The house at 14 Sherlock Street, Kaleen, built in 1978 and vacated by an elderly woman, was the 23rd to be demolished by Shaw Building Group, which along with Manteena, has done the first tranche of work.

Shaw director Roger Poels said the Sherlock Street home was typical of many – a straightforward brick veneer single storey home, but some were more complicated, including double brick houses for which the removalists had used plastic sheeting to cover the outside while the outside wall was removed to clear out asbestos.

The amount of fluffy asbestos insulation had varied from "very very little" to "clumps the size of your hand", and on average there had been "not more than a few handfuls" per house, he said, although other material around the asbestos was also contaminated.

While ceilings had been fairly clear, asbestos had gathered around the edges of roofs, migrated down wall cavities and into the subfloors. No houses had been "riddled throughout".

Mr Poels welcomed the presence of Worksafe at demolitions because "not only are they watching what we do, they do keep our guys focused on the things that they should be watching too", and it gave the public "a level of comfort that it's not just letting people run their own show".

Shaw and Manteena have done the demolitions to date, but the government has now appointed eight other contractors as well, six from Canberra and Queanbeyan, three from NSW and one from Queensland. They began this week.

Asbestos Taskforce head Andrew Kefford would not release the cost of demolitions because companies were still tendering, but said it was "coming down" from the estimate of $160,000 per house.

Demolitions were on track, with 200 scheduled for 2016, and 300 for each of the two following years.

The program had its biggest day on Monday, when four homes were demolished – the Kaleen house, 4 Glasgow Street in Hughes, 6 Emery Place in Chapman, and one of the two farm properties, "Nerreman", at 350 Brindabella Road in Coree. A second face had been opened at the Belconnen tip for the homes, which averaged 300 tonnes of material each.

To date, no fibres had been detected during demolitions, with air monitoring equipment generally mounted on each of the four boundary fences and in the cab of the demolition crane.

Mr Kefford said the first 50 houses to be demolished had been spread around the city to give the taskforce benchmark values for re-sale in suburbs where clear blocks of land were rare, and for bushfire reasons. "A handful" of valuations had been done to date, but Mr Kefford would not release them, nor say how much higher they were than the amount paid to owners based on values at October last year.

He confirmed one valuation had been 40 per cent above the unimproved value set last year.

Two blocks had been offered back to the original owners and both had accepted the price, including one in a heritage area, he said.

But the bulk of land sales would not begin until the zoning change to allow unit titling of blocks passes the Assembly in February.

To date, 963 owners had agreed to sell, with 780 homes now in government hands, and at cost so far of $695.4 million.

Sixteen owners had refused to take part in the scheme and 20 others were still considering the offer, with most of those having until the end of December to decide.

With a focus on western-edge suburbs at risk from bushfires, most Chapman demolitions would be finished by Christmas, with Rivett, Holt, Kambah and Macgregor to follow.