The couple bought 41 Corlette Street in 2015 as their home then purchased the neighbouring terrace at No.39 off market at the start of last year. The pair of terraces are believed to have been built in 1904.

"We completely gutted them," Mr Bowen, who is a construction supervisor for Montgomery Homes, said.

"We left the facade because of heritage listing but completely gutted them. There's not one bit of timber through the whole place that was pre-existing. So they are basically brand new terraces that are over 100 years old but modern throughout."

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They took each from being two bedrooms to four bedrooms and three bathrooms. Mr Bowen said they would keep No.41 but sell No.39.

The floor plan of each home was nearly doubled with a 10-metre extension at the rear and both now two storeys throughout.

They went for a versatile layout. Three bedrooms and two bathrooms are upstairs. Downstairs is a fourth bedroom/study or second living. Open plan kitchen, dining and living extends to a paved courtyard.

There are polished concrete floors downstairs and Blackbutt timber features throughout. Skylights allow for plenty of natural light and there are stone vanities in the bathrooms and stone benches in the kitchen.

"We pulled out that much sand when we excavated so we ended up doing an infill slab into the old section," Mr Bowen said.

"There's not many terraces around that have concrete floors in the older part, so when you open the door it's a bit different.

"We wanted to keep the outside looking completely heritage and inside we tried to keep [traditional elements] where we could. We went with a steel bath because that's what was in here. We tried to keep some things in the terrace way."

It is being marketed by PRDnationwide Newcastle and Lake Macquarie's Russell Dawson. It is open at 11am on Saturday. A price guide is yet to be set.