Poured concrete foundation exterior wear -- causes?

Specific Inspection Topics Structural Inspections
#1

I inspected a house that was built in the mid 1950s, which had a poured concrete foundation that looked great on the inside, with hardly even a typical crack, but had noticeable wear on the outside, especially opposite the driveway side, where there was a gravel surface between the house and the adjacent driveway.

There was hardly any loose or flaking material observed, so this did not appear to be an immediately serious condition, but I am curious about the causes.

Could this be due to the concrete having been poured while it was hardening, the worst areas having been poured last?

Or just a poor mix in general, the effects of accumulating snow, splashing rain, ice melter from the adjacent driveway, etc., having caused the noticeable wear on the outside, while the undisturbed surface inside remained intact?

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#2

That looks like a mix with too much water or poor curing that crazed. The location of the spalling is right where splash back would occur from water draining down the side. Ice melt would certainly increase it on the drive side.

#3

Don’t forget the snowblower piling up all that snow along the foundation… freeze/thaw cycling… etc as already mentioned.

#4

Appreciate the replies. The first thing that came to mind was all the snow (often with ice melt mixed in) piled up from clearing the adjacent driveway year after year. Same problem was not observed on the driveway side, from which snow was presumably cleared.

It stands to reason that slightly “soupy” mix and/or having precipitation (possibly even snow or sleet – this is Michigan after all) during the curing period would make the surface least resistant to such deterioration near the top.

#5

Forms not completely oiled b4 pour, concrete not properly vibrated.

#6

Freezing Rain and melting snow will seep through the top layer of the concrete, pooling underneath the paste layer of the concrete and over the years eventually come off in little pieces at a time.
Not in bad condition for a 1950 build.

Rock Salt forming Subflorescence when too much rock salt is used as de-icer on concrete, it will collect underneath the “creamed”, finished layer of concrete. This salt will crystallize, creating pressure on the top layer of concrete and leading to spalling.

#7

Either which way that foundation in the current condition is probably a lot stronger then the new foundations being poured now.

#8

Forms may not have been oiled and the pour may have been done in two parts… footing, then slab. I’ve seen this before.

Andrew Constantine
InspectPro Home Inspections
Fort Mill Home Inspections](http://inspectprohomeinspections.com/schedule-now/fort-mill-home-inspections/)

#9

Sounds like we have a whole lot of possibilities but do we have a consensus this is not a structural concern?

#10

Plain errosion with age from splashing water and/or freeze/thaw cycles.:slight_smile:

#11

It is plain erosion. Concrete does not stick to naturally polished creek gravel as well as crushed limestone. Creek gravel has better strength thou.

#12

Way back when, pouring concrete foundation with the old man, running out of concrete seemed to be a standard.
He would always tell me to start adding more six inch stones in the wall to make up the difference. :mrgreen:

Riverwashed gravel from the St. John River between Maine and Canada was the perfect ingrediant for concrete in the 60’s until it was banned.
Now it has to be washed crushed stone which has more strength due to the cement past adhesion as James mentioned.

Damn, I’m older than that old man now. ;):slight_smile:

#13

I agree…