Concrete Block Basements

What Are Concrete Block Basements ? Call 586-703-0112

We have been writing on most of my other pages about poured concrete foundation, but this time we’re going to talk about concrete block foundations. Also known as Cinder block foundation have their own set of problems. Back when I was much younger (and I won’t say when that was), concrete blocks used to be called cinder blocks. Cinder blocks were made from scrap bits of material from steel foundries. The foundries wanted to get rid of this excess material, and a good way to get rid of it was to encase it in concrete. The mixture of cinders and concrete was pretty strong, so cinder block foundations were tough enough to last.

Back around the Civil War when the country was only 75 years old, house builders would use what was readily available for foundations. That was what they call fieldstone. Fieldstone is nothing more than boulders or small rocks taken from the fields for use as a fieldstone foundation construction material.

Most often, back then, you wouldn’t find a basement or a crawl space, but a hole dug under the house used to store home-canned goods. These spaces, which maintained a steady, cool temperature, were ideal. They were commonly called “root cellars.” My great-grandmother had one, and it was pretty spooky. It was dark, damp and chilly. I remember she had some shelves down there, and on the shelves were canned fruit and canned vegetables.

I was pretty young back in the day, and don’t remember what kind of walls there were down there, to hold dirt back. Walls in root cellars were generally either boards or field stones.

Many people used fieldstone foundations. They would dig a hole in the ground, make a flat bottom, and lay the field stones on top of the dirt, with no footing underneath them. They stacked the stones until they got about 15 inches above the soil elevation. These so-called basements were just dirt floors and rocks that were mortared together, and the foundation of the house was just that, rocks. In this business, one of the problems I’ve seen in these older houses, is that the rocks were not interlocking at all. That meant that if the ground shifted at all, even a little bit, the walls would come apart. They could cave-in or shift, or do all kinds of weird things. They would especially leak water through the joints of the mortar, since mortar doesn’t stick well
to rocks and stones, long-term.

The basement I-beam, which supported the main floor of the house, was usually made out of wood 2 by 8’s or smaller like 2 by 4’s. In the dark, damp, cellars and crawl spaces, these wooden beams would often be eaten by carpenter ants, and softened by mold or mildew. Many years later stones came to be replaced by the above mentioned cinderblocks. Mortar stuck to cinder blocks much better than to the smooth-surfaced rocks. Cinder blocks issued in the genuine basement. Dirt floors began to be replaced with cement. Basements were not very tall, though; usually about 7 feet or under. So it was still a long ways from a perfect system.

Cinderblocks, or concrete blocks, are hollow. These are mortared together, stacked on top of one another. The holes all line up from top to bottom. So, basically, a concrete block wall is hollow. The pressure on the walls from dirt pushing in on the block wall, frost, vibration, or settling would cause microscopic cracks to develop on the wall. Generally, very little damp proofing is put on the outside of the wall. Thus, outside water would leak into these little cracks. With many little cracks, that hollow wall will become filled with water. In some basements with unpainted walls, you can see how high the water has been inside the webbing, usually by the damage on the inside of the wall, in the living area. Paint, or just any finish would be damaged to the point where you can see that there has been water.

The average basement has something like 125 lineal feet of wall, and we have seen the water as high up as 5 feet inside the hollow concrete blocks. On a 10- inch thick block wall, that’s a lot of water. We have gotten hundreds of gallons of water out of concrete block foundations. That is the big difference between the old concrete block walls and the newer poured concrete walls. Poured concrete walls seem to pass the water through immediately to the inside through cracks and holes. There is trapped water in the webbing. A concrete block wall holds the water like an aquarium, and seeps back through the block.

A lot of people ask me if we can inject foam to seal off the inside of the concrete blocks. That’s not practical, and really does not work. If the water is 5 feet high inside the wall, there is going to be a great amount of water pressure pushing on the wall.

These can be difficult cases to diagnose. It is always best to call us so we can come out and take a good look at what’s going on and let you know I how l would fix it, and what it costs. Call us at 586-703-0112 and set up an appointment.

This is a YouTube file and they host their own and use flash files that are less quality but much faster loading. This job was a concrete block job and it was also a flood damage job. It was done for a absentee owner in California. It included the wall and trim and drywall work as well.

Call Oakbridge Waterproofing for a free estimate 586-703-0112 .

Author: Robert B McGuire