On May 20, 3:28 pm, "Kroma" wrote:
Hi,

We moved in to our house just over a year ago. Parts of the garden were
overgrown including 2 bushed which had overgrown on to the lawn and killed

I added some soil and grass seed and it grew back nicely.

However, after all the recent rain the patches seem to have sunken by about
half an inch.

For a small amount like that over a smallish area you can probably get
away with adding an equal mix of topsoil and sharp sand at almost any
time of year. Anything more than about 1cm is best done in autumn or
early spring. I am gradually levelling out my lawn where a big tree
root is rotting away underneath this way.

Can I just whack some topsoil on top and hope the grass will grow through it
or should I dig it up and put topsoil underneath (then replace the turf of
course)?

If it really is only a half inch then you can probably get away with
it at almost any time of year, but if it is any thicker than that you
may well kill the grass by smothering it. Especially if it is a fine
grass. I reckon upto 1cm deep you can top dress and then leave the
grass to grow through again. A bit of feed mixed in may help boost its
growth provided you don't minf having a greener patch for a while.

Regards,
Martin Brown