look for when viewing a house, with the structural condition of the property coming top of the list for many people. So how can you tell if a crack is something to worry about or simply cosmetic?
Cosmetic cracking: inside
Cosmetic cracks are usually dark in colour throughout, and the same width all the way along. They typically run straight up and down (vertical) or side to side (horizontal).
Minor cracks like these are normally caused by thermal activity – when materials heat up, they expand. When they inevitably cool again, the resulting shrinkage can cause minor cracking. This can be remedied by filling and redecorating.
Cracks around the junction between the wall and ceiling are a good example of interior cosmetic cracking. These are common, and rarely associated with foundation movement. Instead, they are usually caused by the plaster shrinking. This is normal and is why coving is often installed in these areas.
Regular-patterned cracking to the ceiling is similarly common. If it follows the lines of the plasterboard sheets it is unlikely to due to a structural problem – instead, it has probably been caused by reverberation of the floor above.
Cosmetic cracking: outside
Cracks in render are commonplace. Render is a hard material, so it almost always cracks over time because of the effects of heating and cooling.
Render cracks are not usually a sign of a structural problem; however, they do need to be addressed. When render develops small cracks, water enters and gets trapped. The only way for the moisture to escape is through the internal wall, which then results in patches of damp. In addition, if the water freezes before it escapes, it will expand, exacerbating the cracking.
The remedy for this is to keep the render in good condition, and regularly decorate the render with good quality, breathable paint.
Structural cracking
Cracks that are diagonal, or that look like a staircase, can be signs of structural movement. This is because the cracks are a result of rotational movement within the structure of the building.
Other signs that cracks are structural include widening throughout the length of the crack, and the crack being fresh in colour.
The extent of the cracking is also important. Essentially, the longer and wider the crack, the more likely there’s a significant issue.
Other warning signs
External factors can also provide clues as to whether a crack is likely to be a sign of something more serious.
For example, tree roots and leaking drains can alter the soil around a property, which in turn can damage the foundations. Therefore, cracks near large trees or drains should be carefully investigated.
Similarly, if your home is among the one in three UK properties that sit on a coal field, there is a chance that the property could be affected by ground instability and subsidence resulting from previous mining activity. Mortgage companies will often request a full structural survey by a chartered surveyor before agreeing to lend on such properties.
Other problems within the house can indicate that the cracks might be more than cosmetic. If the same property has issues with doors and windows sticking, or sloping floors, this can be an indication of structural problems.
What to do if you find a crack
Once some slight cracking is noted, it is important to regularly monitor it. A diagonal crack due to movement can be worrying, but if it is identified early and the cause of the movement fixed (e.g. replacing leaking drains, or controlling trees), it is very possible that the structure can be stabilised and there will be no further damage.
The key test is whether it worsens over time, because that shows it’s progressive. At this point, it’s recommended that a surveyor or structural engineer is appointed to assess it and advise on remedial works.
