Renovating a lawn - how?

A colleague has asked me to help "repair" her lawn. Lawn care is one part of gardening I know absolutely nothing about. I have never even had a lawn myself. Where should I begin? The existing lawn is weedy and full of overgrown grass. Should this be trimmed with a mower first, or should I scarify, or start straight away by laying down weedkiller, or dig the whole lot up and toss it in the compost bin? If there are individual weeds I suppose they can be dug out with a trowel? Then I suppose I can dig the area over, before scattering the new grass seed, or laying turf?
Suggestions are appreciated!

 

Part of the answer depends on what is there now. If the grass is a coarse varietynot suitable for a lawn then it could be better to dig out and start afresh.

However it is surprising how some TLC can bring old grass to life. I would do the following.

1. Mow the grass. I would recommend a rotary mower set initially at the highest setting and then reduce the cut hight until you get as low as feasible. Bumps and hollows may stop you getting down to the lowest setting.

2. Water on a lawn weedkiller (3 days after mowing). Then just mow the lawn weekly (start 3+ days after weed treatment). Hint - I mark out the recommended dose area with flour, its cheap and disappears quickly.

3. Sort out any bumps and hollows. Bumps - cut an H shape into the grass with a spade across the bump, peel back the grass like lifting a turf, and scrape out the earth so that when you replace the grass the bump has gone. Hollows - fill with a sieved earth/seed mixture. Water both to promote growth.

4. Scarify. A power scarifyer will remove an amazing amount of thatch and moss and will frighten you as to how it leaves the grass looking - don't worry. Afterwards cut on a low setting to tidy up and hoover any leftovers.

5. Feed. Water or sprinkle on a lawn fertiliser regularly. This, together with regular mowing will promote new growth and thicken up the grass cover.

Annually, scarify and treat any weeds. Keep feeding the grass but not necessarily as frequently as the instructions may say, I would say monthly. Consider leaving the grass slightly longer in areas of heavy traffic.

 

Thanks for this answer: haven't been on this site for a while but on checking now I realised you had posted this very informative answer to my question quite a while ago. So - thanks!