Wednesday, June 16, 2010

Foundation repairs

Here are a few pictures of the foundation problems we discovered in the house after we were able to rip down some of the walls in the basement. These and some other problems are what conviced us to build new rather than renovate. While anything can be fixed for a price, it was hard to justify the cost of these repairs while still ending up with a seven foot basement and a sloping floor.

In the image below, this crack was directly beneath a window. The wall did not have enough strength to hold back the force of the ground on the other side. To fix it would have required pulling out the window and pouring a new concrete sill heavily reinforced with steel, which would prevent the wall from buckling in. The cost was estimated to be as high as $5000.

In the two images below, a large crack (about 1" wide) can be seen running down the wall from the ceiling to the floor. Amazingly, the basement window is also bent, but the glass is not broken.

The image below is from the garage, where frost has made its way under the insufficiently insulated floor. It's hard to tell from the photo, but this whole section of wall is buckling inwards due to the uplift of the floor and the force of the ground on the other side of the wall pushing in. To fix it would require supporting the house above while the entire wall is ripped out and rebuilt. The cost for this repair alone was estimated at $15,000 - $20,000

It was interesting to hear from our builder some of the history of these types of cinder-block foundations. Apparently, when these houses were built in the '50s, poured concrete foundations were available, but were more expensive and required a trained crew. A builder could save some money by using cinder blocks because the blocks were cheaper than the equivalent volume of poured concrete and the builder's own workment could usually do the job.

Interestingly, today the situation is reversed and it would now cost more to build a cinder-block foundation (not that I think you ever would want to).


  1. Wow, very interesting info about poured concrete vs. cinderblocks. What an expense to have these things repaird.

  2. Yes indeed, the cost of fixing foundations is quite high.

    Cinder block walls have great compression strength, so they are more than capable of holding the house above, but have limited tensile strength and are more prone to cracking and heaving if the house shifts or the frost expands outside the walls.

  3. I own an older home with a block foundation and some of the blocks are actually shifting. A couple of them have move either inward or outward two to three inches, and the water is coming in around them. Is this a common problem and is there a quick fix?

  4. Thanks for your comment. The builder we were originally working with told us that it is very common for cracks to appear in a block foundation. He said it is because lots of houses settle slightly in the first year and as they shift, the walls crack. However, he also said it is not necessarily a problem. If there is proper weeping tile at the footings, if there is a membrane outside the wall and if the grading of the ground outside slopes away from the wall, it is still possible that water will not leak into the basement. Afterall, Mike Holmes says that even poured concrete walls are somewhat porous and water will seep through without the proper waterprofing mechanisms outside. Our builder told us that a block wall with small cracks is not usually a problem with respect to its ability to hold up the house above, as cinder blocks have pretty good compression strength, and even with cracks the house won't fall down.

    Still, that said, if you have blocks that have moved inwards or outwards by 2 or 3 inches, that sounds like a much bigger problem.

    For small cracks, our builder told us that there are some simple solutions. One can inject a type of epoxy into the crack to seal it, or for larger cracks, one can inject a type of cement. That will seal the crack and as long as the house is not continuing to shift, that may fix the problem.

    However, to properly waterproof a basement, particularly one where the wall has shifted, there does not appear to be many quick fixes.
    In our case, with the wall buckling under the weight of the ground outside, the only solution to ensure a dry basement well into the future would have been to dig up the ground outside the basement wall, replace the sections of wall that were buckling inwards with a reinforced wall that could sustain the force, put in place weeping tile and platon membrane around the wall, and then backfill with appropriate material that can drain easily. Furthermore, in the case of our garage, which was being pushed upwards by frost each year because the floor of the garage was not below the frost line, it would have been necessary to lay insulation at the footings out to about 5 feet from the wall in order to stop the frost from forming under the garage in winter. Needless to say, this was not a cheap option.

    Eventually, we decided to tear the house down and build a new one. After we tore it down, we discovered that the house had been built on peat and hence was not stable, It would have likely continued to crack even after we fixed it.

    If I were you, I would ask a couple of different contractors to come by and look at it and suggest some options. You do not have to commit to work with them it it proves to be too expensive.

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