Most art deco houses were built with good subfloor ground clearance – generally 20” (500 mm) or more. But there may be situations where there is insufficient clearance, particularly on sloping ground. A lack of ground clearance may not be a problem as long as the soil under the house is dry and there is sufficient ventilation.
Minimum ground levels can be addressed by sloping the site around the perimeter away from the building so that water does not drain underneath it.
Trenching may be necessary to achieve access to the underfloor space.
If an extension is proposed where the existing floor level is lower than permitted under a Building Code Acceptable Solution, but there is no evidence of damage from subfloor moisture, apply to build to the existing floor level as an Alternative Solution and specify timber with a higher level of treatment or natural durability.