I live in an area that has tonns of clay in the yard. Lots of roots too (huge, beautiful trees!).

When it rains, you can slide all over the place on my lawn. My lawn also had small bald spots - I guess from my dog running all over when it's wet.

I've planted grass seed and it seemed to start off well, but then 1/2 way through the summer it was just like before. It looks fine when the grass is longer.

How can I improve my grass without laying sod? I've been told I have to dig up the top 6" of my lawn and put down proper soil (urgh) or lay sod. My yard is pretty big so sod would be pretty expensive.

Any suggestions?

It is party shady in my yard because of all the big trees.

Any help would be appreciated. PS. Zone 4 (I think - southern Ontario)