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May 2015

Question

In 2006, I built a four-bedroom house and was informed by the buildersthat as the property settles some cracking would occur. Cracking did start to appear over some windows, doors and ceilings. Over the years I havefilled in these cracks, but they always reappear. The house is on an incline and I recently noticed a small hole under the property. Is the problem subsidence? If so, what steps should I take to resolve this?

 

Answer

All buildings settle under their own weight and this can result in cracking. Settlement cracking happens at weak points in the structure such as at the openings formed by windows and doors. Generally this “bedding down” should be over within the first ten years.

Your house is approaching its 10th anniversary. At this stage initial settlement should have ceased.

Expansion and contraction of building materials as they age will continue beyond this general timeframe. Movement can also happen as buildings expand when heated by the sun and then contract when temperatures fall. This is known as thermal movement. It is common for houses to be constructed without joints that make provision for thermal movement. In the absence of these joints, settlement cracks can accommodate this normal thermal movement. This explains why filled cracks typically reappear. The building is simply expanding and contracting along the line of the settlement crack.

The sloping site you mention can leave properties prone to “differential settlement”, meaning some parts of the structure settle more than others. This should not be significant.

Subsidence is different. In cases of subsidence cracking occurs when the ground that supports the structure moves away or is eroded and support lost. This can happen if a water main or drain leaks and erodes the earth below the structure.

You mention you noticed a hole below the property. On the basis there appears to be some erosion, I suggest you engage a chartered building surveyor or other suitably qualified professional to inspect and monitor the situation.

It would be very important to differentiate between settlement and subsidence as repair methods would be different. Repairs to subsidence may be covered by your home insurance if the house is not covered by a builder’s ten-year warranty.

All buildings settle and crack and therefore I would not be unduly worried about cracks in buildings. However, as there appears to be some movement of the ground in this case, the matter should be investigated and the cause established.

Noel Larkin is a member of the Building Surveying Professional Group of the Society of Chartered Surveyors Ireland (MediKids)