16, 2003 - FPA
Committee Paper FPA-RC-01, "Post Foundation Repair Performance. A
Study of Foundation Repair Failure"
Speaker: Ann Nelson (tel.
713-473-2382, 281-420-1739), Member, past president of the FRAT, a
founding member of FRAT and chair of the FPA's Repair
Owner/Operator/President of Nelson Construction and Foundation Repair
along with committee members Dan Jaggers of Olshan Foundations,
Kenny Dutton of Du-West Foundation Repair and Chris Cates, also
with Du-West presented their Repair Committee's paper entitled,
"Post Foundation Repair Performance - A Study of Foundation
Repair Failure". Revision C, which had been successfully peer-reviewed
by the FPA was presented and handed out to the audience. Some changes
will be incorporated based on the audience's comments and questions.
The final revision will be published at: http://www.foundationperformance.org/committee_papers.cfm by August 1, 2003.
presentations to a room of about 50 addressed the various types
of foundation repairs available such as mud jacking or helical piers
along with maintenance systems such as root and moisture barriers,
giving common reasons why they do not always perform as intended.
made by the speakers:
- Mud jacking,
mud pumping and foam injection to lift foundations remains a risky
operation due to the possibility of over-pressuring and clogging
leaking sewer lines.
- Piling systems
such as Ram Jacking or Pressed Piling need to be driven to refusal,
i.e., to the point of lifting the foundation rather than just
a certain pressure reading and refusal should not be checked after
setup occurs (in clay). Doing so can give about a 4:1 safety factor
on the piles.
for helical piles and ram jack piles need to be hot-dipped galvanized
or epoxy-coated or they will not last in this area due to corrosion.
- Often the
repairs fail because large trees were removed, trees which were
there decades before the foundation or the foundation addition
(being repaired) was constructed. In these cases, the removal
of the trees allowed rehydration of the clays which heaved the
foundation off the repair piles or piers.
- French drains
and sprinkler systems if used should be at least several feet
from the foundation. Downspouts should not be tied into French
drains. They should go into a closed system.
- Root barriers
are helpful in controlling subsidence from nearby trees but roots
tend to grow over and under them. The owner needs to maintain
the roots growing over. Maintenance is not feasible for the roots
growing below. Root barriers can cause heave due to rehydration
as a result of cutting the roots.
pier caps of drilled and cast-in-place concrete bell-bottomed
piers are too thin and break off when the jack is removed from
the center and load is transferred to the thinner edges.
piers tend to lay over if not accurately installed at the correct
angle of about three (3) degrees.