crack where extension meets existing building

[Map796]

Hi

I have an extension that was built around 1983. There is a vertical crack on both the internal and external walls. It was skimmed a couple of years ago inside and the outside crack filled but it has reappeared - only a couple of mm. Is this normal movement or something to be concerned about?
Many thanks

 

[Map796]

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[Map796]

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[jeds]

Hard to say for sure but probably just a case of the extension foundation not being properly matched with the main house, which would cause them to move at slightly different rates. Nowt you can really do about it though. Maybe introduce a movement joint so it moves where you want it to.