horizontal wall crack

[mwt]

Please Help,
This is my first post and advice is needed. We've had a large timber-frame dormer bungalow built approx 11.5m x 11.5m. Stick built 140mm timber frame with 600mm centres and a rendered concrete block outer skin.
this was built approx 1 year ago, and yesterday a horizontal crack appeared down the side of the wall, all 11.5m of it. This crack is only hairline, and approximately 1.5m from floor level. Up until yesterday no walls anywhere on the property showed any signs of cracks. It literally happened overnight. This has us a little worried to say the least! Any advice would be greatly appreiciated on likely causes and potential solutions. Please check out images of house. Thanks.

 

[noseall]

Is this elevation south facing?

 

[mwt]

The elevation is east facing, and doesn't get the sunshine. It has block paving surrounding the building. Approximately 8ft away is a dividing boundary wall. The foundations are a poured concrete type on dense clay. When the trenches were inspected by an engineer before they were poured,it was apparently very standard stuff, with no issues or special considerations. The area also has no issues with foundation movement.
thanks for your response.

 

[Pigeon85]

Interior/exterior or both?

 

[mwt]

Sorry if not clear, the crack is only on the outside exterior east facing wall. The building isn't finished yet and has only recently been plaster boarded. even though the timber frame is obviously designed to take the weight of slate and plasterboard insulation etc, do you think that over the last 6 weeks, the 220 sheets of plasterboard and its associated weight (220 x 60lb, plus insulation and otherbits roughly 15000lb) might have caused it??? However theoretically no real weight/pressure should be directly on the outer walls??