Sandbagging & Flood Barriers

When a flood is coming, sandbags can help divert shallow water around a building or protect a doorway. But they’re heavy, slow to build, and not a seal against rising water. Doing it right means starting early, building properly, working safely and knowing when to leave. Your life is worth more than your house.

• Homeowners
• Families
• Flood Preparedness

What sandbags can and can’t do

• They can divert or slow shallow flowing water, protect low openings such as doors and garage entrances from small flooding, and help hold back water from a few inches up to about two feet.
• They can’t stop deep or fast water, or hold back water for long. Sandbag walls leak, seep and can fail, especially when poorly built. Water also seeps up through the floor and walls from groundwater.
• Walls higher than about 2 to 3 feet need an engineered design, and the base gets very wide, so most home walls should stay below this. For deeper threats, rely on evacuation and permanent flood protection.
• Sandbags are not a reason to stay in an area under an evacuation order. See Hurricanes & Floods and Family Emergency Plan.
• Check with your local emergency management office, public works department or fire department for sandbag locations, rules and flood risk.

Planning ahead

• Know your flood risk and where water usually comes from. Check flood maps and local alerts.
• Get supplies early: empty bags (burlap or polypropylene), sand (or soil, if sand isn’t available), shovels, plastic sheeting, rope or ties, gloves, a dust mask and boots. Local governments often offer free sand and bags, and some provide pre-filled bags.
• Make a plan for where the barrier goes, how many bags you need, and who will help. A rough guide: about 40 bags makes a wall about 1 foot high and 20 feet long, but it varies, so ask your local officials.
• Shut off utilities and move valuables before the water arrives. See Shutting Off Utilities.
• Buy or consider flood insurance, since homeowners policies generally don’t cover flooding. There is usually a waiting period before it takes effect.

Filling and tying bags

1. Fill each bag about half to two thirds full, to about 12 to 15 pounds. Overfilled bags are too heavy and don’t stack tightly. A half-filled bag lies flat and molds to its neighbors.
2. Use sand if you can. Sand drains and shapes better than clay or dirt. Use whatever local officials supply. Use a funnel or have one person hold the bag open and another shovel.
3. Fold the top of the bag over (or tie it, if you want a tied bag for a barrier) and set the bag on the ground. Many walls use untied bags folded under so that the open end is hidden, and the bags interlock better.
4. Work in teams. Fill bags in a shady, safe spot, then move them to the wall. Don’t fill bags in the water.
5. Wear gloves and a dust mask when shoveling dry sand, since sand dust can contain silica. See Silica.

Building a sandbag wall

• Choose the right spot: build as close as you can to the area you’re protecting, but a few feet away from the building, on a flat, firm surface. Clear debris and level the ground. Water flows around walls built across a slope, so the barrier should run so as to turn the water away.
• Lay plastic sheeting (heavy plastic) on the flood side of the wall, with the bottom edge under the bags and the top folded over, to cut seepage. Don’t put sheeting between bags in a way that makes them slide.
• Stack like bricks: lay the first layer lengthwise with the folded ends toward the water, then place the next layer so the seams are staggered, and pack each bag tight against the next, stomping or tamping it into place. Use a pyramid shape that is about three times as wide at the base as it is tall, for stability.
• Keep walls low (under 2 to 3 feet), unless designed by an engineer. Extend the wall past the threatened door or opening on both sides.
• Protect doorways and openings with bags placed against the door and plastic over the lower part, but keep an exit route you can use.
• Don’t block drains or direct water onto a neighbor’s property, and don’t put bags on drain covers unless officials say so.
• For small seeps, extra bags or sealant may help. Water will get through, so keep a sump pump and a backup. See Sump Pumps & Basement Flooding.

Working safely

• Lift properly: bend your knees, keep your back straight and hold bags close to your body. Don’t twist. Use a bucket brigade or a cart. See Lifting & Ergonomics.
• Pace yourself and work in teams to avoid exhaustion and heat illness. Drink water and take breaks. See Extreme Heat and Home First Aid.
• Watch the weather and the water. Don’t work during lightning, strong winds or rapidly rising water. See Thunderstorms, Lightning & Hail.
• Keep children and pets away from the work and the water.
• Wear boots, gloves and a reflective vest if working near roads, and watch for traffic.
• Stay out of floodwater. It hides holes, debris and sharp objects, carries sewage and chemicals, can be electrified and moves faster than it looks. Six inches of moving water can knock you down. See Flooded Roads and Downed Power Lines.
• Leave when told to. Never stay to defend property after an evacuation order.

Alternatives to sandbags

• Water-filled barriers and tubes that fill with water when placed, and are light to move.
• Expandable or gel flood bags that absorb water and swell, and are lighter than sand.
• Flood gates and door shields, and aluminum or plastic barriers that are installed at doors and garages.
• Permanent measures: raising utilities and appliances, flood vents, backflow valves, grading and drainage. See Disaster Cleanup.
• Compare cost, speed and reliability. Some products are tested for flood protection, so check for certification and the maker’s instructions.

After the flood: used sandbags

• Treat used sandbags as contaminated. Floodwater often carries sewage, chemicals, oil and bacteria, which soak into the sand and bags. Wear gloves and wash your hands after handling them.
• Don’t reuse bags that touched floodwater for gardening, children’s play areas or other things where people touch sand, or put them near food or drinking water.
• Dispose of them as local officials direct. Many communities collect used sandbags, or tell residents how to empty them in a safe place, and what to do with the bags.
• Clean up and dry out quickly to limit mold. See Home Mold.
• Unused, clean sand and bags can be stored dry for next time, if bags are in good shape.

Sandbag checklist

• I know my flood risk and local sandbag rules; I started early
• Bags are half to two-thirds full, and stacked like bricks in a pyramid with plastic on the flood side
• My wall is under about 2 to 3 feet, and I know it won’t stop deep or fast water
• I lift with my legs, work in a team and stay out of floodwater
• I will evacuate immediately when told to
• I treat used sandbags as contaminated and dispose of them as directed

Last updated: October 4, 2026