The Insurance and Savings Ombudsman is advising flood-stricken east coast residents to contact their insurance company before cleaning up.

Around 50 homes in Gisborne and Wairoa were inundated with water on Monday after torrential rain saw up to 200 millimetres fall in 24 hours.

Ombudsman Karen Stevens said it's a very stressful time for those affected, but contacting insurance companies now will save problems later on.

"The biggest mistake is cleaning up the damage before they contact the insurer and then have no evidence of the items that they have lost or the items that they've thrown away that were damaged."

Stevens said people shouldn't delay getting insurance companies involved so that the damage can be assessed by the insurer.

"Ordinarily, people are asked to or expected to do it as soon as they can, so that it allows the insurer to send out a loss adjustor to investigate."