Braathen Dendrokronologiska Undersökningar
Lunnevägen 2, SE-46144 Trollhättan, Sweden
The detached tower at Gammelgarn is situated less than 10 m SW of the church. All the walls are intact, and the tower is covered by a barrel vault pointing east-west. The squared base measures 9.3x9.3 m and covers an area of about 87 sq. m. The walls have at the base a thickness of about 2.25 m. About 50 cm above the level of the second floor is an inner recess of about 30 cm. That recess has not been used for carrying wall-head beams. The floor joists from the second up to the fifth floor have been tucked into the walls, all in east-west direction, which means that they have not served as anchor tie beams in order to balance the thrust from the vault. That means that the builder relied completely on the fact that the dimensions chosen for the walls would be more than sufficient to carry the vault.
In the northern part of the west wall is a door-way leading to the first floor. The wall surrounding the door-way shows on the inside traces of missing stones as if the wall had been broken through and the door-way were opened after the erection of the building. A round arched door-way in the east wall leads to the second floor. According to E. Bohrn (ATA 31/8 1937) part of the surface in one of north-eastern corner stones is the same as the stop face of a door frame, and the protruding piece of a slab is the remain of a cover over a door-way leading to a passage up to the door-way in the east wall.
Fire has burnt away all the floor joists except for two joists at the level of the fifth storey. In three beam holes in the walls stumps of joists have been found. They were burnt in one end. One of them has a curved corner which has been interpreted as part of the curvature of the trunk. One of the stumps in the east wall was easy to pull out. On its upper surface were corns of gravel, not burnt pieces of leaves and burnt pieces of plants. Among the pieces of coal were some coal grains with a groove along its side. It was perceived as carbonized corn. Because the ladder was standing on very uneven ground the stump was dropped and the grains disappeared. The grains indicate that the tower contained corn when the tower was attacked by fire. It is unknown in what century the fire occurred.
A stump of a burnt beam in the west wall has a curved surface at one corner. This was perceived as the curvature of the trunk. The outermost annual ring is dated 1202.