Best Greenhouse base?

Good morning Folks,
I am in the process of re-siting my aluminium greenhouse. Previously I just put the base on the ground but because it wasn't plumb it didn't sit well. Also the height of the greenhouse wasn't very satisfactory, not allowing me to fit shelving. So now I am going to put in a proper strip foundation (nothing too substantial), build a couple of courses of bricks and site my greenhouse on that, thus levelling it up and raising its height.
My question is this; what is the best floor for a greenhouse?
I have been using some decking I had spare which worked ok but debris would fall down the gaps and sides which I think contributed to diseased plants.
So would a concrete slab be best or open beds with a solid strip down the middle.
Any comments would be appreciated.

 

Hiya Dave.

It's about pros and cons. With a greenhouse border you don't have to be so fussy about watering and it's so much easier to water. On the other hand, you'd have to change the soil every couple of years to prevent disease build-up. With Grow-bags (concrete base) the watering can be problematic, I've found. If the compost isn't kept wet and allowed to dry out on the surface, it can kinda 'glaze' over, so that when you water, it just runs round the sides. But, on the other hand, there's no soil to change. I suppose there's also a cost issue. The cost of Grow-bags against the cost of soil (if you have to buy it in), also the cost of the concrete. I opted for a border, it just suits me as I'm not the most fastidious of gardeners No doubt others can add more to help

Cheers...Freddy

 

I put about 3 layers of weed membrane & then widely spaced slabs with gravel infill in the gaps in mine - works well to allow over enthusiastic watering to drain & keeps weeds away. Time will tell if the invading bamboo from next door will be defeated. The only real problem with that is the ants which seem to get into anything I put on the ground.

I do keep a rubbish bucket in there for unnecessary bits of plants & dont do any potting on etc to avoid too much mess - but then Im a messy gardener.

 

I have two greenhouses. One has open soil borders, and I use that as my "cropping" greenhouse. The other is the "propagating house" and that only has plants in pots, on benches, and that has a paving brick floor, laid on sand with good quality membrane under it. I too have ants living in the sand, but the weeds that germinate there don't have any umph and are easily pulled out. I too do not do potting etc. in the propagating greenhouse to try to keep the floor clean. The staging benches are solid rather than slatted (actually they are covered with capillary matting for irrigation) so generally no soil falls on the floor.

The base for both greenhouses is concrete footings with 2 courses of bricks. I wish I had used engineering bricks as some of the ones I sued have crumbled in the frost.

I dug the floor deeper in the cropping house, to prove more heigh-to-eaves.

 

P.S. Angle your base slightly so the gutters "fall" towards the end where you want a water butt, and perhaps put a reasonable diameter duct "through" the footings that you can run water / electricity etc. through later, if you need to.

 

Thanks for everyones input, I guess it boils down to what I'm going to use the greenhouse for. I've been so disappointed with my tomatoes this last couple of years I feel like giving up on them and just concentrating on bedding , container & pots plants. Just an additional thought, would a concrete slab act like a storage radiator, heating up during the day and releasing it at night?

 

Yes, but not enough to make a significant difference in Winter - there ain't enough heat in the sun in winter, but every-little-helps. You could consider using a small fan to "blow" hot air from the ridge of the greenhouse into a storage unit under the floor (something that will retain thermal mass - broken glass will do) and then reversing the fan at night.

Dick Strawbridge (Self Sufficiency guru) built something along those lines, Mr Google will no doubt find the details

I think mine were a lot less work when I moved to planting them in greenhouse borders, instead of in 12" pots (which I had to water at least twice a day). In the border I now only have to water them every other day

 

Here`s the strawbridge design but i wouldnt expect too much from it
http://thesoulpatchblog.blogspot.co.uk/2011/10/solar-panel-powered-heat-sink-for-your.html

 

Thanks for the link, most intriguing! This simple exercise is now developing into a serious engineering project! All I now need is permission from the relevant authority (the wife), a supply of crushed glass (raiding the neighbours bottle recycling bins) a fan (didn't use the computer much anyway) a deep cycle battery (brothers caravanette) and a week or two off work. Eat your heart out Brunel! (Now where did I put my hard hat?)
Seriously I do appreciate everyone's input, thank you.

 

I don't think there is any way around:

Insulate as well as possible (bubblewrap usually, taped so there are no gaps). Insulation is the cheapest form of "heat", so to speak.
Provide a source of heating

I read of magical solar-glass, and heat retaining This & That. They may all contribute something but my solar collectors (for the house) collect 10% of the power in Winter that they do in Summer. Its not enough to do anything useful with, and we get many days on the trot when they collect Zip. We do sometimes get cold days that are bright and clear, so whatever is collected can offset the extreme cold of clear-sky nights, but don't be fooled into thinking that you can heat a greenhouse in Winter from the sun [in the UK] - if you could everyone would already be doing it

 

There`s barely enough sun to heat it in the summer these days
David, before you go raiding the bottle banks consider the soil under your greenhouse will have more heat capacity, no transport cost and you dont need to bash it with a hammer.
You may want to do some testing before you start digging , put a pc fan at one end of an 8ft length of 38mm wastepipe and see how much makes it out the other end

 

There's a guy on another forum who did something similar last Autumn. He reported good results in the Autumn, but I'm not sure he has updated with what the benefit, if any, was during the Winter. I'll ask him for some feedback and report back.

 

He has said that for him it was a mild Winter and his heater (set to frost free) hardly came on at all, so subjectively he thinks it helped but no concrete figures.

His heat sink is a pit of gravel (under his greenhouse floor)