When I first looked at it I thought it was obvious why it was built on a terrace. The ground between Mill Street Yates Street, Corn Street and what was once Beaufort Street is very uneven ground.

Yates Street is on a hill and the idea of the terrace was so that all the houses could be at roughly the same level.

Look at this Googlemap Image and count the number of steps at one end of Yates Street:

http://maps.google.co.uk/maps?f=q&so...102.09,,0,2.79

I count about 15 steps.



And the other end:

http://maps.google.co.uk/maps?f=q&so...63.36,,0,11.97

I count about 8 steps.

You can also see that Corn Street (the street next to Yates Street) has a terrace in it.

http://maps.google.co.uk/maps?f=q&so...65.63,,0,11.29

But because the ground naturally rised higher than in Yates Street, the terrace ends half-way along the road.

http://maps.google.co.uk/maps?f=q&so...18.83,,0,13.92

If they hadn't built the houses here on a terrace the ground floor rear-windows of Corn Street would've looked directly into the upstairs rear-windows of Yates Street.