DIY concrete for a small concrete pad / footpath section

Panda

I'm planning to build a lean-to greenhouse to an existing small brick built shed and have some questions. Approx. dimensions 4ft x 9ft - 1.2m x 2.75m.

Example. (but not buying a kit) https://www.buyshedsdirect.co.uk/8-x-4-mercia-traditional-wooden-lean-to-greenhouse

Mine will be using transparent corrugated plastic on the roof and 2 sides. The back will be corrugated metal to reflect a bit of heat/light instead of letting it through.

I know what I need to do to make strong concrete footings for the posts so I'll do that first since it's much deeper and they will be a bit higher than the pad. Once that is set and dry I'll do the pad underneath afterwards. I've watched countless videos on youtube but it's mainly DIYers from the US and they all seem to get cement mixers or delivered by truck. Many use Quikrete which is a premix of sand cement and aggregate.

Lot's of these youtubers are also doing a method of "Dry-pour" of this Quikrete where they just empty the bags out on the prepared area, level it and then wet it regularly to set the cement. This seems really beginner friendly so I'm wondering has anyone here done this? Is anyone aware of a equivalent of Quikrete in Ireland? I see there's lots of rapid set bags for posts, but I think those are slightly different. I could be wrong though.

For a section of this size, I've read that the pad should be 4inches thick and that I should include an expansion joint in case of cracks. I'll also likely use some metal wire for strength but not sure if the typical rebar would be overkill.

10-10-20

Hi! Yes, we have the same product here just a different branding:

https://www.goodwins.ie/products/k-post-setting-cement-20kg.html

You can try do a dry pour for the posts, it's not a critical that the concrete sets in a uniform manner as its not load bearing like a slab, but i'd follow the instructions and do it wet myself.

4" is sufficient for low traffic but i would definitely do a wet mix here. You can get a mixer for a weekend for a few euro. I don't think it needs expansion joints here though. Rebar also not necessary but if you had some rebar mesh then use it.

Read up on pouring, finishing and curing concrete, it's a science!

Panda

Hey, thanks for the reply. I've used a rapid set postmix before and it was indeed very rapid so I thought there might be some other additive in those bags but then Quikrete is also clearly supposed to be Quik.

I'll definitely do a wet mix for the posts just using sand, cement and gravel. I'll probably do 3 posts along the length of the space and I'm not in a rush so will probably mix a new batch of that each time.

After the posts are pretty much set I'm mainly wondering about doing a dry pour of concrete for the pad underneath the lean-to. Like I mentioned already I've seen videos where people do a full shed base using this method and while it might take time to level it off I would avoid having to mix multiple wet batches of concrete in a wheel barrow or rent a mixer.

One other part I'm not sure about is the connection between the pad and the shed, do I need to put some sort of divider (plastic or other) between the two to help to stop any dampness creeping in from the pad?

Here's a rough drawing (definitely not to scale) of what the area is like. It doesn't show the posts or the frame of the lean to, and the pitch of the roof will probably match the pitch of the existing roof.

Another issue I have is that as you can see in the drawing the garden slopes up towards the back. I've already dug into the ground to make a level pad but that means I also probably need to build a small retaining wall. The ground is incredibly rocky and the further I go into the corner it's also very sandy and heavily compacted. I don't think it will move much but very hard to know.