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Home Maintenance And Repair - 01500312

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.

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.

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.

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.


This article was written by Anne Field, Extension Specialist, Emeritus, with reference from the USDA Disaster Handbook.

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MSU is an affirmative-action, equal-opportunity employer. Michigan State University Extension programs and materials are open to all without regard to race, color, national origin, gender, gender identity, religion, age, height, weight, disability, political beliefs, sexual orientation, marital status, family status or veteran status. Issued in furtherance of MSU Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Thomas G. Coon, Director, MSU Extension, East Lansing,MI 48824. This information is for educational purposes only. Reference to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned.

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