Do you remember the following illustration from the topic on the 4 Symbolic Animals?
The principle of a solid tortise or that the back of the house should form a `protective' barrier behind the house.
Large trees or a row of bushes/shrubs could be planted behind the house. This acts as a tortise or "barrier" behind the house. Avoid planting large trees in front of the house especially in the middle of the main door entrance as it blocks good Chi coming into the house. Another alternative is to construct a brick wall behind the house.
Make sure that trees and shrubs has to be regularly trimmed.