The building, which was abandoned in the 1970s, has been decaying since then.
Cargill’s Castle Trust chairman Steven De Graaf said making a start on the stabilising was a huge relief.
"It has worried me for the last couple of years, because you can see signs of deterioration.
"It’s been a struggle to raise enough money to get to this point; it’s really nice to get that support now."
Through various grants, donations and fundraisers, the trust had about $300,000 to get the stabilisation done.
But right now, securing some parts to slow the rate of decay was more important than waiting for the trust to raise all the funds needed, he said.
Work began earlier this week: contractors are drilling holes into walls and attaching steel frames to the top wall of the structure.
"We’re doing the tower on the front first just to get a feel for it, because this is something the contractors have not done before," Mr De Graaf said.
The first phase was expected to take two or three weeks, weather-dependent.
"Our aim is to have it at a stage where people can come and have a look around and learn a bit about its history."
It is estimated it will cost up to $2 million to get it to that point.
