Boarding-houses, which critics say can be overcrowded, unsafe and unsanitary, do not have to be licencsd or have a permit.
They are instead covered by various laws and rules.
The council's environmental health manager, Mervyn Chetty, says it mostly has only anecdotal evidence about boarding houses.
"Maybe the existing legislation is adequate to deal with boarding houses - we just need to have a look at it."
If there were gaps in the regulations, the council would have to decide whether that needed to be addressed by by-laws or some other mechanism.
Mr Chetty said 20 boarding houses would be investigated.
Shutting down premises would be a last resort if problems were found.