We have an area of 45m2 to re turf. It was previously laid by builders on who added about 25mm of 'top soil' onto the poor quality soil/clay below. Over the years the lawn has settled and needs to raised by about 50 - 75mm all over.
The area is in a court yard and holds water in the winter and becomes dry in the summer.
My method to remedy the situation is to strip the turf and remove the soil to give a depth of about 100mm from the required top level. 'Aerate' the sub soil using a fork or similar and brush in some sharp sand for additional drainage and add topsoil (or should that be prepared loam?) and level, compact and turf as normal.
Am I on the right lines? Will it need 100mm of top soil or loam?
Simon
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Replies
I'd say a lot depends on what your client is prepared to pay for any how much flexibility you've got in the specification and the planned level of maintenance afterwards.
If it's a lawn that'll have lots of traffic or ball games played on it then a 10mm screened soil will often suffice.
However, one of the problems with much of the 10mm screened (at least in my landscaping area) is, it is collected from disparate locations within a truck drive from the yard where it is mixed and then distributed from so it's not possible to accurately classify it.
It's not impossible to import a host of pernicious weeds (including Japanese Knotweed) with the soil. Some soils can also contain high levels of subsoil too. It's probably best to import certified soil from a known source.
Loam is a mixture of sand/silt/clay.
Loam is good at retaining nutrients but if it has too high a clay content then it'll compact too hard (think cricket square or tennis court). If it's too sandy it'll drain too fast and the grass roots will struggle and often shrink to the surface if there's little or no irrigation in the summer and if it's too silty the surface of a lawn might become impermeable to water and air because its particles are too small to penetrate.
My preference would be a sandy loam.
Why not talk to the guys at TOPSOIL (they are exhibiting at Creating Landscapes).
I'm sure they could advise on your particular requirements.
One important aspect, of which you mention, is the poor sub-layer. Breaking through any compaction pan is essential for the long term success of your proposed new lawn.
In some instances it is beneficial to ameliorate the soil greater than 100mm but what you eventually decide goes back to budget, specification and the freedom you've been given by your client.
Hope this helps a bit?
I would go for 6" of topsoil/loam (dont think it will make a major difference which one unless the client wants a top quality lawn.
Its only a small lawn so once youve dug down install a simple pea shingle frence drain assuming there is somewhere for the water to drain away to or small sump/soakaway with sub-base laid to falls.
Any left over shingle can be lightly dug over into the sub-base.
Im not a fan of sharp sand and think it should be kept well away from lawns.
I agree with Jim. 150mm depth of soil is better.
I'd agree regarding depth of soil. 100mm is the minimum required but 150mm would be better, as the turf will put down quite deep roots. The deeper the roots, the more drought tolerant it will be.