How to use sandbags for flooding: filling, stacking, and what they can't do

What sandbags can and can't do

The US Army Corps of Engineers' Jacksonville District puts it plainly: "Although sandbags do not guarantee a watertight seal, they are a proven deterrent to costly water damage." They are a way to slow water at a low opening, not to stop a flood.

The Corps' Rock Island District says a 3-foot-tall barrier is the highest recommended sandbag barrier, and that "for each foot high, the barrier needs to be 3 foot wide." The Jacksonville District calls five feet "the practical limit of a sandbag levee" and prefers 3 feet. The Jacksonville District adds: "If a higher levee is needed, alternate means of construction should be considered." Talk to your local emergency management office.

Two more cautions from the Rock Island District: "Don't assume a building wall is rated to hold flood waters," and "Always assume a pump will be needed." It also says any underground pipes or conduits will need to be plugged or closed.

Where to get sandbags

The Jacksonville District advises private individuals to "go to your local authorities (i.e. levee district commissioners, city, count[y], etc.) for information," and notes there are several commercial suppliers across the US. Search your city or county's emergency management page, or call its non-emergency line, before you spend money.

How to fill sandbags

The Jacksonville District says to fill bags one half to two thirds full and tie them so the bag lies flat; a properly filled bag weighs between 35 and 40 pounds. The Rock Island District, which gives a weight of about 50 pounds for a bag filled this way, says to fill each bag about half to slightly more than half full, and offers a test: "Tuck opening underneath, facing upstream. If you can't tuck, it's filled too full."

Overfilling matters. The Jacksonville District says: "Overfilled bags and bags tied too low leave gaps in sandbag levee allowing water to seep through." The Rock Island District adds that filling stations should be outside the area you are protecting, especially when using volunteers.

How to stack them

Sandbags, the Jacksonville District says, "should be placed flat on ground, overlapped, tamped into place, and stair stepped." Offset each row by half a bag length so the joints do not line up, and compact each bag by walking on it as you build.

For extra protection, both districts describe plastic sheeting over the barrier. The Rock Island District says to use sheeting at least 4 mil thick (6 mil preferred) on the water side up to the top of the barrier, with sandbags on top so currents or wind do not move it. The Jacksonville District says to lay plastic on the downstream portion of the levee first, then work upstream with a two to three foot overlap.

Lifting, handling and staying safe

OSHA says "manually filling, moving and placing sandbags is physically demanding work." Its advice includes: "Lift with your legs, not your back," use equipment to fill and move bags where you can, and use gloves. The Corps adds to wear gloves while filling and, after handling treated bags, avoid contact with your eyes and mouth.

National Weather Service: "A mere 6 inches of fast-moving flood water can knock over an adult. It takes just 12 inches of rushing water to carry away most cars and just 2 feet of rushing water can carry away SUVs and trucks. It is NEVER safe to drive or walk into flood waters."

Ready.gov: "Do not touch electrical equipment if it is wet or if you are standing in water. Turn off the electricity to prevent electric shock if it is safe to do so." It also says: "Use a generator or other gasoline-powered machinery ONLY outdoors and away from windows." See flood preparedness for the full list.

After the water: used sandbags and flood insurance

The Rock Island District says sandbags that have contacted or been loaded with flood water "must be disposed of at an appropriate landfill or the local ordinance," and that "sand that flood waters have contacted is NOT appropriate for sandboxes." Your city or county can tell you where to take them.

Sandbags do nothing for the cost of a flooded home. Ready.gov: "Homeowner's insurance policies do not cover flooding. It typically takes up to 30 days for a policy to go into effect, so the time to buy is well before a disaster." FEMA's National Flood Insurance Program says there is typically a 30-day waiting period between purchase and the effective date, with exceptions such as insurance bought in connection with a mortgage loan.