Houses may be connected with a stretch of roof called a connection. Only houses that are relatively close together with parallel roofs can be connected correctly.
To connect two buildings
1 First start a connection either from the House dialog box 
or just after adding a house 
2 At the "Point within house" prompt select a point inside on the roof of the first house (1 in the diagram above)
3 At the "House edge" prompt, select the edge of the first house, nearest the second house. (2 in the diagram)
4 At the "Next house edge" prompt, select the edge of the second house (3 in the diagram)
5 At the "House width[default]" prompt, either select another point, right click to choose the default width (previous) or type in a width.
