Hi I work for a property management company and we'd like to use images of the properties which we manage within our portfolio on our website and social media/marketing materials. They are just images of the building/block of flats or estate as a whole. Do we need to get permission from the owners to use these images?
This comes under "legal" not photography - the opinions of random internet strangers are just that - opinions with no legal backing.
Generally, around the world [you didn't say where you are] if you are taking pictures of a private property from a publicly accessible location - ie, from the street - you need no permission.
There are exceptions to this - airports, military bases etc etc. but generally if you take a picture from the street you can get away with it.
Note 'get away with it'; it's been known for people to actually test this in court, with no single conclusive result. Google Streets has photos of almost every property in the world... but not all.
If you take a picture from on the property itself, you do need permission.
As you are presumably in the business of selling/managing these properties for their current owners, would it not be simpler to include that permission in your standard contract they have to sign before you take on their business?
For the actual contract wording, you would have to consult your lawyer.
Caveat: If the properties are rentals, then different rules again will apply to indoor shots.
Late note: as mentioned in comments - title to the photograph itself rests with the photographer, not the property owner. Their permission is a completely separate entity - again, see a lawyer.