Rooftop gardening

[Richard on Maui]

I mentioned in another thread recently that I am about to move to the city of Honolulu on the island of Oahu (I'm going to have to make a new username I guess) and so I have been thinking about the different possibilities for a garden in the city.
The apartment building we are going to be living in actually has a flat roof, which I guess would make it suitable for gardening on... I have no experience of gardening on a roof though, and would welcome any comments from anyone with exoerience. The little bit of reading I have done indicates that it can be an extreme microclimate up on the roof, very windy and hot. I am more wondering about the challenges of doing it in way that doesn't damage the structure etc...
I guess I don't know if it is worth trying to convinve the landlord that it would be a good idea. I am sure I would face an uphill battle there. But you never know. They might be sympathetic. Anyway, what are the risks involved? Is it necessary to put some sort of material down that stops the organic matter from breaking down whatever the roof is made out of? Anyone have any clues about this?

[Jim Bob]

I'd recommend gardening in pots, you can put up shadecloth if it's too sunny. This also means less strain on the roof, as you tend to put more plants in a smaller space when using containers. And of course your landlord can't really complain if they're in pots, an hour or so of schlepping back and forth, a bit of a hose-down and scrub, and no-one will ever know there were plants there.

What kind of a roof-top is it? Is it a genuine roof, or a flat floor designed to be walked on? Are there any kind of walls there?

[hedwig]

in pots or whatever it is first a matter of static - does the roof hold all the weight.
If you want to garden directly on the roof you have really to involve a very experienced tradesman. There are several systems available. First the roof must be absolutely leek proven. Second the roots should ot grow into the roof waterproofing an extra layer is needed.This is certainly no DYO thing!
You risk to damage the whole roof if it is made false.

[barely run]

aquaponics would be the go......fully transportable.....
But due to my nomadic life I often grow in strofoam boxes....usually free from the veg shop. Fill with good potting mix and away you go. My herbs have been very sucessful, the lettuce....pick again types good, recently planted Cos... was a bit hot and they bolted to seed. the snow peas are doing great. Tomatoes....one plant ber bag of potting mix....plant into top of bag...drainage holes in bottom of bag.....also some sucess with hollow out lucerne bale fill with potting mix and plant...2 toms per bale
Bill Mollison video In Danger of Falling Food shows a balcony garden. Using trellis to expand grow area......it's an old video I got out recently from libary.
Last year or so there was a lot posted here on same subject oh and by the way......I container garden because I like growing stuff etc...but with cost of potting mix etc it's not cost effective....have yet to get 2nd crop from the same containers...lol
Would think one of those Bosaki things would be good for units

[heuristics]

Richard, you could be "Richard on Oahu, formerly known as Richard on Maui"!

[heuristics]

Pots.
I would expect it to be extremely hot and therefore things will dry out quickly. so you will need lots of water. Some plants simply wont take the direct heat. and the roof will have radiant heat well into the night.
If it is the top of an apartment block, maybe you'd need to be careful about high wind and things being blown off - shadecloth would need to be very well attached, even heavy pots could get airborne in one of those extreme tropical high wind events.

[Richard on Maui]

I haven't actually seen the place yet, except on a Google map... It looks like a flat roof. Don't know if the landlord will even give us permission to go up there yet, let alone garden on it. We'll see... If nothing else it would be a neat spot to put our solar ovens, so hopefully we'll be allowed to at least do that and have a couple of pots of herbs.
I like the name idea, Heuristics! Maybe when it happens, I'll become "the poster formerly known as Richard on Maui...", and eventually I can just use a symbol or something... :wink: Yeah, that's it. :lol:

[SueinWA]

You would have to use lightweight potting soil + compost instead of garden soil, due to the difference in weight.

Pots sitting directly on the roof may not be advisable; collect tuna or flattish catfood cans to use as 'feet' to allow air to circulate under the pots so as not to damage the roof surfacing.

Just a thought, but the roof may be stronger near the outside walls and above any loadbearing walls.

Sue