Work on the five bridge structures will start on Monday 9 June.
Welsh Government are responsible for maintaining the M4 in Wales rather than local councils.
It says the motorway will generally remain open with two out of the three running lanes operational in both directions for the duration of the works.
The Welsh Government say that when full closures are required, they will be limited to overnight only and will be well-signposted in advance. Temporary speed limits will also be implemented to ensure driver and worker safety.
To set up a contraflow system, the M4 will be closed overnight westbound between J37 Pyle and J39 Groes between 8pm on Monday 9 June and 6am on Tuesday 10 June.
There will be a further overnight closures in both directions between 8pm on Tuesday 10 June and 6am on Wednesday 11 June – and again overnight from 8pm on Wednesday 11 June to 6am on Thursday 12 June.
There will be an overnight closure for westbound traffic for 1 night on the M4 between J37 Pyle to J39 Groes from 8pm on Thursday 12 June until 6am Friday 13 June.
Then an overnight closure eastbound for 2 nights this time between J38 Margam to J37 Pyle from 8pm on Friday 13 June to 6am on Saturday 14 June – and again from 8pm on Saturday 14 June until 6am on Sunday 15 June.
Diverted traffic will be directed to use the A4229 and A48 through Pyle.
From Sunday 15 June until Wednesday 16 July there will be central reservation works, with traffic flow reduced from three lanes to two lanes in each direction. A 50mph speed limit will be in place during this time for safety.
Welsh Government Cabinet Secretary for Transport and North Wales, Ken Skates said: “Fixing and maintaining our roads and making them more resilient is a priority for us. I understand the works will cause disruption and I’d like to thank motorists for their patience whilst the work is taking place, however it is important it is carried out during periods of drier and warmer weather to ensure it can be done effectively.”
