Required topsoil for a lawn - experiences?

This is how it looks today.

If we manage that, we are happy!

If we manage that, we will be happy!

Not anymore in this dry summer.

We sowed lupines to loosen the soil.

I wouldn't start that anymore this summer either. A winter frost is needed in the clay soil. Using veld lupine is a half-good idea. Half-good because it really loosens and gives nitrogen to the soil, but removing it later in the lawn is tedious. Even a glyphosate treatment before sowing often doesn't eliminate lupine. It roots deeply.

... there are also annual lupines. You should plant them, they also suppress weeds. Clear them later. Everything is fine then. It has not come back with us.

Ok, I didn't know the one-year-olds.