FNB said on Friday that its property index had shown strengthening demand for the fourth consecutive month.

The FNB Valuers Residential Market Index rated demand for property at 46.1 in April, up from the previous month's 45.8.

The strengthening resulted from a rise in residential demand, rated at 50.5. It was the first time this value had risen above 50 since December 2008.

This implied that market demand was "strong" rather than "weak" on a scale from one to 100, the bank said in a statement.

The index collects ratings from property valuers employed by FNB. Valuers are asked whether demand and supply of property in a specific area is "good" (100), "average" (50), and "weak" (zero).

Aggregate ratings are then compiled, FNB explained.

"FNB's valuers collectively perceived residential demand to have strengthened further in April, but still give a stronger rating to supply than to demand."

Valuers believe demand has been growing at a faster rate than supply. Despite this increasing demand, the market strength index remained below the crucial 50 level.

Above this number, the market would be healthier and demand would start to exceed supply. This implied that house price inflation -- as shown in the FNB House Price Index -- was not yet sustainable.

"The need for caution, with regard to near term expectations, is increased by the signs of a soft global economic period currently developing," FNB said.