Renovation work is now taking place on Church Cottage in Tutshill, close to the banks of the River Severn.
The author lived there between the ages of nine and 18 and in 2011 bought the cottage through a property company in her married name.
She paid about £400,000 for the house, which is said to have inspired key elements of the young wizard's story.
Land Registry records show in September 2011, Edinburgh-based Caernarfon Lettings Ltd, which lists the author's husband Neil Murray as a director, bought Church Cottage.
The property was sold by BBC producer Julian Mercer, who himself had bought it off the Rowling family in 1995.
At the time of the 2011 sale, the cottage was said to have elements of the Harry Potter story within its walls, including a cupboard under the stairs similar to the one where the Dursley family made Harry live.
The author also left her mark on Church Cottage with "Joanne Rowling slept here circa 1982" scrawled on one wall.
In 2019 Caernarfon Lettings Ltd successfully applied for planning permission to carry out renovations at the property, on Coleford Road.
In her teenage years JK Rowling attended nearby Wyedean School in Sedbury, where her mother Anne worked.
Her father worked at the Rolls Royce factory a few miles to the south on the outskirts of Bristol.
Harry Potter characters such as Professor Snape and Ron Weasley are said to be based on teachers and friends from Wyedean, where the library is named after Ms Rowling.
A quidditch team called The Tutshill Tornadoes, first mentioned in Harry Potter and the Order of the Phoenix, is also assumed to be based on the village.