Construction Consulting Questions #3 – What does it mean when I see a horizontal crack along my foundation?
September 10, 2009
Construction Consulting Questions #3 – What does it mean when I see a horizontal crack along my foundation?
The horizontal crack that most people refer to along a concrete foundation is usually located at the base of the wooden foundation sill plate which is attached (or should be attached) to the concrete foundation. A wooden cripple wall or floor framing system is normally built on top of the wooden sill plate. Throughout most of the 1900’s up until the 1980’s or so, when stucco was applied as the exterior surface to a structure, the stucco was often toweled on down past the sill plate so that it adhered to the exterior face of the concrete foundation.
Adhering the stucco to the outside face of the concrete foundation was a common practice that made the stucco look flat and uniform at the bottom instead of being formed in or shaped back toward the sill plate which would then cause a visual protrusion so to speak.
The horizontal crack that is referred to by most people is more often than not caused by foundation rotation. When the soil that the concrete foundation is placed upon becomes wetter on the exterior side of the foundation than the interior side, the soil gets compromised “softer if you will” and then the outside bottom portion of the concrete starts to settle relative to the inside bottom of the concrete, and the concrete foundation then begins to rotate outward. As this occurs, the bottom of the wooden wall above the sill plate also goes outward causing a horizontal crack which we are referring to. However, the crack, as you are now beginning to see, is not a crack in the foundation at all but rather the displacement between the stucco adhered to the wooden wall (at the base of the wall) and the stucco adhered to the exterior face of the concrete foundation.
Prime suspects for causing foundation rotation, which in turn can create the visual horizontal crack, usually start with poor exterior surface drainage. Land which slopes toward the structure then creates a low area along and adjacent to the concrete foundation itself. Surface water, as well as, “or in addition to” the rain water which drains down the siding of the structure can thus end up soaking the soil and compromising it to the point where the concrete foundation actually starts to rotate. So there you have it, foundation rotation being more often than not, the cause for the appearance of horizontal cracking along the foundation(s) of a structure.
Anderberg Construction Consulting, Inc.
4100-10 Redwood Road #368
Oakland, CA 94619-2363
(510) 482-2779
tomanderberg@gmail.com
Construction Consulting Questions #2 – Foundation Cracks – How do I know if they are significant?
August 26, 2009
Construction Consulting Questions #2 - Foundation Cracks – How do I know if they are significant?
For homeowners, to be told that you have cracks in your foundation, can really make you nervous. With most people being aware that their home is built on top of a concrete foundation, the notion that their concrete is cracking brings them to the question – How do I know if they are significant or not? How many answers would you like?
Since most concrete will crack (but not always), the best way to start analyzing the issues is to get a basic understanding of how cracks occur. Essentially there are two main sources of cracks, shrinkage (installation and curing methods) and stress (forces applied to the concrete after it has been installed). Cracks from installation are not necessarily detrimental to your structure but cracks due to stress can be. This is where “the rubber meets the road” so to speak. Are the cracks going to become larger? Are they a sign of ongoing issues which should be immediately addressed or do I have time to deal with them? Different opinions on what to do will be found in the advice you will get. Sound confusing? It can be.
Getting back to the question of how big does a crack have to be to really impact your home; I would say that if you can put your fingers and hand inside the crack, that would definitely be considered problematic and more than likely should be addressed as to its significance.
Smaller cracks from 1/16” to ½” can be readily found in the concrete foundations of many homes throughout the Oakland Hills and the Bay Area. Whether you live in the hills of the East Bay and San Francisco or the flatter areas in Contra Costa County, soil and ground conditions are typically the root cause for settlement issues which in turn can cause stress on the concrete. Sloping floors, cracks in walls, sticking doors etc. can be signs of possible concrete settlement which can also result in concrete cracking.
To determine the best approach to your concerns with regard to concrete foundation cracking, get experienced input from professionals. Most professionals fall into the categories of contractors, engineers and consultants. A moderate amount of time spent educating yourself by speaking with various people in the trades will hopefully help you with your decision process on what to do and how to proceed to the next step.
Anderberg Construction Consulting, Inc.
4100-10 Redwood Road #368
Oakland, CA 94619-2363
(510) 482-2779
tomanderberg@gmail.com
