I have a question about lumpy lawn. This is the second time I have laid my lawn (rolawn turf) as the first time round it ended up patchy and dead in places within a year. On the second attempt I made sure I dug and turned the subsoil pretty much down to about a half metre and I've been careful not too use too much nutrient supplement. This time round I actually exposed some old shallow foundations which I removed as figured these might have been the cause for the first failing. On the reworked subsoil I removed cobbles and hard fragments and then placed 20 cm cover of certified lawn topsoil (sandy loam). I laid a Rolawn shade tolerant single species grass on a level surface according to their instructions. I watered daily and all seem fine.
Within three months though I noticed that the lawn had become patchy and lumpy to walk on - I doubt it will last much more into the next summer. Now I wondered if this was clay heave since the natural soil beneath Made Ground and Topsoil is a very good clay. There are also a few big trees nearby and I wondered if the shrinking a swelling of the clay was resulting in heave?
I also thought the subsoil may be contaminated since it has foundry waste within in (slag and clinker). However I did apply a clean topsoil cover and so I would be surprised if the contamination theory would occur so quick/
Anyway would appreciate some advice as I doubt I can face another attempt at turfing the lawn and am contemplating wood chipping the whole lot or investigating artificial lawns.