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Cracks Appearing

Cracks appearing

Q Cracks have developed along the walls of our conservatory where it’s adjoined to the house. The wall of the conservatory is approximately 6ft long and the other two sides have walls approximately 2ft long. The floor appears to have shifted because when we looked under the floorboards, it looks like the concrete floor has sunk by 2cm. Do you know why this is happening and what we can do to fix it?

A The occurrence of cracks or movement in your home can be a worry. There may be a number of possible causes and these all require examination. However, initially it should be determined if the cracking is affecting the structural stability of the wall/floor which would give rise to safety concerns.

Cracking and movement can occur as a result of general settlement after construction (slowly, over time), structural movement as a result of a failure (sudden failure), or cracking as a result of thermal movement, the natural expansion and contraction of a building structure.

I believe there are two issues that require further investigation. Firstly, the severity of cracking to the conservatory wall should be determined. This cracking may only occur to the plaster finish and not the structural block wall.

Subject to the level and extent of cracking to the wall/floor there may be a requirement to carry out on-going monitoring of the area to confirm that movement has ceased.

Light cracks (0-2mm wide) within the wall may not indicate a serious problem. Cracks up to 5mm are described as “slight” and can be easily repaired. For wider cracks it is advisable to seek professional advice. You indicate movement of 20mm (2cm) within the floor slab and this requires further investigation. This level of settlement can occur as a result of poorly compacted hardcore during construction. It would be important to determine if the slab has uniformly settled or if any fracturing has occurred.

When subsidence occurs to a structure it is normally abrupt and sudden as a result of a change in ground conditions. If the cracking and movement that you describe has occurred over a period of time, it is unlikely to be a subsidence issue. From what is described I believe that potential settlement has occurred within the concrete floor and to identify this you will need to confirm the date of construction of the conservatory to allow for an assessment on the level of movement that has occurred over a period of time.

It should also be established if there are any piped drains or a water supply running adjacent to or below the wall/floor, which may have been damaged or burst, causing soil erosion beneath the foundation causing it to fracture.

Subject to confirmation of the cause of movement, there are a number of repair options available. Repairs to the wall may require partial rebuilding or the insertion of metal support bars and re-plastering. Mini pilling could be required to the floor structure to prevent any further movement, with the application of a floor levelling compound to provide a level surface.

Andrew Ramsey is chairperson of the Building Surveying Professional Group of the Society of Chartered Surveyors Ireland. 

Read the article on the Irish Times Property Clinic by clicking here