Week 9 Lab Data Group D: Mortuary House Roof

Jacob Forster Rothbart // Group D

Concise version: North side of roof consists of 7 sets of purlins and 4 overlapping courses of hay thatch, not including the thatch over the ridge line. Thatch layer was ~6 inches thick.

Mildly verbose version: In this lab, Group D constructed the northern side of the mortuary house’s roof. First we collected our materials. We used precut (baled) hay for thatch, but we cut our own wood for wattling from the Carleton Arboretum. The area we were assigned to harvest from did not have many willow trees, so this wood was mostly ash, with a few other unidentified species mixed in. For our purposes, there was no clear difference when using the different species. The wattlewood we cut ranged from ~3/4 to double thumb thickness and five to eight feet long.

We used this wood to construct purlins, which add structural integrity to the roof and provide something for the thatch material to sit on. Each purlin consists of a pair of branches woven in opposite over-under pattern through the rafters that were added in last week’s lab. They were woven in such that each side had one thick end and one thin end. The thin ends were twisted into a withy and wrapped around the two wattle pieces. Occasionally a piece snapped while being twisted into a withy. When this happened we would add a third, shorter and thinner piece into the purlin. In total, our side of the roof contained seven purlins.

On top of this we placed our hay thatch, in overlapping rows. Each row of thatch was held down with a spar overtop, twisted into a withy on one end and tucked under the end rafter. Where additionalThe thatch on our side of the roof was approximately six inches thick.