Here’s a quick example including source files:
http://www.mediafire.com/download/p41dtw8w89yq519/house_example.zip
I only built a lightmap UV for the house itself and didn’t bother with grid alignment.
Didn’t even build a collision mesh and used per vertex collision instead, which is ok because of the simple geometrie.
For windows, doors and placeholder Props i used the lightmap and collision generation of UE4.
Usually i would do most of it with UCX_ as child objects of the mesh.
Ifv you’re interrested in how this is supposed to work, here’s another example i made a while ago:
http://www.mediafire.com/download/l4deifut24cby1o/housebuilder_new.zip
The first Example is done for indoor purpose only, this means all the faces of the outside that cannot be seen from the inside are scaled down heavily to save lightmap space.
In the other example this applies only to the top and bottom face of the outside, so these are scaled down.
Usually there would be a second level or roof above and something below the mesh, too.
Either do it like i did in the example or delete the top and bottom face completly, since they will never be seen.