- Remove the existing sod and level the ground.
- If you have more than a few inches of fill, tamp down with a tamping device or a heavy lawn roller and wait a bit for the ground to settle.
- Spread the entire base area with 3-4 inches of 5/8 inch crushed clean gravel. Tamp this down to permit a firm well-drained surface for the greenhouse base and to help deter weeds or erosion inside the greenhouse. Optional: to prevent weeds entirely, before graveling, lay landscaping/weed cloth which has pre-drained holes in it, allowing water to drain through.
- Allow a small “tunnel” for electrical and/or plumbing lines, to be bronght in under the frame. You can use a 2” or 3” piece of plastic pipe (one under each side, or one front, and one back).
- Position the greenhouse perimeter base, anchoring it with ground anchors or other appropriate means.
- After the greenhouse walls and roof are on the perimetr base, install the interior flooring materials. See helpful hints below.
Pea gravel is not advisable under the wood (or other) bases, since it will never really pack down like crushed gravel will. It is only recommended for the interior floor if desired.
Brick flooring is a natural thermal mass, and is great for the heat collection on a winter day. After the daylight is gone the heat collected by the brick is released inside the greenhouse, slowing the cooling off process.
Weed cloth is great under the base gravel. It will allow water to drain through. Don’t use plastic that has no perforations. When you clean with a hose, or water a lot at one time, your excess water will have no place to go. You may create a too humid situation or be walking around in water that cannot readily drain away.
A concrete slab is not our favorite flooring. If you do use a slab, you will need to put in a sloped drain area. The perimeter, however, must be level. Without a drain in, you’ll have a puddle to stand in when you hose the inside.
Existing Concrete slab: If you are placing the greenhouse on an existing slab, it is probably slopped for natural drainage. If so you would then need to shim the greenhouse base, level it up, and then install drainage holes around the base so water can run out when you clean. If you install a drain, make it large enough, and put a screen over the opening to keep bark, small rocks, and dead leaves from clogging the drain.
On your deck. Decks often have spaces in between the boards. If so it is a good idea to install the greenhouse base, and bolt it down to the deck. An “L” bracket screwed to the deck and to the base is fine in 4 places around the base. Then get some 1 inch foam insulation pieces (used for insulation on roofs) and cover that with a marine plywood layer about 1/2 inch thick.
In this circumstance you will want to be cautious when mega watering, since a draining situation is more difficult to create. The insulation and plywood flooring helps to keep the greenhouse warmer in winter when cold winds blow up from underneath the deck.