A garden bed that is elevated above the surrounding soil gets better drainage and allows for easier soil management. Depending on the garden bed height and the gardener's requirements, a tall garden bed can also make gardening possible for those who might not reach a ground-level garden easily. Elevating your garden bed also can allow gardening in challenging environments, such as on concrete in an urban landscape. Brick makes an inexpensive, environmentally sound choice for raised garden bed construction.
Determine the location of your brick elevated garden bed. Asses the height and permanency requirements for the bed edging to determine whether loose-stacking or concrete-and-mortar construction are most appropriate.
Prepare the elevated garden bed location. Remove turf and loosen the soil with a shovel to a depth of 12 inches or more in a garden soil location, then use a metal rake and level to ensure a flat construction surface. In an urban concrete or asphalt garden location, lay bricks loosely in a single layer to the interior dimensions of the desired garden bed.
Pour a concrete footer for a permanent brick elevated garden bed. Check the level of the ground or asphalt when permanent construction is not desired. Lay the first course of bricks on the concrete footer, leveled ground, or asphalt, using a header bond--placing the bricks perpendicular to the edge of the garden bed, so that the wall is the thickness of the brick's long edge--for greater stability. Secure the bricks with mortar as you work for permanent construction, or tightly stack the bricks, tamping them into place with a piece of 2 by 4 without mortar for non-permanent construction. Use the non-permanent method for construction on asphalt.
Stack courses of bricks, checking the level after each course, until you reach the desired height. For free-standing container beds on asphalt, make sure the walls are at least 12 to 18 inches high. Set a second round of bricks to double the thickness of the wall on tall installations. Allow the mortar to cure if used, and top it with coping or a painted board to keep water out and allow a comfortable sitting surface.
Line beds constructed on asphalt with weed cloth, which will keep topsoil in but allow water to drain. Mix good-quality topsoil with well-aged compost in roughly equal proportions. Fill your elevated brick garden bed with the soil mixture, water lightly, and allow the soil to settle. Top the soil level off and water again before planting.