The rental watchdog is trying to close the loophole which allows landlords evict tenants for renovations.
Some have been accused of using the repairs to bring in new tenants at higher rates in attempts to get around the rules of rent pressure zones.
Rent can't be increased by more than 4 percent a year in the zones, but the price can go up if there are new tenants.
Now the Residential Tenancies Board have released new guidelines which outline when a landlord can evict a tenant to work on the house.
"What we're trying to say is it's not really about an upgrade of the bathroom in a property," says RTB director Rosalind Carroll.
"It's more 'has the property been extended? Did you add a bedroom'?"