I live in a new build, so there for my underneath my grass is nothing but bricks and rubble. Nothing tends to grow very well, anyone got any advice, apart from rip it up and start again??

sadly i think in the long run you would be better off removing the rubble and buying some decent topsoil. too often it is subsoil [poor in nutrients etc] that is used before grassing over.

think of it as a means of designing the garden you want ie beds/borders etc.

more experienced in the matter of lawns might give you better advice. I leave the grass/moss to husband.

Sadly it is al to common that the builder lifts off the top soil and sells it before starting to build. Dumps all the rubble across t he garden and covers with thin layer of subsoil which is then grassed over. As Seaburngirl says the only real solution is to get rid of the rubble and bring in some topsoil...

Alternatively you could try some raised beds. Modern construction I'm afraid