Langdale is a wonderful community right next to the BC Ferries terminal that connects the Sunshine Coast to West Vancouver. Many new buyers choose this location for their residences because of its proximity to the ferry, making it possible to walk-on and take public transit all the way to work in downtown Vancouver. The area has ocean-front, residential clusters, small acreages, and with pockets of commercial and industrial zoning.
On this particular acreage home inspection, cracks were noted in the floor of the attached garage. The buyer wanted to know if she should be concerned or not. Just after she asked the question we both heard a blast and felt the vibration from a not-so-nearby quarry. The next question from the client was whether the blasting in the area was creating the issue.
I thought about ‘crack theory’ and went through the options…
(1) Is it from concrete curing, a shrinkage crack with fine lines - no
(2) Is it from expanding soils, water freezes and increases in volume - not likely in this temperate zone
(3) Is it settlement from inadequate subsurface preparation or soil erosion - probably
The client and I then walked around the exposed three-sided perimeter of the attached garage. There were no mirroring cracks in the exterior foundations. A good sign. However the asphalt driveway immediately in front of the garage door had settled right at the contact point with the garage's concrete slab. As a result, rainwater was likely draining here, washing out some of the fill and undermining the slab. With a hollowing-out of fill, vehicle movement would flex the slab to it’s 'limits of elasticity' (engineer-speak), and beyond.
Now with respect to the quarry blasting. Since the operation was a few kilometers away, it was not likely to have any contribution to either crack development or propagation. If there really was an issue with blasting then there would be multiple complaints registered in the neighbourhood. This is where local knowledge by the realtor would corroborate the issue, if there was one.
The recommendation was made to have the settled asphalt area removed, missing fill replaced and the new surface installed with a slope away from the garage for good drainage.