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Mudjacking – Raise Those Settled Slabs
by Martin Newmark
Copyright 12/2006
Mudjacking
is a process by which concrete slabs or “flatwork” (driveways,
sidewalks, basement floors) are raised after settling.
Settling
flatwork is extremely common throughout the front range. A safety
concern with settled flatwork is tripping hazards. This occurs when
adjacent slabs settle at different rates resulting in one slab being
higher than the other. In the dark or in the middle of the day it’s
possible to kick this small deviation in the surface and stub a toe or
trip and fall.
Other
problems arise if the flatwork is sloping toward the building. In this
case water runs toward the home instead of away from it. This can be
problematic because water next to a foundation can eventually seep into
the home or cause the foundation to settle and possibly become
structurally unsound.
One
solution to settled flatwork is to remove the existing surface and
replace it. This can be a costly endeavor. First the old slab needs to
be removed – broken up, loaded up, hauled away, and then dumped. Next
the surface would need to be prepared for a new slab. Finally the new
slab needs to be poured. The cost of this solution, for a two-car wide
driveway, can run around $2600-$3400.
Mudjacking
may be a more affordable alternative solution. Small holes are drilled
in the existing slab and a mud slurry is pumped into the holes and under
the existing slab. This fills any voids under the slab and eventually
raises the slab so that it’s even with adjacent surfaces or provides a
positive slope away from the structure. A typical minimum cost for this
service is around $300 with the average mudjacking job costing around
$600, a much more cost effective solution than replacement.
While
mudjacking can solve settling problems it should not be used as a
solution for raised flatwork. Raised flatwork occurs when there is
expansive soil under the concrete slab. When water seeps under the slab
the soil expands and raises the slab above it. The only solution to
raised flatwork is replacement. Determining the difference between
raised and settled flatwork can be
tricky. Don’t try to do it
yourself. Rely on the expertise of your home inspector or concrete
specialist for this analysis.
Another
problem that mudjacking won’t solve is a slab with many cracks in it.
Trying to fix a slab with lots of cracks is like trying to walk on
boards that are floating on water. Good luck!
Finally
you might wonder if mudjacking is a permanent solution. The answer is:
many times yes, and sometimes no. Sometimes the slab will continue to
settle and additional mudjacking will be necessary at a later date. The
best thing you can do to make mudjacking a permanent solution is to make
sure the cause of the settling is addressed. Causes like a gutter
downspout spilling water at the edge of the concrete slab should be
corrected. If you don’t re-route the downspout to direct the water
away from the slab your problem will come back, guaranteed. If the cause
is due to backfill from the construction process continuing to settle,
you may just have to re-mudjack it. Still it’s less expensive than
replacement.
© 2006 - Abacus Inspection Service
303-554-5840
Serving Colorado's Front Range