Topdressing a lawn will reduce minor hollows and undulations. A 50:50 topsoil/sand mix is usually used and smoothed out with a lute or dragmat.
Undertaken in the Autumn, several applications may be required over a few years to reduce severe hollows. Contrary to popular belief, rolling will not level an existing undulating lawn, it will just make the hollows deeper. Following heavy topdressing, new seed will need to be sown to create a partial new sward. With a thin topdressing, the existing grass is usually strong enough to push through without being smothered.
Please contact me if you would like additional information about lawn topdressing in Wells, Somerset.