RTS Style : Navmesh into a grid to make buildings

Hi there.

I have a navmesh with some navmesh agents and obstacles and it's working very nice.

Now I wanted to create a Grid on top of this navmesh to setup the buildings construction. I have some ideias of how I could do this, but not sure because my navmesh has different heights (some has 0, others 10, others 20).

How could I solve this problem?

Thanks

Could you attach a nav mesh obstacle to your building game objects?