As a home inspector in Orange County and while doing home inspections in Los Angeles and home inspections in San Diego it’s almost inevitable that when walking through the garage the buyer will point to a crack in the garage floor concrete and say, ‘what about that’ while pointing at the crack, or they’ll say, ‘should I worry about that crack?’

Well, do concrete cracks matter? They do in some areas sometimes. The structural wood frame of a slab built home is not resting on the slab though, it’s resting on the ‘stem wall’. The stem wall is shaped like an upside down T that is 12” wide at the bottom for a one-story house and 15” wide for a two story home. It is 24” deep. This upside down T is what your walls are resting on. After the stem wall footing is poured the concrete contractor pours the floors inside of the walls. This concrete is a minimum of 3 ½ “ thick, sometimes thicker. If you see cracks on the interior floors and cracks on the garage floor it doesn’t necessarily mean you have foundation problems. 

The dirt pad that your home is built on will move constantly. It moves for several reasons and sometimes it moves too much due an abundance of water retention. That is why drainage is so important around the perimeter of your home.

When I do a home inspection I always examine the perimeter to see if the stem wall has any large active cracks.  When I see cracks in the floor, unless there is an inordinate amount of cracking I don’t say the foundation is bad.

On an older home you’ll usually see more cracking but don’t get to worked up about concrete cracks because concrete almost always cracks.

Just make sure the home inspector that you use is knowledgeable about concrete foundations. I’ve been doing concrete inspections for over 12 years and I can spot a problem when I see it but usually it’s just normal concrete cracking.