Major lawn headache...pics inside

Recently moved house...has a large garden. A lot of lawn. Some areas of the lawn are just one mass of dead patches (what appears to be weed killer) and weeds everywhere

Here are some pics

share.pho.to/9iC8h

I have been trying to control them but to no avail. I'm a novice at this so would like advice on what to do to make the lawn look like...a lawn! Thank you

 

Dead patches can be caused by several things. My simplest advice would be to cut the grass as low as possible.

Then scarify, remove as much dead grass and thatch. Reseed and ad some good quality topsoil.

Have a look at the following threads.

http://gardenerscorner.co.uk/forum/threads/operation-lawn-is-in-full-swing.96836/
http://gardenerscorner.co.uk/forum/threads/lawn-newbie-advice.97461/
http://gardenerscorner.co.uk/forum/threads/can-i-scarify-again.102884/