Drainage

murnaghan9

My new build has a garden with just topsoil and mixed stone supplied by the builder. The centre of garden is quite  soggy, would grit improve this before I start seeding for grass.

Stevedaylilly

Unfortunately, new build properties are notorious for back filling gardens with brick/stone etc. To seed or lay a lawn you will need to carry out the same process and that is preparing the soil base before 
You will need to remove as much of the brick stone debri out of the soil prior to seeding or laying a new lawn. After that, you will, no doubt, need to top up with more top soil to fill in the voids 
The idea is to be able to rack the top soil, removing any big stones, then walking over the top soil to consolidate it. Then you take it again and go through the same process again untill your left with fine tilft ( a thin layer of 30mm soil without any large debrie in it) 
You are now ready to seed your lawn. Select a general grass seed or one for shaded area if required 

Lizzie27

There's been quite a few threads on here lately on the same topic so you may like to search on "drainage" and see what the others recommend.  Grit always helps in any event. 

murnaghan9

Thanks folks much appreciated