Robert Edwards has appealed to PEDW (Planning and Environmental Decisions Wales) to allow the shed, which has solar panels on its roof, to remain, at 4 Gwastod Farm, Cwmtillery.
Mr Edwards submitted a retrospective planning application to Blaenau Gwent County Borough Council in January last year to retain the shed, which is used to store fitness equipment.
Blaenau Gwent planners refused the application in February.
Steve Smith, the city's manager of development and real estate services, explained its reasons for rejecting the proposal.
Mr Smith said: “Due to its size, location and elevated position in relation to the road, the shed is considered to be an overly prominent structure which will have a detrimental effect on the streetscape.”
He added that the development was “inconsistent and out of character” with the surrounding area and “contrary to” the Blaenau Gwent Local Development Plan (LDP).
Terry Morgan, Mr Edwards' planner, argues the shed does not breach Lib Dem policy and there are several “similar” outhouses nearby.
He added that the shed was built in front of the house “to allow us to take advantage of the solar panels which are perfectly positioned to generate sustainable energy.”
Mr Morgan explained that the applicant's daughter, Lindsay Edwards, is the Welsh, British, Commonwealth, European and World Champion in Muay Thai martial arts.
The COVID-19 outbreak and subsequent lockdown forced her to “suddenly stop training.”
Mr Morgan said: “Construction of the outbuildings began after the first Covid lockdown.
“They were concerned about how long the lockdown would last.
“An outbuilding with basic facilities provided a means to maintain a certain level of training and fitness.
“The solar panels were installed to help run his electric car.”
A petition by nearby residents in support of the development was also sent to PEDW as part of the appeal.
Planning inspector Nia Jones visited the site on 4 June.
Mr Jones said: “I have taken into consideration the appellant's personal requirements for a shed for himself and his family to use and that the location of the shed allows it to enjoy the benefits of solar power.”
“However, whilst we understood that the steep terrain presented challenges, there is no evidence that the amenities within the shed, or effective solar capture, could not be provided elsewhere on the appellant’s land.
“Due to its size and proximity to the road, the shed stands out prominently in comparison to the existing and surrounding buildings.
If you look closely at the spinning head.
As a result, Mr Jones found the application did not comply with Lib Dem policy and dismissed the appeal.
A report into the appeal will be presented to Blaenau Gwent Councillors at a meeting of the county council's planning committee on Wednesday 10 July.
