as the food supply goes up in price with the costs of fuel.
Hydro is the way to go
I have an experiment in the garage.
come take a look.
Ray

Here is a link that might be useful: wasserhund

I like your site very much Ray. Your raft looks to be net pots in a tub with a large air stone to keep the water filled with oxygen. That's a lot simpler than using a bubbler to pump up the nutrients. I had pretty good luck with something simular, but on a bit larger scale some years ago. I used a childes swimming pool and cut out holes for large styrofoam cups in a floating styrofoam sheet. Good work there. Now I'm in a ret. trailer community, so your system might be the ticket here. I would recommend covering the clear plastic resivoir with aluminum foil or something to block the sunlight to prevent algea if it becomes a problem. chuck

Here is a link that might be useful: some old pix of float garden

Grizzman, I love the vertical growing tower. I have been toying with the idea of a new vertical design where a plastic tarp is hung up folded in two with a drip head at the top made from a long 1/2 inch pvc pipe drilled with holes. The nutrient drips down inside the tarp sheets to the bottom fold where it runs out into a tank with a return pump. Holes in the tarp on both sides hold foam rubber sockets for the plants. Chicken wire on each side of the folded tarp support the weight of the plants. Probably only good for leaf lettuce. My lettuce wall project?. So many possibilities. Thank you very much for the interesting link.

Those vertical farms are going to start becoming reality soon. It's a really popular idea and it's just a matter of time before someone with a lot of money and an urge to get their face on the front page is going to pay to have one built.

Look at how big being "green" is for some of those Hollywood stars. IIRC they're actually in the planning stages to build some 40-story vertical farm in Las Vegas.

I think it's incredibly irresponsible that we've allowed ourselves to get this dependent on transportation. People just don't realize that the average North American city has within its borders only enough food to feed the population for a few days. Without the constant influx of diesel-burning trucks with food, we'd starve in short order.

That's just ludicrous. It's insane when you realize (as we do) just how easily every flat rooftop could be converted to fresh vegetable production year-round. Top it off with a greenhouse roof, use waste heat from the building below to keep it warm in the winter (and, by merit of being covered in plants rather than tar, it would keep the building cooler in the summer)... if every major city made a commitment to stop WASTING all that space we'd save so much fuel that the price of gas would probably drop like a stone.

And personally, I'd love a job at a roof-top hydro farm. Just me, the plants, and the machines.

There's a lot of interest in roof-top gardening in this country, basically because of rampant theft. In this country, people wake up finding their entire garden looted.
There's more chance of securing your crop on a roof-top than in your back yard.

The only problem with substantial rooftop gardens on existing buildings is they're not designed to carry that much weight.
Its not impossible to retrofit them for the extra weight, but its not cheap either.

Given that we're discussing hydroponics it's funny that you'd worry about the weight. A soil farm would be the real concern to a structure.

Picture this: Primary nutrient tanks stored at ground level with solar-powered pumps used to top off smaller (but still sizable) reservoirs strategically positioned over the best load-bearing structures of the building. This could then be pumped out to the plants that need it in standard hydroponic grow bags and such (light-weight stuff).

The reasoning here is that ground-level tanks don't weigh down the building, are more easily accessible to larger equipment, and if buried would even help keep the temperatures more ideal.

Reservoirs on the roof allow for smaller pumps to handle the distribution to plants (since those pumps wouldn't be required to support a 15-20 foot head).

Additionally, the buildings could be topped with plastic sheeting like an inflatable greenhouse.

Given the amount of weight that the building has to be able to support simply in terms of roofing personnel and equipment for routine maintenance, I don't really think there's a lot to worry about.

Older buildings would probably need an inspection at the very least to make sure it's safe, but your average strip mall or supermarket would be in good enough shape to handle a couple tons of evenly-spaced goods on the roof.

Plus, they wouldn't have to worry about wind and rain damage to the building's roof anymore.

I believe you're thinking smaller scale than I am. I'm not talking the guy who puts a system on his apartment rooftop to stave off growing food bills. I'm talking entire building roofs working as functioning farms to maximize food production.
No way you'll see a system weighing in at less than 5psf.
You also might be surprised to know that most strip mall and shopping centers are designed to carry a minimum amount of rain and snow water and some positive pressure from wind events.
Concentrated equipment loads are normally specifically placed and accounted for in that location only (no broad encompassing extra load placed on the entire roof)Personnel loads (to access equipment) are negligible compared to the design snow loads.
Could these buildings actually support the extra weight? Probably under 99% of the daily circumstances, yes. Will a building code, building inspector, or engineer let it slide knowing they'll be held accountable when that 1% hits? Not likely. I know I wouldn't.
Actually older buildings, maybe 50+ years old, are more suited to this kind of retrofit because the materials they used back then were more robust and forgiving. its easier to get numbers to work in them.
I'm not saying its impossible to make that kind of system work; just that you're either underestimating the weights of the system or you're overestimating the fudge factor designed into most buildings.

You may be right on that, but I'm skeptical that it's as bad as you say.

IIRC, some cities are making big strides in this direction already. I think I read something about Chicago or some other northern city like that going through a really ambitious rooftop project like this.