Built 25-years-ago, the revamp will be paid for by a long-term loan ensuring transfer fees are not affected by the costly project.
Concourses and supporters' amenities will be improved along with the Directors' Box being transferred to the East Stand. New corporate hospitality space and dugouts will be accompanied by the increase in dressing rooms for both the home and away teams and enlargement of the players' lounge. Media facilities will also be developed, including a new gantry for broadcast media.
The project will see the Hawthorns' capacity reduced temporarily to 27,000 with only corporate guests relocated in the Baggies last three games of the season.
"This refurbishment will vastly improve the match-day experience for all supporters and also provide the playing staff with much-enhanced facilities," Chairman Jeremy Peace said.
"The refurbishment will reduce the capacity by about 700 seats.
"Our average attendances in the Premier League were between 25,000 and 26,000 and roughly 22,000 in the Championship this season.
"Given those figures it is the right thing to do because everyone who comes to The Hawthorns will benefit from the improvements.
"We still have the option to extend the stadium's capacity in the future should the demand be there."