It should be an old adage - water pressure - if what's below moves, what's above usually follows!
That's why when something utilizes something else as a foundation, the foundation should be strong! Hence the word ... foundation.
This is a 40 year old house, with a 15 year old addition. The addition is a large family room. It has a brick foundation, with a continuous-wall crawl space underneath.
The basement door of the original house used to exit to a stairwell.
They decided to enlarge that space with a retaining wall that extends to the foundation wall of the newer addition, and help frame the door way to get to the crawl space underneath that family room.
On one end the corner deck post rests on top of the retaining wall. That is a big no no. Retaining walls cannot also support a deck.
On the other end the retaining wall ties into the foundation wall of the family room addition.
Two different downspouts drain water into the area under the deck. Of course this puts pressure onto the retaining wall. It has not taken long for that retaining wall to respond to the water pressure.
It has bulged inward badly, cracking as it bulges. That is called "masonry bow and sweep."
That is a problem in itself. The bowing here is dramatic.
At the other end we have another problem.
Where the retaining wall ties into the foundation wall under the addition the moving retaining wall is pulling the foundation wall apart.
The crack there is 5 bricks wide and moving upward in a step fashion.
Being larger at the bottom than the top would indicate the movement of that foundation wall - toward the door.
You can even see the bowing in the frame of the doorway to the crawl space.
There is creaking in the hardwood flooring of the family room right at that point as well. Everything ties together!
One thing leads to another.
Eventually the SYSTEM falls apart.
Pressure will cause movement over time. What started with water draining into a framed area it cannot escape ends in utter disaster.
By the way, there is no door to that crawl space. It is always open for business. Really? No door?
What business do I mean?
The local mammalia!
The homeowners even have a trap in there to hopefully curb the Mammals R' Us! comings and goings!
Good luck with that!
That crawl space is a regular condo development.
My recommendation: additions have to be thought through carefully, particularly when they rise up off the ground. The word SYSTEM up there is intentional. A house is a SYSTEM of many things all working together. Their work can be harmonious or not, depending on how well thought out each component part is, and how well it plays with the rest of the stem. In this case this problem was virtually planned in advance. Houses cannot stand too much water pressure over time. Water, and water pressure, is the number one consideration outside when planning the footing/foundation situation. Too much pressure and time will ALWAYS work against a house. Eventually something will give.
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560