Uneven Floor Slab, Flawed Construction?

by John
(Manitoba, CA)

Question:

My wife and I purchased a condo in 2012. The den floor which is concrete on grade (no basement) is very uneven. We have had a concrete expert with 30 years experience tell us our issues are due to improper backfill. The builder and the New Home Warranty Program disagree and say it is based on clay and clay subsoil conditions.

We are experiencing a very uneven floor where a crack runs 12' from the wall in the utility room to the wall separating it from the den area. When you rub or flick the crack with your finger nail you can tell that one side of the cracked slab is higher than the other.

We have to shim our furniture that is situated 2' from the south wall. The shims are about 1/2" high. From the north wall when you walk in from the garage the slab dips almost 1" within 3' of the door. There is a closet for coats there that had a shim installed under the door guide at construction.

The shim is 1/2" thick and the door guide actually no longer holds the door in place as the slab has settled again. Do you have any documentation that states the symptoms listed above are due to improper backfill?

Answer:
Hi John,
Sorry to hear about what is happening to your condo. I can only imagine how tough it is to face this issue only 3 years in to ownership. The fact that the builder and home warranty are in the conversation tells me that your condo is new construction, and to face the problems you've described this early is a indication the construction was flawed. If the slab is having this problem this early, who knows what is going on with the footings which will lead to an unstable structure.

Let's assume the builder is correct in that the floor slab problems is caused by subsoil conditions. The subsoil conditions that can cause this has something to do with moisture that could come from high water table, broken water or sewer line, improper drainage. I would check with your neighbors to see if anyone else is facing the same problem. If the problem is strictly to your condo you need figure out where the water originates.

It is the responsibility of the builder/developer to do soil testing prior to construction. Soil testing is done by a geotechnical engineering company that extracts soil samples from construction site in order to come up with construction recommendations to avoid/minimize the exact problem you are having. If the issue is subsoil conditions, the builder should have known that prior to construction and should have built accordingly.

As for the improper backfill documentation you are asking, I would go right to the builder and ask for compaction report. When compaction is done, it is required (based on geotechnical engineering recommendations) to do compaction testing which should be monitored by the builder.

Due to the fact that soil behavior differs from location to location, soil testing and compaction from other location can't used in your particular location.

I would keep the heat on the builder asking for geotechnical report done on your site prior to construction. My guess is due to the cost, the geotechnical engineering testing was not done which was a risk took upon by the developer/builder. This is precisely the reason for liability insurance and your builder should have plenty of it.

I hope this helps.
Tonga