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Addition problems: the foundation

Several times when I have mentioned our intention to tear down and rebuild our family room addition. I have also been told that we will at least save money if we use the existing foundation. However, the foundation is a big reason why we want to replace the existing addition with completely new construction.


The addition as it stands now violates the setback requirements from the road and the neighboring property.  We could approach our local building department and ask for “relief” to allow these encroachments and in normal circumstances we might be granted the required variances.  However, if the inspector was to take a closer look at the addition, he would likely issue numerous work orders to bring the structure up to code.  It will be much easier and less stressful to go before the powers-that-be and ask for permits for a new, properly built addition.  We will be still be asking for a variance for detached garage, but downsizing the addition itself.

Who designed this thing?

The addition sits on a block foundation with a crawl space.  A solid foundation supports approximately 80% of the addition, while the back wall is rests on a couple of single block columns.

foundation diagram
Foundation diagram.

The black lines represent the original house.  The red lines represent the foundation for the addition. 

foundation piers
Single column of blocks do not a strong foundation make.

It is a mystery why the previous owner or his builder chose to build the foundation this way rather than support the entire addition with a solid structure.

Another mystery is what he was thinking when he located the dryer vent in the middle of the solid wall. 

dryer vent
The dryer vent in the open crawl space.

The vent exhausts warm moist air into a cold zone under the floor boards. What could possibly go wrong?

The foundation wall has no other openings so the enclosed crawl space is completely inaccessible.   At least to humans. We also don’t know the depth of the foundation at this time.  Given how sturdy those piers look, I would be afraid to dig around them.

Structure and Drainage

Meanwhile, in the front corner where the addition meets the original house, a wooden porch concealed a host of issues.  Ignore the siding which was installed after the porch.  I’ll talk about that in a future post.

drainage and structual issues
The front corner of the house.
  1. The downspout originally fed into “Big O” drainage tile and we had significant water leaking into the basement.  The situation improved when I disconnected the downspout and extended it out towards the front yard.
  2. We have no idea where this other “Big O” goes once it passes through the foundation.
  3. Most troublesome is the separation between the new and new foundations. This is a possible point of entry for pests (we do have to deal with mice on a regular basis) and, during heavy rains, we have a mini waterfall in the basement.  You can see where I filled the crack with spray foam, but that isn’t really doing anything.
basement issues

The addition has a small stairway going to the basement of the original house where the previous owner cut a hole in the old foundation wall. During heavy rains, we have a waterfall originating from under the step. This is no longer an exterior wall and is about nine feet from the front corner. That means that there is a LOT of water getting under the addition.

Recognizing the problems

So, why did we buy this house when there were so many obvious problems with the addition?  The fact is that the problems were not so obvious.

  • The front corner was hidden by a wood porch.  Until we removed the porch, we did not know that the new foundation was separating from the old one, and we could not see where the “Big O” was routed.
  • Inside, there was another step in front of the “waterfall” step that was as long as the wall.  That helped to contain any water that came into the basement at that point.  We also bought the house in the winter when the ground was still frozen, so there was no chance of water infiltration at that time.
  • The piers at the back of the house should have been obvious.  That was something our inspector should have noticed.  He made a point of telling us to staple up some house wrap under the floor joists, yet he failed to point out any deficiencies in the rest of the structure.  This is a point where I regret not getting a proper inspection with a full written report (see Mistake #2 of Four mistakes that cost us over a hundred grand) .

Repairing the foundation

Let’s ignore for now that the footprint of the addition violates the setbacks required by our municipality. Can we actually save the addition, and is it worth saving?

The answer to the first question is probably yes. There are a number of solutions available to repair, underpin, reinforce and waterproof foundations. It might even be possible to jack up the addition and build a completely new foundation under it. While I have not explored all these options in relation to our foundation, I believe that tearing down and rebuilding the entire addition would be a better investment. To me, it makes more sense to start over and do things the right way, rather than try to fix what is already here.

Other posts in this series:

Poor Workmanship in the Addition

Electrical Issues in the Addition