The operator said the work was being carried as part of plans for the Elizabeth line, which runs from Abbey Wood, at its northeast, to the terminals as well as Reading, to have 4G coverage by the end of next spring.
The Elizabeth has become a vital link to Londoners and it now carries 600,000 passengers a day. Heading to Heathrow, it provides a faster alternative than using the Piccadilly line, which also serves the airport.
Howard Smith, the line’s director, said: “These works were planned several months in advance and should help ensure that the Elizabeth line infrastructure operates reliably.
“Network Rail and HS2 are also preparing for their new railway and station at Old Oak Common, which will also mean some future closures.
“I apologise for any impact on journeys over the weekend and would advise customers to check before they travel using TfL’s travel tools, and plan in advance as trains and rail-replacement buses may be busy.”
The action will take place on November 25 and 26.
Alternatives to Heathrow Express
Due to the work, there will be no Elizabeth line service running between Paddington and Abbey Wood, although a service between Liverpool Street and Shenfield will be available. Rail-replacement buses west of Ealing Broadway will be in operation.
Piccadilly line trains will serve Terminals 2, 3, and 4 at Heathrow but no trains will run to or from Terminal 5. There will also be no service between Acton Town and Uxbridge across the whole weekend.
Paddington rail station will also be closed on November 26 so customers travelling into London, from the west of England, will all need to change at Ealing Broadway for services into central London on the Central or District lines.
Central, Jubilee, and Piccadilly lines alongside replacement buses are expected to be busier due to the work.
Next month, there are set to be national rail strikes, although the Elizabeth line will not be impacted.