If you can, you would be better off digging into the hill for the base. Soil provides a good stable temperature source/sink.

I'd think twice about excavating into the hillside. With the slope you are reporting you'd have a 3-4' retaining wall on the up hill side in a GH with a 10-12 legth/with. I live up in Sonoma Co. and (if it were me) I'd sink concrete pilings into the exist slope and frame out level from there. You have to deal with steps or a ramp or somehting but it saves the cost and risk of the retaining wall.

Seems to me some solid sheet insulation beneath the floor would do what you need re: insulation were we live. 'Course the floor would have to be something solid.

your mileage will vary

Steve

I built mine on a very slight slope. We cleared the area out then leveled it going beyond the footprint of the greenhouse. We used concrete blocks for the floor and all along the outside to mainly keep critters out but also to keep it level and prevent erosion.
I live in the Santa Cruz area and the only problems I have had since we put it up early December is all the rain we had lately and the wind gusts in the storms. It didn't wash away even after having 17 inches of rain in a little over 2 weeks. And because of the blocks all around it and the fact we leveled the area around it we had no erosion.
Hope that helps you decide what to do.

Thanks everyone! Now I need to find the money! I've been wrestling with the buying decision for a year.
Jim

At the risk of posting this picture too much, here is my Harbor Freight greenhouse. I know lots of people put them down, but for $299 sale price you can't beat it. And we don't need a heavy duty one out here in CA. This one works just fine. I just got it for mainly growing veggies and flowers from seed to put out later. And for propagation of brugsmansias, roses and some other plants.

{{gwi:310876}}

wow that is a great deal...is that the 8x6 model that oyu have posted in your picture? how do you like it? as far as sturdy ness of structure and the panels..are they are a single pane correct?

That is the 8x6 model; the panels are 4mm twinwall polycarbonate. I have had one since September and am thrilled with it, as are many other HFGH owners in the forum. If you are interested, just browse the threads in this forum and you'll read and see how different folks have finished theirs off and how they're using them. Lots of pictures posted ... and help with the construction (because the instructions are really awful).

Here along the NJ shore, our average winter lows are in the low 20's. I've done some insulating, added a solar pool cover, and a fair amount of thermal mass and, so far, keeping it at or above 50 degrees when the sun isn't shining hasn't been awful. It's withstood a few windstorms without a problem and our only snowfall so far: 6" - not a lot, but it all came down in one night. Though, in Zone 9, you'll probably be more concerned with keeping it cool.

I wouldn't be without it ... unless it were replaced with a bigger one :-)

Diane

Add my name to the 'thrilled' column.

Dave
Milwaukee

Here is a link that might be useful: my HFGH