Manchester United would like to expand and improve Old Trafford, but doing so would leave the club temporarily "homeless".
The current capacity of Old Trafford is 74,994 and they'd like to expand it to 88,000.
"We haven't left the easiest stand until last," managing director Richard Arnold told United We Stand, quoted in the South China Morning Post. "The South Stand -- the Sir Bobby Charlton Stand -- is the last unexpanded stand.
"It's sandwiched in a fairly narrow strip of land between the pitch and the main Manchester to Liverpool railway. There's not much space on either side of the stand, meaning that it's a very complex engineering challenge to deliver.
"It would be a multi-season challenge and it isn't certain that there's a way of doing it which doesn't render us homeless. We have the biggest fanbase in the country and we're not in London, where we could use Wembley.
"So that's not a light challenge for us and we don't want to give up the home advantage that we have here. Moving elsewhere would be difficult and the logistical issues associated with expanding the South Stand are not negligible. And that's before you start getting into how big the expanded stadium should be."