Expert: Bruce E. Johnson - 7/26/2010

Question
QUESTION: Saw an answer to a question quite similar to my problem and hope you can help. I've talked to city inspectors, engineer and others with no help. Our house is on Marco Island Fl on a canal to the Gulf. House is 38 yrs old and never a problem with erosion. Plumbers replaced cast iron pipes under the house by digging under the house (by hand# and removing all they dug #never replacing it#. Since then we noticed considerable erosion around the entire house, some cracks in the walls %26 tiles. My husband went under the house #we tore up the bathtub and found an access hole) and the void under it is huge and he visually noticed a constant stream of water under the house from where the pool is. We weren't aware that the soil wasn't replaced until we did are own investigation but locals act as though it is no big deal. They claim many houses have had this done with no problems. We think the rapid erosion, cracks and even seawall sinkholes are a result of this. While under the house my husband noticed that they blew out a portion of the footing on one corner. My dad owned this house for 22 yrs before I bought it and I know it well along with the history. Why all the erosion suddenly now a problem. Please HELPPPPP us. T.J

ANSWER: Hi Toni, it sounds like they might have broke one of the pipes in the pool plumbing or possibly the lawn irrigation system and it is washing out the dirt.  It is also possible that they never did the work properly and your sewer is washing out the dirt.  It's hard to say just what is causing your problem without seeing it. A breach in your seawall will also cause erosion on built up canal lots.  Sinkholes are also a problem in Florida.  I'm surprised a geotechnical engineer can't figure out what is causing the problems.  It sounds to me though that your plumbers never backfilled the plumbing properly and they undermined your entire house.  They should have replaced the dirt and compacted it completely as they worked their way out from under the house.  It may have to be fixed similar to the way they fix sinkholes, grout may need to be pumped under your house to fill up the void left by the plumbers.  I hope this information helps please feel free to write again regarding this or other matters, sincerely bruce e johnson..

---------- FOLLOW-UP ----------

QUESTION: Bruce, Thanks for your quick response. I'm of the opinion that our problem is the void the plumbers left under the house which my husband says is approx. 4 ft high and 6 ft wide from one end of the house to about the middle and it gets smaller after that but continues to the other side. We think the void should've been filled too and the erosion around the house is from this void. City inspector and other construction people think it's fine because so many other houses had it done. My question is this. Who or what entity would approve this plumbing process of digging out under the house and replacing pipes and NOT replacing the soil/sand. Where would this fix have come from? Would the state have to approve this procedure.  They didn't just make it up, right? What about State Building codes?? You also mentioned a geotechnical engineer, is this the same as a structural engineer? Thanks again. Toni

Answer
Hi again Toni, basically the government agency that inspected your plumbing work only inspects the plumbing period.  It is your agreement with the plumber that should have spelled out the backfilling process. It is possible that the plumbing contractor excluded that from his contract and expected you to have someone else do the backfilling.  Look at your work documents and see just what is said regarding backfilling etc. and you will probably find the backfill excluded.  It is a bum deal for you and the contractor should have made it clear to you that the backfilling was your responsibility instead of just finishing the piping and leaving.  A geotechnical engineer deals with soil erosion problems, sinkholes and other ground related issues and is different from a structural P.E. although some may also be P.E.s.

You need to get this void filled and compacted as soon as possible if it is not too late already.  You could ruin your entire house foundation.  Check with your homeowner's insurance and see if they may cover some of the costs. I hope this information helps, please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com