How to Build Concrete Block Wall for a Greenhouse

If you live in a cold climate and love to garden, you've probably dreamed of having your own greenhouse. Heating a greenhouse through a northern winter can be expensive, though. One solution is to build your greenhouse on top of a short concrete block wall. If you build your wall only three or four bricks high and set the greenhouse on top of it, you will reap several benefits. First, the concrete will cut down on drafts. Second, in order to get full sunlight, the plants need to be grown on shelves set above the level of the concrete block wall. This means that you can lower the temperature of the greenhouse because the cold air will collect in the area below the top of the wall and the plants will grow in the warmer air above it. Finally, you can store garden tools and supplies in the cooler area under the plants.

Things You'll Need

• Stakes and string Concrete blocks, including "half" blocks Mortar Trowel Greenhouse kit

Instructions

1. Install a concrete slab for the floor and base of your greenhouse. The dimensions of the concrete slab are part of the specs included with your greenhouse kit.

2. Put up a guideline. Put a stake at each corner of the concrete slab, and another every 2 to 3 feet along the perimeter. Run a string marker line around the perimeter of the concrete slab by attaching it to the stakes. Put one string a few inches above the ground and another a few inches higher. These will serve as your guides when laying the concrete blocks.

3. Prepare mortar. Mix mortar according to manufacturer's directions.

4. Lay concrete blocks. Begin at one corner. Throw mortar down and line up a concrete block with the marker line and the edge of concrete slab. Throw additional mortar onto one side of block and the concrete slab right next to first block. Set the second block, making sure the mortar "glues" the sides of the blocks together. Continue around perimeter of concrete slab.

5. Lay the next course of concrete blocks. Stagger the blocks so the joints of one course are directly under the center of the blocks of the course directly above it. Begin at a corner by laying one of the "half" blocks. Continue building wall until it is the desired height.

6. Build a small stair leading from the concrete slab to the top of the wall at the place where the door goes. Make the stairway out of concrete blocks with the same number of steps as you have courses of blocks in the wall. Build a matching stair on the outside of the concrete wall.

7. Allow the mortar to cure according to the manufacturer's instructions.

8. Build your greenhouse. Follow the manufacturer's instructions to build your greenhouse. Instead of attaching the foundation of the greenhouse to a concrete slab, attach it directly to the top of your concrete block wall.

Tips & Warnings

• This system also works with a concrete block wall that is only one course high. The point is to raise the level of the greenhouse glass walls above the ground. This gives the cold air a place to gather that is below the level at which the plants are growing.