Crack in Paramount Board

[Beckmeister General]

My upstairs walls are all paramount boards (eggcrate inner with plasterboard either side). On the landing above one door, there is a permanent hairline crack above one corner of the door both sides. (I think this is a joint ). No matter how many times I score out both the cracks and fill in then sand down and paint the crack soon reappears. The door never gets closed so its not that its a slammed door that shakes the wall.
Has anyone got an idea or a filler product so the cracks doesn't reappear?

 

[noseall]

It is a common structural problem that arises with ANY openings with 90 degree corners, be them windows, doors or otherwise.

Airplanes even changed their window shape from square to round because of the problem.

 

[Richard C]

Gouge out the surface plaster around 30mm (60mm total) either side of the crack, take it down as far as the board if you can. Stick 2 overlapping layers of fibreglass reinforcing tape to fill the width of the gap & then stick another layer over the centre of that. PVA the lot, fill & blend in; if that don’t hold it, nothing will.

 

[Beckmeister General]

Thanks
Is this the standard stuff you can buy from B&Q?

 

[Richard C]

Thanks
Is this the standard stuff you can buy from B&Q?

Yes B&Q do it; glass fibre reinforcing tape

 

[Beckmeister General]

Many Thanks Richard