While the original villa may have sufficient clearance, it is common for the clearances to be significantly less under the lean-to addition (particularly on a site that slopes to the front of the house).

A lack of ground clearance may not cause a problem, provided the soil under the villa is dry and/or there is sufficient ventilation.

Renovation options to address lower than minimum ground levels can include: 

• reshaping the land around the perimeter of the building to slope it away from the building so that water cannot drain underneath
• if the building is to be repiled, considering lifting it to increase clearance
• a concrete floor slab laid over a DPM
• incorporating a change of level into the planning of the addition
• getting permission from the BCA as an Alternative Solution to match the existing floor levels, but specifying timbers with higher levels of treatment or natural durability and covering the ground with polythene to reduce moisture evaporation into the subfloor space. 

Related links

Villas: building form