The main contractor should acquire a Contract Works Policy that covers the full replacement value of the project. This will protect the project from hazards like fire and malicious damage. In addition to providing safety, the insurance will be needed for the bank to release any funds.
You should finalise arrangements for the required loan or mortgage with the bank before starting any construction work. This includes ensuring that the release of funds aligns with payment milestones set in the building contract and schedule.
Note that during the construction phase valuations may be required for the bank to release funds. This depends on the mortgage agreement and it is important the project budget allows for these.
Engaging legal advice to outline and review contracts will ensure clarity and the inclusion of all necessary information.