I have purchased a new 10x12 Harbor Frieght greenhouse. I have watched many videos about basic structure repair to beef it up. I have figured out what I will do when spring comes. I am looking for any tips on the frame and base to make it secure. Any heating tips and etc. is appreciated.

Anna, I'm not sure what your intentions are for the "ground heat sink". In other words, I don't know whether you want it to keep the greenhouse from getting too hot in the summer or to keep the greenhouse from getting too cold in the winter. Normally a heat sink is used to keep something from getting too hot. For example, heat sinks are mounted on computer CPUs to keep them from getting too hot. They are intended to carry heat away as quickly as possible. Their analogy in an electrical circuit would be a ground wire, which "shorts" the circuit to the ground voltage through as little resistance as possible. I am in the process of excavating a foundation for a kit lean-to greenhouse that we ordered. Here in Maine the problem is to keep the greenhouse warm enough during the winter without spending a lot of money for fuel or electricity. During the summer we may not even use the greenhouse at all. So, during the winter I definitely don't want my heat to "sink" into the cold ground underneath the greenhouse. Instead of a heat sink, I am going to use a thermal mass of a rather limited amount of sand, gravel, and concrete pavers. That thermal mass will be insulated from the soil underneath by insulating foam, as much as I can afford. The thermal mass could be likened to an electrical capacitor, that stores current when the voltage is higher and releases current when the voltage starts to drop. That's what I want my thermal mass to do, namely warm up significantly during the day and release heat back into the greenhouse during the night as it cools off. Too much thermal mass won't warm up enough during the day. (A really large electrical capacitor can act rather like a short to ground.) Too little thermal mass will cool off too quickly during the night. There is a "happy medium" thermal mass that I am striving for. I intend to use enough insulation to prevent the floor from acting as a heat sink. I'm excavating deep enough to lay down several inches of insulation, and several inches of thermal mass over that. I certainly don't want to try to heat up the planet through the floor of our greenhouse. MM

zac- I've been quite satisfied with the oil-filled heater for my mild climate (Zone 8), and yours should be even better. It has two settings (750 W and 1500 W) and I have it on the 750 W setting with the thermostat at about 40F. Even though I've only got single pane glazing, the greenhouse is tight and the heater is able to maintain that temperature even on the low setting. As a safety precaution, I have a wireless thermometer that transmits to the house so I can check that the temperature is where I want it without having to go out with a flashlight at midnight! I also have an inexpensive, unvented, backup propane heater in case of an extended power outage (though I've never needed it). One other thought: a standard 15 amp circuit will trip at about 1800 W, so, if you run an electric heater at 1500 W and have other electrical stuff on that circuit, you could trip a breaker and lose power to the heater without possibly realizing it. seamommy- To lay my pavers, I actually excavated about 8" below finished floor height, then put in 4" of gravel and compacted it by hand, 2" of sand and compacted it by hand, and then laid in the 2" thick pavers and swept sand between the joints to lock them in. My perimeter foundation is about 2' deep (so that it's just below our frost line), and it's about a foot above grade. The advantage of a raised perimeter is that it effectively gives you more headroom. The process for doing the perimeter involved excavating down, and then putting in a 16" wide by 4" thick base (with a little rebar thrown in). Then I laid my courses of cinder block on top of the concrete base. When that was done, I dropped in some short pieces of rebar in the top holes and filled the voids with a soupy concrete mix to lock it all together. I then mortared on a decorative top course of colored concrete pavers and set my frame on that. The frame is set on caulking to keep out drafts, and is also bolted to the foundation. I also attached 1" thick styrofoam to the outside of the foundation to cut down on heat loss through the foundation. Here is what it looked like when I was almost done: I didn't put weed barrier in and haven't had any problems. Because I excavated for the perimeter foundation and excavated to prepare the floor, there wasn't any noticeable vegetation left under the footprint of the greenhouse, and nothing, including my blackberry vines, has returned in the 3 years I've had the greenhouse. The only slight problem I've had was last year when some ants started excavating sand out of the floor to make tunnels and I had to zap them with the little bait cans. If you are concerned about something growing back under a paver floor, barrier fabric would likely be a good insurance policy. If you went with an entirely poured perimeter foundation, that would work fine, too. I just didn't want to have to build forms and pay the minimum for the cement truck and pumper to come in. I managed fine with my little cement mixer for the concrete I did need and the mortar is easy to mix in a bucket. Good luck.

A greenhouse may be built upon a foundation of timbers, block, brick, or concrete. Elevating the foundation has the advantage of gaining height and headroom in some greenhouses. The greenhouse foundation should be stable, level, and square. A popular material for the floor is " crushed rock, but the floor may be concrete, dirt, mulch, brick, or tile. The installation of perforated drains beneath a porous layer of flooring helps to assure good drainage. When building a greenhouse, it is useful to insulate the foundation. This will prevent the loss of heat through the ground and permit the ground to act as a "heat sink." The installation typically consists of 1-2 inches of polyurethane or polystyrene insulation 1.5-2 feet deep around the foundation. Information provided by: Stressbaby