Slab on Grade

Slab on Grade

This residence has a slab foundation. Such foundations vary considerably from older ones that have no moisture barrier under them and no reinforcing steel within them to newer ones that have both. My inspection of slab foundations conforms to industry standards, which is that of a generalist and not a specialist. I check the visible portion of the stem walls on the outside for any evidence of significant cracks or structural deformation, but I do not move furniture or lift carpeting and padding to look for cracks or moisture penetration, and I do not use any of the specialized devices that are used to establish relative elevations and confirm differential movement. Significantly, many slabs are built or move out of level, but the average person may not become aware of this until there is a difference of more than one inch in twenty feet, which most authorities regard as being tolerable.

Many slabs are found to contain cracks when the carpet and padding are removed, including some that contour the edge and can be quite wide. They typically result from shrinkage and usually have little structural significance. However, there is no absolute standard for evaluating cracks, and those that are less than 1/4" and which exhibit no significant vertical or horizontal displacement are generally not regarded as being significant. Although they typically do result from common shrinkage, they can also be caused by a deficient mixture of concrete, deterioration through time, seismic activity, adverse soil conditions, and poor drainage, and if they are not sealed they can allow moisture to enter a residence, and particularly if the residence is surcharged by a hill or even a slope, or if downspouts discharge adjacent to the slab. However, in the absence of any major defects, I may not recommend that you consult with a foundation contractor, a structural engineer, or a geologist, but this should not deter you from seeking the opinion of any such expert.

Certified inspectors are not structural engineers and cannot comment on the integrity of foundations, footings, slabs, etc.