Trying the v.clean command and checked the layer with Topology checker and it turned out every single geometry was invalid.
What to do now?
I have two shapefiles with 3D building blocks that I want to merge (Both MultiPolygonZ-type, the same columns in attribute table with the same projection). The blocks represent houses in two different area of the city (no overlaps).
Vector > Data Management Tools > Merge vector layers works great except that some features in the merged file looses it's solidness, see example below:
Houses from one of the shapes before merge (all houses are solid):
Has anyone experienced the same problem and been able to workaround it?
Links below to two of the shape-files I'm trying to merge if anyone want to try and re-create the problem: