What is the difference between a crack and a hairline crack?

Is this crack dangerous? Is it a crack or a hairline crack?

Unfortunately, it is common for the new owners of new-build homes to notice small cracks or hairline cracks in their properties and to wonder, with concern, whether they could be dangerous. To answer this, it is important to know the difference between the two:

First, a hairline crack is a surface opening of less than 1 mm (normally 0.5 mm), looking like a “hair” on the wall, which has not broken the brickwork, only its surface. It may be due to the thermal expansion of materials, to poorly applied render or to some other cause, but it does not affect the structure, only the appearance of the home. It usually runs horizontally and parallel to door and window frames and to floor slabs. Once they have appeared, hairline cracks do not move any further.

A crack, on the other hand, is wider, from 1 mm to 5 mm, and deeper, and may have split the brick or the tile, and may even go right through (so that it can be seen from the other side of the wall). The problem is that the crack may be a symptom of serious structural damage that can affect the safety and stability of the building. It usually runs diagonally (perpendicular to the direction of the pressure), in a zigzag (stepped pattern) or vertically with some kind of branching.

To determine how serious the cracks are, you need to know whether they are stabilised or not, which is why it is best to monitor how they develop. To check whether the cracks are still growing and moving, a technician should fit crack monitors across them and observe their progress over time.

How can you tell whether a crack is dangerous?

An expert architect specialising in building defects should determine how serious and significant they are, as well as the most suitable repair proposal and its cost. In very serious cases, they may even recommend installing props or evacuating the building.

If in doubt, it is best to contact us, DPcon S.L. Our experts can check how serious the cracks are and, where appropriate, claim repairs or compensation from those responsible.