The original church from the 1100s and 13th century had a plan that was, as far we know, very unusual for stone churches from the Middle Ages found in Northern Norway. It had a rectangular nave with a narrow choir. Before the west end of the nave in the Alstahaug church was torn down, the church dating to the Middle Ages was measured. The nave measured 12.2 x 9.3 metres and the choir 6.3 x 6.2 metres, on the interior. The old choir has the most lavish decoration. On the exterior there is a pedestal that has an Attican base profile. A horizontal profiled band runs along the lower edge of the windows. While above and below the eaves, there is a small blank arch frieze, which rests upon an S-profiled moulding (ogee-shaped profile).