Artifacts everywhere after building light


I have some problems building the lighting in my model, the 2 following images are before building the lightmap, and one after.
This model was made in sketchup, the colours are simple so I can replace them here in unreal 4. (I know you’re not supposed to do furniture and the building at once but thats something for the next time)


The error in the bottom in the message log is “Object has wrapping UVs”

Where do I even start solving this problem, if at all?
The goal is to have the architectual visualisation of this building with realistic materials and realistic lighting.

Thanks in advance

Your meshes each need a second UV channel that will be used for lightmaps.
For those UV’s, they need to fit in the 0-1 UV space, and they can’t overlap: