Prices of resale Housing Board flats inched up marginally last month, even as the number of units changing hands dropped.

There were 18.6 per cent fewer transactions last month - 2,076 units sold compared with 2,550 units in July, according to flash estimates released by real estate portal SRX Property yesterday.

But the drop is not unusual, observers said, given that August typically sees sluggish sales due to the Hungry Ghost Festival.

OrangeTee & Tie research and consultancy head Christine Sun noted two other possible factors. One is the 726 Re-Offer of Balance Flats the HDB launched at the end of last month, which may have drawn some demand for resale flats away. The other is that, in general, more flats have been sold this year than last, possibly due to the demand following the spate of en bloc sales in recent months.

Despite August's month-on-month drop, the number of transactions is still 6.1 per cent higher than in the same month last year, and above the monthly average of 1,777 units sold over the last 12 months. The total sales volume for the first eight months of this year - 14,404 units - is also higher than the same period last year ( 13,508).

Meanwhile, HDB resale flats were 0.1 per cent more expensive last month compared with July. This is 1.7 per cent lower from the same month last year, and 13.5 per cent cheaper since the peak in April 2013.

But overall, observers said, prices have been keeping within a 1 per cent range, in line with expectations that prices of HDB resale flats are stabilising.

Ms Sun added that the impact of more upgrading programmes and the Voluntary Early Redevelopment Scheme announced at last month's National Day Rally would not be felt until a few months from now.

Also last month, the overall median Transaction Over X-Value (TOX) remained at zero. TOX measures whether buyers are overpaying or underpaying compared with SRX's computer-generated market value. It is the company's take on cash-over-valuation, the premium paid on a flat's expected value.

Flats in Kallang and Whampoa appeared to be in the highest demand, with a median TOX of $14,000. In contrast, flats in Toa Payoh posted the lowest median TOX of negative $6,000.