Cinderblocks missing in two corners of my house

Question

I have a bilevel home with no basement that I recently purchased in Northern NJ. Property is on a flat lot. The house is 55 years old. I recently discovered that 2 corners of the home are missing cinderblocks. One corner also has a deep hole (2ft+) where the cinderblock was, which must been dug up by a critter. Is it possible that water from the gutters eroded those blocks? How to repair?

• The house has a cinderblock foundation wall that goes up about 3 feet of the wall.

Answer 1

Blocks can decay due to freeze cycles, impact damage, and other causes. It's not clear what the issue is here. I'd want to clear soil away and get a better look at the extent of the damage.

Individual blocks can be replaced using the same technique as when they were installed. You'd excavate the area, clean out any loose or degraded blocks and debris, then lay new blocks with appropriate mortar. It's certainly a job a motivated DIYer can do. I suggest viewing some YouTube videos on blocklaying to get a sense of how it's done. It's important that you create a solid mortar bed with no cavities.

Answer 2

There should NOT have been a cinder block supporting the structure of your home — if there had been one there previously it was not for that purpose. The concrete slab itself rests on the earth. Things like root systems and animals and, importantly, water will remove earth from the foundation, especially along the edges and by water downspouts, not to mention general water flow across the property.

Unless that entire corner of the house has sunk more than an inch or two you can consider yourself in very good shape for a 55 year old house in NJ.

Pack the hole as tightly as you can with earth.

And I do mean tightly. Use some kind of machine.
(And by “earth” I mean fill dirt.)

I do not recommend packing it with concrete or rocks or other blocks. They will not be sufficient to support the building and will contribute undue stress to the foundation.

If the building has sunk significantly your options are to simply do as above and leave it as-is or hire a company that specializes in fixing foundations, which is not cheap, but nevertheless very do-able.

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Because of the continuing questions about the foundation’s structure, I made a picture:

OP’s additional pictures show that his house is indeed sitting on a slab. The brickwork around the edges are not holding that slab up off the earth — they are helping to hold the fill dirt in place under the slab!

Everything moves. That’s why headstones in a graveyard are all crooked after a few years. You can think of your slab as a kind of giant surfboard on a slowly moving wave of dirt.

The fill dirt is packed to give a nice cushion for the weight of the home. Put something hard under it (different than the structure it was built on) and you have introduced a new stress on the slab that wasn’t there before. It may be some years before you see the damage, but it will happen.

^{⟶ It is the same reason trees planted right next to the house eventually crack the foundation. The root pushes it up, then water follows the root (or what’s left after the tree is removed/dies/whatever) and the foundation concrete can no longer properly support the weight of the house at that point and cracks.}

By putting the dirt under the home in essentially a box you help mitigate movement of the earth directly under the foundation.

For a bi-level building you have an additional issue: run-off water will eat the soil packed up against the front of the house. For my home we’ve had to patch or replace the porch and garden planter slabs twice now, and it needs it again.