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FOUNDATION-SLAB SEPARATION NOTED
FOUNDATION-SLAB SEPARATION
NOTED
There are many methods of pouring slabs and
footings. Most are monolithic pours, or
"one piece" pours. Monolithic pours
are somewhat stronger than pours that have
"cold joints" in that the adhesive
strength of the cement and aggregate mixture at
the juncture of the slab and footing is
maintained. A common method of pouring footings
and slabs is to pour the footing (leaving 3 to 4
inches off the top to allow for the slab) then
the next day or so, pour the slab. This causes a
cold joint between the footing and the slab
which appears as a horizontal line around the
building's foundation. If the soil below the
slab is expansive and moisture enters the area
below the slab, or if the earth around the
perimeter of the foundation is allowed to dry
excessively, it is possible for the slab to lift
slightly off the footing. Ordinarily reinforcing
bars are installed and the lift is minimal.
However, in some older buildings
"rebar" was not required or installed
(or not installed properly) and lift of the slab
may be magnified. Another method of installing
slabs is to pour the footing to full height and
in a day or so, pour the slab within the
footing, using the footing as a
"form." Many garage slabs are poured
this way. If lift occurs with this slab system
you may never notice it because the crack is
usually under the frame or flooring and not
visible. One minor problem with this type pour
is that the crack can allow insects to enter the
building under the flooring. Nothing can be done
about this problem other than cosmetic cover-up
and actions to help prevent further lift. It is
recommended that you seal the crack with plaster
patch, stucco color coat, silicone caulk, or
similar products, to prevent water entering the
crack and/or insects from entering and causing
further lift or other discomforts. If you need
further assistance you should contact a Concrete
Contractor.
The above information was provided by TWI Systems Copyright 1995-2005 1-800-553-5660 |
