Once your greenhouse is constructed, you'll need some benches to hold potted plants, trays, tools and supplies. Placing potted plants on benches in the greenhouse raises plants above ground level for optimal air circulation and accessibility for watering and maintenance. Benches must be strong enough to hold the weight of potted plants, and made from materials that will perform well in a greenhouse environment. They can be simple wooden slats on concrete blocks or complex raised hydroponic grow beds. Useful wooden benches are well within the average do-it-yourself skills and abilities.
Place four of the cement blocks in a 3-foot by 6-foot rectangular form, one in each corner, to begin the foundation for the bench. Check to see if the blocks are on flat, level ground with the level tool.
Stack the remaining eight blocks on the corner blocks, three high, to create the legs of the bench. Use the level to check that the blocks are all the same height and on a level surface.
Sand all the wood pieces to remove rough edges and splinters.
Place the 6-foot pieces of lumber on the ground or on a large work surface. Position them 3 feet apart, parallel to each other.
Place the 3-foot pieces of lumber vertically across the longer pieces, every 6 inches, starting at one side of the longer wooden pieces.
Nail or screw the shorter pieces of lumber securely into the 6-foot pieces to construct the bench top.
Brush the waterproofing sealant onto the wood and let it dry.
Place the completed wooden slat bench top onto the cement block legs to complete the greenhouse bench.
If you're using hollow cement blocks, metal pipe or rods sunk into the ground in the middle of the cement blocks will add stability. Adjust the bench height by adding extra cement blocks.