Earth drill for point foundations - which diameter is good?

We want to make point foundations for a log wall fence and a chain link fence as well as for a greenhouse. However, I don't want to dig them all out with a spade, and a motor-driven earth auger is too expensive for me (even to rent). Therefore, I would like to use a manual auger. What size is sufficient here? Is 20cm diameter enough? There is a version from Fiskars that I am a bit interested in. Otherwise, I also have 25 and 30cm diameters from different manufacturers in my shopping cart. What do you recommend?

And should one insert KG pipes into the holes, or would it be better to pour the concrete directly into the ground?

Hi,

a 20mm bit is more than enough for posts, and it should also suffice for the pad foundations. However, I advise against the manual version, as you'll quickly lose interest unless you have pure sandy soil. It's no fun, so better buy a cheap one with a motor; they usually come with 2 or 3 drill bits for the front.
Concrete directly into the ground provides more stability than the version with the pipe in your case.

Thank you for the reply! That sounds good. I have always read about 30x30 or 40x40 foundations, but that probably applies more to carports, patio covers, and other large things? However, it could well be that after receiving the cost estimates, we might prefer to do it ourselves... I am still undecided about the motorized auger. On the one hand, the Fiskars manual earth auger has really great reviews, on the other hand, I don't like these noisy, maintenance-intensive gasoline engines. Are there good electric versions? Or are the gas-powered ones better?

Hello Changeling

Google "Lochspaten". I find it better than a hand drill.

Steven

I have looked into it, but I am more convinced by the concept of the drill. The [Lochspaten] seem cumbersome, and I can imagine that beyond a certain depth you can no longer work nicely with them. Especially in somewhat harder soils. Why are you on the [Lochspaten] side?

An electric version would be new to me, why would it be, these things are mostly used in agriculture or landscaping, where there is not always electricity available. What kind of maintenance should be required for your 50 holes? Put in gasoline and off you go. Buy a device for €250 and then sell it again on classifieds for €180 and you're done.