How do I Build a Base for an 8X6 Greenhouse?

Select 4-by-6 wood timbers that are naturally resistant to decay such as cedar, redwood or cypress. If you use a frame for the greenhouse made of aluminum, you can only use pressure-treated lumber with a barrier. Pressure-treated lumber has chemicals that will damage aluminum framing, and you must install a polyethylene or vinyl barrier at least 10 mil thick between the wood and frame.

Choose a suitable location that is level, free from debris and has adequate solar exposure.

Cut the timbers to appropriate lengths as instructed by your greenhouse owner's manual. Lay the timbers in place and remove any large dirt clods and twigs that may be in the way. Set the level on top of the timbers and make any adjustments under the timbers to make sure the entire base is level.

Attach the timbers together using lag screws. Pre-drill the holes through the timbers using a drill bit that is slightly smaller in diameter than the lag screws. The lag screws should be three or more inches longer than the first board you screw them through to attach them securely.

Lay the landscaping fabric under frame. Installing the landscape fabric under the base allows for good drainage and keeps any weeds to a minimum inside the greenhouse. Pick up each corner of the frame and carefully slide the fabric under. Ensure that the fabric protrudes under each timber. Trim excess fabric even with the outside of the timber.

Square the base by measuring diagonally from the opposite corners. Adjust the base until the two measurements are the same.

Anchor the base to the ground using an earth anchoring system. Carefully installing the earth anchors according to the manufacturer's instructions will create a securely anchored base for the greenhouse.

Complete the base by filling it with at least three inches of sand or pea-sized gravel. Pea gravel works well and allows water to drain through the base quickly. The base is now complete.