Once you have the correct dimensions,  it might be better mapped as building=roof + layer=1 + man_made=canopy (it doesn't really need the name tag, but you could put that in the description tag). If you're interested in the 3D representation, you could also add a height tag (height in metres).

https://wiki.openstreetmap.org/wiki/Tag:building%3Droof

If you'd like any help with this, please feel free to ask.