House is Sinking

Hi Dr.,
I have a couple of questions. Our house is built on a slab. it is ranch house. For some reason on section of the house is separating form the rest. It is a brick house one story. We now have two large cracks in the walls in one room. I think that the slab may be sinking or has broken. The house is about 50 years old and I thought the sinking/settling would have already taken place by now. What should we do?

second:
Is there a way to put a second story on a house that sits on a slab?? what considerations do we have to take into account because there is no "foundation" I do not know the thickness of the slab.

Please help. Thanks, MP
Both questions require a structural/geotechnical engineer to review the conditions. In general, you are right about the expected stability in older houses. However, if it is built on very expansive soils, and soil moisture conditions changed, movement can happen. You may have heard about all the damage to houses in Southern California due to slope movement after excessive rains.  Movement can also happen if someone in your area is pumping water out of the ground close to your foundations, or natural ground water level changed for any reason.

You may also have to consider the remote possibility of structural failure in the foundations (if you have structural foundations) that can occur over time due to corrosion of steel or chemical attack on concrete.

Regardless, it sounds serious enough to require immediate investigation.

It is possible to add a second story. Any qualified engineer can calculate it easily based on the size of your footings and soil conditions. You may have to reinforce the footings or add some external supports, but it is not very difficult.

Good luck