This paper is concerned with an experimental investigation into the phenomenon of plastierboard peaking, the unsightly undulations and cracks which develop in ceilingas as a result of moisture movement. It is shown that the peaking is caused by the differential expanison/contraction rates that occur under easonal moisture change of plasteboard and timber. The differential ovement is accommodated by a combination of sheet stressing and joint movement. Where the joints are formed by flexible joining tapes the accommodation is almost entirely wityin the joint with highe joint movements. Where more rigid joiints ae formed, for example with back blocking, more sheet stressing and less joint movement aries. The construction of joints with tapes on the underside only leads to high joint movement and the usightlyy rotations chanracteristics of peaking.
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