house foundation failure

huangyhg

house foundation failure
a client has a house in florida built 35 years ago on a cypress head.  one section of the house has settled 5" with the accompanying cracks and distress in the tie beams, vertical walls and adjacent sidewalks and porch.  a cypress knee has grown 12" in a flower bed at the main entrance.  piers, grouting, demolition and replacement and other remedies have been suggested by contractors.  no soil analysis has been made on this structure, but a neighbor did have one and sinkholes were ruled out.the client will not report this to the insurance agent for various reasons.
the question:  anyone out there have design/construction  experience in this area they would like to share/
ok please excuse my lack of understanding, but what is a cyprus head? is it a cyprus tree stump?
reagrds
sc
sc,
cyprus head is not just a stump. it is huge and they can get very large with roots emanating from the trunk area outwards and they stay close to the surface.
cyprus trees thrive in wet and still water areas.
my question, how did they miss this stump? and how deep and large is it?
many issues come to mind. fixing this problem is not going to be cheap and repairing to insurance may not be avoided.
i also have a concern with the quality of the construction since the contactor covered up or built on the stump.
i suggest that competent engineer look into this situation, prepare a report aided by geotechnical analysis and feasible and proven repair method that will keep the structures integrity during and after the repair work is done.
good luck
thanks lutfi,
i agree it could not have been missed during construction or by a geotech as a major problem. now that the house is built it will provide problems for very long period of time. i don't believe that killing the monster is an option as this will lead to decomposition of the roots that are under the house. by the same token letting it continue to grow will also cause problems as it draws moisture from the ground.
as you need to get the point of bearing for the footings below the zone of influence by the root system. ie you need to get to a point of relatively stable moisture content. on the face of it piers would be the way to go, providing the existing footing system can be used with piers.
as lutfi said you really need to get a local structural engineer (pe) to look at it on site and to devise a method of repair.
regards
sc
thank you for the quick response.  this is the first time i have used eng-tips and it is impressive.  looks like a geotechnical analysis is the way to go; i'm getting prices of $6-10k for this service.  i'm probably going to go with something like soil nails.  anyone had experience with saber?
thanks again for sharing your expertise.
i believe whatever the solution it is going to be expensive.  i have experience of cutting down many trees over 50 years old and 50 ft high, with the stump approaching 300lb just below the ground.  the sure way is the remove the stump, with all its roots, because it will rot or decompose in time.  tree roots do sometime prop out shoots if they are not removed properly.
the problem appears to be the growing instead of the dying effect of the stump.  in such a case, simply drill holes and put tree poison into the exposed roots.  
if the foundation is grouted up sufficiently ( holes drilled at an angle below the foundation and cement grout injected) the effect of rotting tree stump can be mitigated.
care have to be exercised not to damage any services like drains, cables etc).  the injected grout simply help to spread the load over a bigger area with a hardened soil mass containging a potential big void.
bbird:
thanks for the imput.  some contractors have recommended replacement at a cost of $80-$100/sf.  one contractor gave the client an estimate of $40-$45k for a compination of grouting and pile support at the perimeter, with no guarantee against future failure.
so, it has become one of the classic engineering problems associated with constuction failures. your comment on the water and sanitary lines is appreciated;i'll have to have compentent contractors standing by.
for those of you watching this, i will give you some feedbck as the project develops.
i have had cypress head removed the were several tons.  single stumps have filled 16 cyd dump trucks.  
what i see as an the issue is typically the soils cypress are found, are black organic muck.  sounds like the site was not properly pepaired.  the florida building code prohibits building on organic matter.  the builder should be invoved with the remediation and desisions since he has liability exposure.
boo1:
you are absolutely right.  all signs point to no or little site preparation.  i will try to track the builder down.
smwpe
have the builder provide another lot and move the house.
or, he can build another.
has anyone out there had experience with saber, a contractor who repairs failed foundations?
or:  keystone foundations