Collins has had just over a year in the role, which he took up following stints as deputy director of external affairs at the Home Builders Federation and chief of staff to housing minister Grant Shapps.
He is to leave CCHQ following the party’s conference next week to take up the job of head of communications Southern region for Barratt Developments PLC.
Mascall will arrive on 20 October with just seven months to go before the General Election.
He has worked at CCHQ before, in the role of health and education political press adviser between November 2010 and September 2012, going on to his current role as a spad to Patrick McLoughlin.
His earlier career including spells with Bell Pottinger, MSL Worldwide and Financial Dynamics.
Giles Kenningham, director of communications for the Tory Party, said: "Tim's departure is a big loss but in Ben we've got a first-class operator who will be a great asset to the press office."
At Barratt Collins will report to Gary Ennis, Southern region MD, with a dotted line to the PLC's head of public relations Paul Howlett and director of corporate affairs Patrick Law.