Protesters are steeling themselves for a legal battle with developers after being granted a stay of demolition on three historic St Heliers cottages.

The Environment Court issued an injunction this afternoon stopping the destruction of the three Spanish mission-style houses until at least January 24.

By the time it was issued at about 3pm, demolition crews had already destroyed half of one of the 1930s houses.

Audrey De Ryn, a campaigner to save the cottages, says a group of about 50 protesters wept tears of joy when the injunction order was granted.

"It is quite incredible. They had been crying beforehand, but there were tears of joy. People hugged each other. Someone described it as bittersweet."

They are now vowing to continue the battle to save the houses in the Environment Court, she said.

Save Our St Heliers Society spokesperson Dr Gabriel Reid is upset the partial demolition was carried out while the court was still deciding whether to grant the temporary injunction.

He served the court papers to developer Mike Markham of Anacona at 3:05pm yesterday and demolition crews arrived at the site this morning.

"He knew this matter was before the courts."

Auckland Council should not have allowed the demolition without a comprehensive heritage assessment of the houses, Dr Reid said.

"I am furious that we are served by a mayor and a council that are so inept that it falls to a group of citizens to remind them of their most basic duties."

On Monday, Auckland Mayor Len Brown said there was no affordable way to save the cottages from demolition.

He had sought a delay to the demolition after councillors turned down an attempt to place a heritage order on the buildings by a vote of 14-7 on December 16.

"Absolutely everything that could be reasonably and legally done was done in this case, but unfortunately that was not enough."

A letter to councillors from Council Chief Executive Doug McKay said there was no evidential basis to impose or seek heritage orders to protect the buildings.