The facet is a new instance per chunk:
HouseFacet houseFacet = chunkRegion.getFacet(HouseFacet.class);
E.g. for a chunk with the region Min: (-64, -128, -32), Size: (32, 64, 32))
you get a facet with Min: (-68, -136, -36) and Size: (40, 72, 40), because the HouseProvider requires the border...