If the area that is to be prepared is already an existing lawn then you will have to decide when the cut off point is for its current use.
It is a common mistake to leave it late in the season and then wonder why the turf or grass seed has not taken well - home-owners try to squeeze the best out of the summer before ripping out the old lawn.
My advice would be to prepare early enough so that your new lawn has the opportunity to establish itself before the very cold weather.
At the end of the summer, soil will continue to radiate back the suns heat that it has absorbed in the previous weeks. The optimum soil temperature for good root growth and grass seed germination is about 20 degrees.
Leave the preparation too late in the year and grass seed will not germinate properly or at all and turf, which needs to continue to grow so that it can take up water and nutrients, might never connect properly with the soil and extend its roots deep enough before going into the winter.
To weedkill or not?
It is a dilemma faced by many gardeners. Do I use chemicals to kill off the existing grass or do I remove the top surface and top up the levels with some fresh top soil?
Irrespective of your opinion of using chemicals, there are a number of factors that need to be considered about how and what should be done to give a lawn the best start possible.
The first consideration - why has the lawn failed in the first place? If your problems stems from poor fertility, drainage or there is a good poor root zone for the the grass to grow into then undoubtedly you need to improve the soil condition.
If you decide that the soil is poor, then slicing off the turf and composting it down is an option and it will avert the need to use chemicals.
Once you have sliced the turf off using a spade, turfing iron or mechanical turf cutter - well worth hiring if you have more than 30 square yards to do - you will need to turn over the soil below - NEVER add top soil directly to the existing compacted soil and seed or turf directly to the fresh soil.
Part of the reason for replacing the grass could be tiredness caused by excessive compaction. Adding soil looks good, is therapeutic as a quick solution but could be masking a problem that needs to be addressed if you new sward is to have a decent chance of rewarding you in the future.
Double digging is a great way of opening up the soil but be aware that you have sufficient and suitable soil at a decent depth. The last thing that you want to do is bring any gravel, clay or builders waste to the surface and replace it with your decent soil at a depth that is unattainable for normal root growth.
A rotovator is a good way to prepare large areas without wearing yourself out or breaking the bank. Be sure that the blades are working at sufficient depth to open up the soil.
If you determine that your garden soil is deficient in both nutrients or sufficient depth then it may be necessary to 'top up' the levels.
Avoid buying 'as dug' soil just because it is cheap. 'As dug' is a pseudonym for soil (possibly sub-soil) mixed with stone, builders waste and other rubbish. You could open up a can of worms and increase your workload tremendously. As dug soil is fine for filling in deep holes or bringing up levels as long as you intend to finish off the growing area with 6-12" (15-30cm) of quality top soil.
Look for screened top soil and better still, find a topsoil supplier who conforms to the Specification for Composted Materials (BSI PAS 100). Ask to visit the yard and inspect the soil where it is produced and, if possible to see the production process and to see how the soil is stored.
Rolawn are a national turf and top soil supplier and they supply soil in one tonne bags, which can be off-loaded by crane or if you have a need for large quantities, loose loads can be delivered in a tipping truck and unloaded in convenient spots to suit.
Quantities of soil you need to import depends on the state of the sub-soil area and existing soil that you are dealing with and how much you need to bring the levels up. If the existing soil is poor then consider stripping off the existing surface and remove it from site. Bring up the levels with good quality screened soil at a minimum depth of 15cm (6")
Spread and rake the soil out to your required profile and tread to firm it down. Rake out further until you are happy with the levels after which you are ready to lay your turf or broadcast your seed.
For more on turf laying see these related articles.
Buy soil online at Online Turf and Rolawn