He will now concentrate on his other property developer Bayfordbury Estates.
Fairview was a favourite to buy Rialto, as Barham has had a working relationship with Fairview stretching back 45 years. Most recently they have worked together on a mixed-use development at Gypsy Corner in west London.
A chairman for Rialto has yet to be appointed but managing director Stephen Casey will stay.
Rialto built 504 units in 2002; it had a turnover of £102m. Pre-tax profit was £21m, giving a pre-tax margin of 21%.