Careful now! Are you sure your "2nd story deck" is structurally sound enough to support it? Do you need a building permit? Be aware that the high humidity inside will really deteriorate the attached building. Things rot faster, rust faster, etc. If everything checks out, a solarium type design should work well.

What kind of deck is it, and what sorts of changes to it were you planning on making? If air can circulate underneath your proposed gh, you will have problems keeping it warm in the winter.

-Bruce

The house was turned into an upstairs/downstairs duplex before we purchased it and the deck was the entrance for the upstairs tenants. It is build quite soundly and has been treated. We had planned on sealing it again before erecting the greenhouse.
I was interested in the 6X8 Rion, mostly for starting seeds and maybe some overwintering. One of my concerns is if I decided to "expand" my interest for winter use, is the heating issue you mentioned, Bruce.
I had thought about some sort of heavy duty plastic as a barrier used on the flooring during the worst of winter...but I'm not sure? I guess that is why I'm looking for advice, huh? :)
I have no other place for a greenhouse with the correct placement. I'm hoping to be able to make this area work for me both practically and efficiently, but it may just end up being a "dream" of mine. Thanks for your input!

I concur with the comment about losing heat, but then- 6 X 8 ft. isn't a large area and constructing a raised, very well insulated base to set the GH on, wouldn't be that much of a project.

The base and insulation however, would be the easy part.

All you would need are some treated 1 X 8's or for really thick insulation; 1 X 10's, and sheets of Type 250 rigid foam insulating, set down in layers to fill in the space. That material is so dense, it's used under concrete in heated garages.

The trick then, would be drainage and for that, you would need to lay the foam on just enough of a slope to allow water to run to one end, to a channel drain, connected to an outlet line going straight down, and for that, you would also need to cut a hole in the deck.

But you could then lay cement board over the foam and top it with whatever type of flooring you want. I finished mine in glazed quarry tile, but vinyl would have worked too. In fact, with such a small area, glueless, seamless vinyl would be a fairly innexpensive finish. Just run a bead of acrylic sealer around the edges to prevent water from creeping under it and perhaps, top that with some vinyl shoe around the outside edges as well, to make sure the edges stay tightly down, and sealed. You would have a bright, easy to clean floor, with the added insulating bouns of the foam backing on it.

But that drain line, exposed to the air from the point where it leaves the GH and gets down to ground level would have to empty to where it couldn't freeze. So unless you have access to an existing frost proof drain line close by, such as a clean-out trap in the yard, and could trench below frost line to connect to it....

Your other option is a drywell set below your frost line directly under the outlet from the GH. Presuming you would only be discharging runoff, you could water plants in winter and not have the drain fill and freeze.

You would have to test it, to learn how quickly the drywell emptied, but just to handle runoff from such a small GH even a small one, say about 20 - 30 gal. should do, and you can buy them ready made for not much money. The only heavy labor would be in digging the deep pit to hold it.

As long as the drain isn't filled and freezes, thick walled PVC won't burst, just because it's lined with ice.

Or, forget the drywell and only use the GH in warm weather, but you would still need drainage or indeed; the deck will rot out from under it- PDQ.

BTW: Yes, you could install an insulated, double walled drain line and that would help, but would still need a place to discharge what goes through it in freezing weather.

I'm not trying to discourage you; just offering a possible means of your being able to mount a GH atop a second story wood deck, regardless if you plan to use it all year with heat, or only in the warm months.

Also, setting a GH in full sun in a south facing position will result in a far greater challenge than keeping it warm in winter.

Use some imagination, grunt work and engage the latest in building materials and keeping any GH warm in winter is easy compared to preventing it from becoming a blistering oven in summer.

I had a Sundog (HFGH type) on an elevated, treated deck for a year, and replaced it with a Rion 8x12 last fall. No problems with either - yet. I floored both with water-permeable boat carpeting for a wind barrier, which seems to work. No problems heating either GH, but then again we're sub-tropical here. Here's a link with some pix - scroll down to view them.

Here is a link that might be useful: Deck installation

Drainage can be managed. See the thread on the same topic from January.

Here is a link that might be useful: GH on a deck

Thanks everyone for your input. You have given me some things to think about before I make the final decision.