Structural Integrity, Structural Failure & Slab on Ground Foundations
Structural integrity is an aspect of structural engineering which deals with the ability of a structure or a load-bearing structural component to support design loads without breaking, tearing apart, or collapsing.
Structural integrity is the ability of a structural member to hold together under a load, including its own weight, resisting breakage or bending.
The intent of designing structure to maintain structural integrity is to ensure that catastrophic failure does not occur, which can result in injuries, severe damage, death, and/or monetary losses.
Structural integrity as related to foundation performance
It would be extremely unusual for a modern steel reinforced concrete slab-on-ground foundation to exhibit a structural integrity problem. There was a time when codes for residential foundations did not require reinforcing steel to be used in slab on ground construction. That day is long past. Modern codes require conventional reinforcement, post-tensioning reinforcement or a combination in all slab-on-ground foundations where they are on expansive soils.
It would be extremely rare for a modern slab foundation to lose significant structural integrity. A still rare, but more likely loss of structural integrity, is where the foundation bends severely enough to pull the framing apart.
A related concept, structural failure, refers to a situation where the load-carrying capacity is exceeded in a component or member within a structure, or of the entire structure itself. Structural failure is initiated when the material is stressed beyond its strength limit, thus causing fracture or excessive deformations. In a well-designed system, a localized failure should not cause a sudden or a progressive collapse of the entire structure.
Structural failure as related to slab foundation performance
Structural failure of a slab-on-ground foundation is extremely rare. Consider this: the most obvious form of structural failure is where a structure collapses. Slab-on-ground foundations cannot fail in that sense: they are ground supported which means they are already on the ground. Collapse of a slab-on-ground foundation is physical impossibility.
Can slab-on-ground foundation movement cause a house to collapse? Another virtual impossibility.
Why you should not use the terms structural integrity and structural failure
Both of these terms are used by many people as sort of throw-away terms. They sound good and people have an idea what “integrity” means and what “failure” means, but when used regarding the slab foundation performance they are liekly t be misunderstood. Here is what I recommend that you do:
- The only way a slab foundation can loose structural integrity is for it to develop cracks where one side of the crack is higher or lower than, say, an eighth of a quarter inch. The width of the crack, not counting edge wear, should be at least an eighth or a quarter of an inch wide. I recommend that you just tell them that the width and diselevation are signs that the crack could be structural and that they should consult with a Structural Engineer.
- I would never use the word “fail” in discussing foundation performance. Your client is likely to conjure up images of the house collapsing or the foundation crumbling into dust. Just give them a carefully crafted independent opinion of how the foundation is performing.