Do sandbags really stop flooding? How to use them the right way

Sandbags can help protect a home from shallow flooding during a hurricane or tropical storm, but only when they are filled, stacked and placed correctly.

Used improperly, sandbags may leak, collapse or redirect water into another part of a home. They are also not designed to stop storm surge, deep flooding or fast-moving water.

Emergency management and flood-control experts say sandbags work best as a temporary tool to divert minor floodwater away from vulnerable areas such as doorways, garages, vents and low windows.

Read on for your guide on how best to use sandbags, what to avoid and how to dispose of them after the storm.

What sandbags can (and cannot) do for your property

Sandbags can help redirect shallow, slow-moving water, reduce water entering through doors or garage openings, protect low vents and ground-level windows, and guide runoff toward a safer drainage area.

Residents should never rely on a sandbag wall as a reason to ignore an evacuation order. Storm surge and rapidly rising floodwater can overwhelm temporary barriers with little warning.

How to fill sandbags correctly

PINELLAS PARK, FLORIDA - AUGUST 29: Edgar Rocha (L) and Paul Xy fill sandbags at the Helen S. Howarth Community Park ahead of the possible arrival of Hurricane Idalia on August 29, 2023 in Pinellas Park, Florida. Hurricane Idalia is forecast to make landfall on the Gulf Coast of Florida on Wednesday morning. (Photo by Joe Raedle/Getty Images)

One of the most common mistakes is overfilling the bags.

The U.S. Army Corps of Engineers recommends filling each bag only about one-third to one-half full. Partially filled bags are easier to carry, flatten more effectively and fit tightly against neighboring bags.

A filled sandbag can weigh 30 to 50 pounds, so gloves, closed-toe shoes and eye protection are recommended.

Do not tie the bags too tightly if they will be stacked. Leaving enough room for the sand to shift allows each bag to mold into the gaps around it.

How to stack sandbags

John Milt places sandbags in preparation for flooding near the banks of the Cumberland River in Clarksville Tenn., Friday, April 4, 2025. (AP Photo/George Walker IV)

Before placing sandbags, remove sticks, rocks and other debris from the ground.

Lay the bags flat and lengthwise, parallel to the expected direction of the water. Fold or tuck the open end underneath the filled portion of the bag.

Each new bag should overlap the previous one by about half its length. Press down firmly to flatten the bag and remove gaps.

For multiple layers, stagger the seams as if building a brick wall. Avoid stacking bags directly on top of one another with all the seams aligned because this can create channels for water.

Sandbag walls taller than a few layers need a broad base. A narrow, vertical stack is more likely to tip or fail under pressure.

Use plastic sheeting for better flood protection

Sandbags alone are not waterproof.

For doors, garages and low windows, emergency officials often recommend placing heavy plastic sheeting or waterproof material against the opening, then using sandbags to hold it securely in place.

The plastic acts as the water-resistant layer, while the sandbags provide weight and help close gaps along the ground.

The sheeting should extend beyond both sides of the opening and lie flat beneath the first row of bags.

Where to place sandbags around a home

Homeowners should focus on the lowest and most vulnerable entry points, including exterior doors, sliding doors, garage doors, basement windows, low vents and utility openings.

Avoid building a complete ring of sandbags around a home unless flood professionals recommend it. A barrier that blocks the natural drainage path can trap rainwater against the building or redirect water toward a neighboring property.

Residents should also make sure sandbags do not block storm drains, roadside drainage channels or emergency access routes.

What can be used instead of sandbags?

Traditional sandbags are inexpensive but require significant time, labor and storage space. Several alternatives may work for shallow flooding, but no temporary barrier should be considered dependable protection from storm surge or severe flooding.

Some facilities have invested in flood protection, including Tampa General Hospital in Florida, which has successfully used the AquaFence barrier, designed to withstand floodwaters up to 15 feet.

However, most renters, homeowners and business owners can use alternative, lower-budget options.

Water-filled flood barriers are large tubes or modular systems that can be filled with water and placed across driveways, doors and other openings. They can be quicker to deploy than hundreds of sandbags, but they must be rated for the anticipated water depth and installed on a suitable surface.

Reusable doorway flood barriers or removable panels may create a tighter seal than loose sandbags. Some are designed specifically for garage doors, exterior doors and commercial buildings. Installation instructions must be followed carefully because water can enter around the sides or beneath the barrier if the surface is uneven.

Absorbent flood bags expand when they come into contact with water. These products may help control minor leaks or nuisance flooding, but homeowners should not treat them as protection from storm surge, fast-moving water or major flooding.

Heavy plastic sheeting can also help reduce water intrusion when it is tightly secured and supported by a weighted barrier. Plastic should not be used by itself in strong winds or moving water.

File image: In this Dec. 8, 2012 photo, the Richard P. Kane Wetland Mitigation Bank, a long barrier wall made of large baskets filled with sand and dirt, runs through the Meadowlands in Moonachie, N.J.(AP Photo/Mel Evans)

Straw or hay bales can sometimes be used to slow or redirect shallow surface runoff, particularly on rural properties, slopes and areas where erosion is a concern. However, loose bales should not be treated as a direct substitute for a properly constructed sandbag barrier.

The U.S. Army Corps of Engineers lists straw bales as a possible economical flood-fighting material when they are incorporated into a larger, reinforced barrier. The bales must be firmly secured with long stakes or reinforcing bars and weighted with filled sandbags. As straw becomes wet, it swells and becomes heavier, which may help close some gaps in the barrier.

Can sandbags be reused after a storm?

Sandbags that were exposed only to rainwater may be dried and stored for future use.

They should be kept in a dry location away from direct sunlight and moisture. Wet bags can develop mold, weaken or break down over time.

Residents should check local regulations before emptying or disposing of the bags. Some communities establish sandbag drop-off locations after hurricanes, while others require disposal at a landfill.

How to dispose of sandbags after flooding

Sandbags that came into contact with floodwater should be treated as potentially contaminated.

Floodwater can contain sewage, fuel, pesticides, bacteria, animal waste and other hazardous substances.

Wear gloves, protective clothing and closed-toe shoes when handling used bags. Avoid touching your face and wash your hands thoroughly afterward.

Flood-exposed sand should not be reused in children's sandboxes, playgrounds, vegetable or herb gardens, or other areas where people and pets will have frequent contact with it.

Sandbags visibly contaminated by sewage, petroleum products or chemicals may require special disposal. Residents should contact local emergency management, public works or solid-waste officials for instructions.

Do not dump sand or bags into storm drains, canals, rivers, wetlands or along roadsides. Sand can clog drainage systems and create additional flooding problems.

Full sandbags may also be too heavy for normal curbside collection, so residents should confirm local pickup rules before placing them with household trash.