Foundation for a garden house of 18 m2

Hello

This is a garden shed (approx. 3 x 6 m) that needs a foundation. The garden shed is practically standing in a field, and it is difficult to use large amounts of concrete. The ground is planned to be constructed with structural timber 12 x 12 cm (frame 3 x 0.6 m).

Now the question arises whether a "proper" foundation is needed here (80 cm depth) or if "concrete footings" are sufficient? If a deep foundation is required, then I can only imagine a point foundation (making holes with an earth auger and pouring concrete).

Thank you!

Then just do it like that. In principle, you can probably only say for sure with a soil survey. But for a garden shed, I wouldn’t go to great lengths. Just make two more point foundations, the holes with a nice diameter, and maybe even a bit of steel inside.

Thank you, I think this is the safest way. Which grid is recommended here? Of course, I want to make as few pier foundations as possible. My concerns relate to the beams for the floor of the garden shed, which can bend if the grid is too large. A little bending is alright, but not too much (the garden shed will already be somewhat heavier as it is insulated and clad with Rhombus slats).

Well, it probably also depends on the thickness of the beams. With 8x8 or so, I would have put 2 on the short sides and three on the long sides. If you want to use narrower ones, you might need more. But so far it's only theory for me, maybe a practitioner will chime in.

The beams are 12 x 12 or 6 x 12. Then it would be a grid of 1.5 m x 2. On the internet, very small distances (50 - 80 cm) are often seen.

I find that too much, but I have no idea either. Especially if the foundations are anyway 80 cm deep (diameter 20 - 30 cm).

Exactly in that example, it only makes four, right? Well, that will be smaller. You need the smaller distances if you want to lay the floorboards directly on the beam. They are usually not that thick and would otherwise bend. But you can just as well add cross battens over the support beams to reduce the distances. I am of the opinion that at 12x12 you don't need to worry, three on the long side should be enough. But I am not a structural engineer, not a carpenter, and have practically never done something like that. So take it with caution.