To achieve a successful result with a grass lawn there needs to be sufficient depth of topsoil to hold enough moisture during dry summer periods to keep the grass green and healthy and also to absorb excess rainfall during wet periods to avoid standing water. Sometimes drainage is also necessary where the subsoil base is of high clay content or the area has no fall to aid natural runoff. The top-soil layer must also be of consistent compaction to avoid soft areas that settle or over-compaction that prevents the grass seed or turf from taking well - this is best achieved with healing by foot. Fine hand raking then creates the fine tilth required for grass seed to establish successfully.