Paving greenhouse floor

[Adrian]

She's finally accepted the obvious, and decided that the packed earth floor in the greenhouse is not the best of surfaces, and that laying some flattened cardboard boxes down will not prevent the trees that were in there from growing back - nor will it slow the ants from building nests...

And, of course, in the spirit of such realisations, it is now my high priority.

Yesterday saw much of the earth dug out. Today, I'm going to be procuring paving slabs, sand and cement.

The plan - so far - is to lay a bed of sand down, then weedproof membrane. Then a layer of sand, sand+cement, paving slabs, "grouted" with sand+cement.

Sound about right? What sort of layer of sand? Just enough to get it all level plus a little bit? Or more?

Roughly how much sand and how much cement should I be getting? It's about

4m2 of floor.

[Martin Brown]

Strikes me that you are making a lot of work for yourself. I have always found a paved path of 3x2 down the middle and a thick mulch of pebble gravel under the staging is plenty good enough. Weed proof membrane under it if you must but I never bothered. One side was left open soil for growing things in the require a deep root run like grapes.

I really wouldn't use cement. YMMV.

My suggestion would be some coarse sand, enough paving slabs to go down the middle and a largish volume of gravel.

[Adrian]

Entirely feasible...

Yesterday's prep involved removing some very, very heavy duty weeds - the house was empty and the greenhouse totally unloved for five years. As a result, last year's initial prep involved cutting trees in it down. The trunks were coming up several inches thick, and cutting them down at ground level and covering them didn't even make them blink. I've dragged quite a lot of thick trunks and underground runners out, but I can't guarantee there aren't more waiting to say hello. I'd really like them not to... The greenhouse's sides sit on poured concrete rim that doesn't seem to go down far enough to dissuade the triffids.

Oh, yes - then there's the ants. Two LARGE nests (hopefully) destroyed yesterday, and plenty of others elsewhere in the garden.

Ta.

I did suggest gravel, she's not keen - think it's going to be more work to keep weed-free, even with membrane/sand underneath. Since slabs are so cheap, I figured easiest to just do the lot.

Her plan is not - currently - to have anything planted directly. The earth that's there is so dry and sterile that I can't see anything thriving anyway. OK, we could dig plenty of compost in, but...

[fred]

And you get the benefit of any runoff from watering simply draining into the soil. But somehow I get the idea that these recurring roots might laugh at weed membrane.

[Tim Watts]

It would work. Only need 6:1 dry mix to lay the slabs on (water gently from above after you get the whole area done and right).

[Adrian]

Yes, that's occurred to me, too...

[Tim Watts]

I'd be happy personally with nothing but weed membrane and some stone chippings or 20mm pebble aggregate - they do not move that much when walked on.

[Martin Brown]

That is pretty much what I had to do in Belgium, but my greenhouse there was a lot bigger 10m x 30m with trees growing through the broken roof. Took most of a year to make it serviceable again. I never did get the horsetails under control but simple managed them.

I would definitely not try to concrete slab over these heavy duty weeds until you have gone one season without them recurring. Basically hit them with weedkiller ever time a green shoot appears and or apply rootout to the stumps. If they are as you describe you will end up with weeds laughing at the weedproof membrane pushing up your paving slabs.

If the habitat is right ants will always be present. Live and let live they don't really do any harm.

Gravel under the staging and slabs to walk on works very well.

[Adrian]

Thanks. I'll point that out to 'erself.

[John Rumm]

I would go with a sub base of type 1 mot rammed down hard - a couple of inches will do. Then 25 - 40 mm or so of sharp sand with some cement added (used dry). If the slabs you are using are of consistent thickness then you can lay the weak mix all over the area, screed it off level and chuck the slabs on top. If they are variable thickness, then you can bed each one individually - adding / removing sand as required.

I would say about 16 bags of type 1, 12 bags of sharp sand, and 1.5 bags of cement.

Elephants foot or a plank and a sledge hammer for tamping it down.

No sure I would bother with a weed membrane - limestone chippings and slabs are pretty impermeable - especially when compared to plastic / fabric.

[damduck-egg]

That is what we have but it is only a small 10ft by 12ft greenhouse. Depth above membrane about 3" Did it that way as can leave a water mist on when it gets very hot and the pepples absorb the excess where as slabs would just get puddles or run it off. The Chippings then do some cooling as the water amongst them gets evaporated. It is a pain if you drop something like a small Ali fixing bolt but that doesn't happen often. There is the possibility that slugs and snails can live amongst the chippings if they get too contaminated by soil spillage but being a small area it is easy to spray some mild jeyes fluid over before things start to grown. Been down about 4 years now, if soil spillage eventually gets too much it shouldn't take much effort to shovel it out and use else where and replace with new or just chuck into the cement mixer and wash it in some water and chuck it back in.

G.Harman

[harryagain]

You can cut the roots and paint on some roundup on to the cut bits. Cuts must be fresh to be effective.