Summary: SARL Dobson Structures recently surveyed a 1970s concrete block property built into a hill. Our assessment identified minor cracks and signs of natural movement, likely due to thermal expansion and soil shrinkage from nearby vegetation. We recommend targeted remediations—including render reapplication, crack monitoring, and soil stabilisation measures—to ensure long-term structural stability.
At SARL Dobson Structures, we recently completed a thorough structural survey of a 1970s concrete block property built into a hill, featuring multiple basement levels. Conducted on Tuesday 27th August 2024 by our experienced engineer, Ross Dobson, the survey focused on identifying visible defects and understanding the underlying causes of cracking and movement throughout the building.
Key Findings
External Observations:
Wall Cracking:
Hairline vertical and horizontal cracks were found around the property. In most areas, these are likely caused by natural thermal movements and the gradual expansion and contraction of mortar against concrete block construction. One area on the south-east elevation showed more significant render degradation, suggesting water infiltration has loosened the render from the blockwork.
Stepped Cracking:
Small stepped cracks were noted at the windows, rear door, and balcony sill. These may be linked to slight differential movement from soil shrinkage, possibly influenced by nearby oak trees and recent drought conditions.
Patio & Pool Movement:
The patio foundation shows a noticeable slope, and the pool area has cracking near service zones – both indicative of ground movement on clay soils.
Internal Observations:
Minor cracking was observed in several rooms, such as the living room and master bedroom, which appear to be typical for older properties and are likely due to seasonal thermal expansion and contraction.
Cracks in internal stud walls and tile finishes in the kitchen were also noted but do not currently raise significant structural concerns.
Basement & Sous-Sol Areas:
In the basement, certain cracks in blockwork walls hint at historic movement. One area in the lower ground floor shows moderate cracking that may require attention if further movement is detected.
In one of the sous-sol areas, there is evidence of ground movement that could impact structural stability. Here, we recommend urgent monitoring and, if necessary, remedial anchoring solutions to secure the affected area.
Proposed Remediations
Based on our survey, we recommend a proactive yet measured approach:
Render Removal & Reapplication:
Remove degraded render in areas with significant separation to assess the underlying blockwork and then reapply a suitable finish.
Monitoring Cracks:
Implement a monitoring programme using simple telltales or measurement markings to track any further movement, particularly in areas affected by soil shrinkage near oak trees.
Soil Stabilisation:
Should any critical cracks continue to propagate, consider a soil stabilisation approach – such as geopolymer injection – to mitigate further ground movement without extensive excavation.
Anchoring Solutions:
In sections where ground failure is visible, we advise the use of resin-fixed anchor bolts with steel plates to transfer loads securely into stable soil layers.
Concluding Remarks
The 1970s property shows evidence of minor, seasonal movements rather than major structural failures. Our recommendations focus on monitoring and preventative maintenance to ensure long-term stability. By addressing these issues now, we help safeguard the building’s future, providing peace of mind for the client and a solid foundation for any planned renovations.
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