Michigan
State University Extension
Home Maintenance And Repair - 01500312
06/24/03
Cleaning and Repairing Flooded Basements Entering
Before you enter a flooded basement:
1. Turn off the electricity, preferably at the meter.
2. Check outside cellar walls for possible cave-ins, evidence of
structural damage or other hazards.
3. Turn off gas or fuel service valves.
4. Open doors and windows, or use blowers to force fresh air into the
basement.
Pumping
Do not use an electric pump powered by your own electrical system. Use
a gas-powered pump, or one connected to an outside line. Fire
departments in some communities may help with such services. More
damage may be done by pumping water from the basement too soon or too
quickly, than from letting the floodwater remain. Water in the basement
helps brace the walls against the extra pressure of water-logged soil
outside. If water is pumped out too soon, walls may be pushed up.
To help prevent such structural damage, pump the water from the
basement in stages. Remove about a third of the water each day. Watch
walls for signs of failing. If the outside water level rises again
after the day's pumping, start with a new water line. The soil may be
very slow to drain, but do not hurry the pumping. Whatever is submerged
in the flooded basement will not be damaged further by delaying the
pumping; serious structural damage may be prevented.
Cleaning
After water has been pumped from the basement, shovel out the mud and
debris while it is still moist. Hose down walls to remove as much silt
as possible before it dries. Floors and walls may need sanitizing,
particularly if sewage has entered the basement. Scrub walls and floors
with one of these sanitizing solutions;
1. Chloride of lime (25% available chlorine). Dissolve a 12-ounce can
in 2 gallons of water.
2. High test hypochlorite (65% available chlorine). Stir 5 ounces into
2 gallons of water.
Oil stains in basements caused by overturned or damaged oil tanks may
also be a problem following flooding. Commercial products (such as
Neutroda) will help neutralize fuel oil spray for hard to reach places.
To remove oil stains and destroy odor, wipe up excess oil, shake or
spray product on the spot according to manufacturer's directions, and
let it set.
Repairing
Check supporting columns, beams, walls, and floors. Structural damage
to flooded basements usually includes buckled walls, settled walls, or
heaved floors. Buckled walls are evidenced by horizontal cracking and
walls moving out of plumb. When this condition is minor, you need not
repair the wall immediately. However, any noticeably buckled wall will
eventually collapse from normal ground pressures and season temperature
changes. When buckling has seriously weakened the wall, rebuild the
damaged parts immediately. Build pilasters into walls over 15 feet long
for reinforcement. Pilaster spacing should be 12 to 15 feet.
Settled walls and footing are indicated by vertical cracks either in
small areas or throughout the structure. Repairs are difficult without
special equipment. Contact a reliable contractor for this work.
Heaved floors are those that have not returned to their original level,
or have cracked badly. You may need to construct a new floor.
1. Remove old, broken concrete.
2. Place 6 inches of gravel fill on the basement floor surface.
3. Cover area with a polyethylene vapor barrier.
4. Lay a 4 inch concrete floor with mastic joints between the floor and
walls. The floor should be reinforced with steel. Welded wire
reinforcement placed at mid-height in the slab is a minimum
reinforcement.
If a floor is badly cracked, but has returned to its original level,
and if there is sufficient headroom, place a new floor over the old
one. Add a vapor barrier between the two floors. The new floor should
be at least 2 inches thick.
In houses without basements the area below the floor may be completely
filled with mud. Remove the mud as soon as possible to avoid rotting
joists or foundation wood.
References
This article was written by Anne Field, Extension Specialist, Emeritus,
with reference from the USDA Disaster Handbook.
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