Trowellable roof pitch.
Made by Ormonoid, buy it at Mitre10. Just pour it in the gap.
It will seal hard enough to take the garage creeper.
Will stay soft enough that it won't push the slabs apart.
And. It's totally waterproof.
Hey, I just think I've found a way to seal every Series model Landy ever built.:D
Pour Ormonoid all over it.

