An "incredible amount" of work is needed to make Portsmouth Football Club's stadium "fit for purpose into the new century", its CEO has said.
The redevelopment of Fratton Park's North Stand Lower began this month as part of a £11.5m upgrade of the ground.
Chief executive Andrew Cullen said the improvements would mean greater safety for fans, and better facilities for disabled supporters.
There will also be 600 additional seats. The current capacity is 19,700.
Plans include wider staircases, additional safety barriers, better levels and sightlines, and additional kiosks and female toilets.
It is expected to be completed in May, with work then moving on to Blocks F to K over the summer.
Mr Cullen told the BBC: "When supporters come to a football match the one thing that matters to them most is feeling safe, and when we've done some of these works it's shown a lot of problems, as you would find in any old building, that need to be put right."
He said longer term plans could mean extending the North Stand further, and using it to house conference and exhibition spaces.
He added: "We've already started producing plans... to take the capacity up to 24-25,000 minimum, possibly beyond, by extending on that footprint and then we'll protect the stadium going forward as we hope the club develops and progresses up the next levels."
About 1,200 supporters have been relocated during the redevelopment works, but Mr Cullen said everything would be done to give fans as close to the same position as they had before.
The redevelopment will be the first major change to Fratton Park since 1997.
In 2017, former Disney CEO Michael Eisner took over the club from the previous majority shareholders, the Pompey Supporters' Trust, and promised to significantly improve the facilities.