Sandbags are typically used to create a simple flood barrier in emergencies or times of distress when there is not enough time to build something more effective. Stacking sandbags correctly ensures that they will function effectively. Stacking sandbags in the correct fashion decreases the chances of failure and increases the overall effectiveness of the sandbags.
Dig a ditch below ground level between the area being protected and the expected flood water. This isn't necessary if the sandbags will be laid on a concrete surface.
Line the ditch with a sheet of polyethylene. If concrete is being used as the bottom surface simply lay a sheet of polyethylene onto the concrete
Fill the sandbags with sand using a shovel. This is best accomplished by having one person hold the sandbag while another person shovels the sand. The bags should be half to two thirds full. The bag, when filled, should lie flat, according to Louisiana Floods. Seal the sandbags using rope or by folding the opening over the top of the sandbag, sealing it due to the weight of the sandbag on top of it.
Place the first layer of sandbags on top of the polyethylene sheet and then fold the sheet over the sand bags to create a water proof barrier. Walk on top of each sand bag to compact it into place.
Stack as many layers of sandbags as necessary -- up to five sandbags high. Three high is typically recommended, so adjust the height depending on the severity of the flood. Fold the plastic sheeting through the sandbag formation while stacking the sandbags. It should form an S shape when folded throughout the sandbags.
Insert cotton caulking into any leaks that appear in the sandbag wall during the flood. If a leak isn't addressed immediately it could lead to the eventual failure of the sandbag wall.