The Christchurch District Health Board says it will ensure people are kept in the loop as the hospital become's a long term construction zone.

The first stage of a $650 million revamp will start today, beginning with the construction of a new acute services building.

It will house around 400 new beds, an expanded intensive care unit, a helipad, and a brand new radiology department.

CEO David Meates says they'll be doing everything they can to keep disruption to a minimum while the four year project is completed.

"Over the next few years it is going to be a very complex building zone, and what we will be doing is making sure communications are really clear about where people can park, the access to the hospital and facilities."