05/02/2014
Subsidence
Subsidence is the downward movement of the ground supporting the building, the foundations of the house/building. Subsidence generally occurs in a structure when the ground bearing the structure yields, under the weight of the structure, and compresses to such an extent that the structure settles at the point of failure.
First obvious signs are the appearance of cracks - small diagonal cracks in plaster work. Cracks generally occur at weak points such as around doors and windows. Many cracks are innocent, but if they are wider at the top than the bottom, this may indicate a problem. These cracks may, but not necessarily, indicate movement of the foundations. Doors and windows may also stick due to the distortion of the building. Subisdence may occur progessively over a period or it may occur over a very short period and then stop.
Subsidence is usually caused by -
Leaking drains - damaged drains can soften or wash away the ground beneath the foundations.
Certain soils - clay soils are particularly vulnerable as they shrink and swell according to the moisture content.
Vegetation - trees and shrubs suck the moisture from clay soil and cause it to shrink.
The water which has escaped from the drains will not only erode the soil by washing away fines, but will also erode the limestone bedrock. This type of erosion is particularly common in the greater Cork area due mainly to the make up of the soils and the limestone bedrock in the area.
A simple hydrostatic test carried out on the sewers will determine if they are leaking. Digging a trial hole exposing the soil at the foundation line will facilitate an assesment of the soil to determine whether it has softened or not.
To stop subisdence it is generally necessary to underpin the house. The type of underpinning required will depend on the soil present and the existing foundations, and should only be specified by a suitably qualified engineer.
Work on a house will usually take two to three weeks to complete - 12 to 15 working days.
If you have any concerns about your property contact us.
Piling and beams
Piling and beams
Steel Bars underpinning
Underpinning in the hallway