Posted: 24/04/2015 at 22:28
Some excellent advice here:
First thing - don't use combination treatment if you want to seed, apparently the worst thing you could do!
Did you scarify (using blades) or just rake well? I scarified and raked mine recently and the results were scary! either way you probably have started out right, I may have gone a bit too far.
Next thing is deal with compaction, cheapest option it to use a garden fork to aerate it, the website explains all the options though. It takes ages with a fork, and it seems that you should do it fairly frequently to be properly effective.
Next seed - you sprinkled it on and then what? Apparently it needs good soil contact to germinate so it is recommended to trample it in or use a light roller (I know seems counter-intuitive having just de-compacted the soil!) to make sure it is pressed firmly onto the soil.
After that it needs water and warmth - it won't germinate if the climatic conditions are still to cold, and I suspect this is why there is no evidence of germination on my overseeded lawn yet, although the initial flooding after I sowed it can't have been good. The good news is that the existing grass is coming back quite nicely, although slower than the weeds, so I'll need to deal with them once it looks lush enough to walk on again. I may also try overseeding again now the weather has improved.
If it doesn't rain you probably need to water it, I have finally bought a sprinkler and timer to help with this, but make sure you don't have a hosepipe or sprinkler ban heading into the summer.
Fertilizer is also a really good idea at this point, but not a multipurpose type. Use a straight fertilizer suitable for using with lawn seed, don't use moss killer, and make sure the dilution is right - over concentrating it will also be bad.
Lawnsmith seem to sell everything you could need, unfortunately I found them after I had already bought what I thought I needed....