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Notes concerning the demolishing of the western end of a ten-year-old Stone age row house

Date: 
Tuesday, 22 May, 2012 to Monday, 28 May, 2012
Responsible: 
Kierikki Stone Age Centre
Number of Participants / Visitors / Audience: 
300

Introduction. Building of the Kierikki´s Stone Age Village was started 1997. It was based on new information found from excavations at the area and elsowhere in Finland. Village is situated by the river Ii, in the middle of two neolithic excavation areas. Following summer a double house was build. 2001-2002 a 3 room row house reconstruction was build. House in this publication is one part of that row house. Latest houses made from 2008 at the Stone Age Village are reed roof houses. Reed as compared to peat and birch bark appears to be much more water repellent. Kierikki main building is situated 500 meters from reconstructions. See the map of Stone Age Village

Notes concerning the demolishing of the western end of a ten-year-old Stone age row house. Roof materials are pinewood, plates of birch bark, and a layer of turf (10-20cm) on top.
Turf on the northern side was moist and rich in flora. Even some young birches from age 1-5 years seemed to like to grow on the roof. The southern side was obviously much drier. Still at least the lower part of the turf held moisture well, and it also had young trees and moss growing on it.
Birch bark plates (app. 60x70cm) right below the turf were in excellent condition. Only some of the plates from the lower part of the roof showed signs of some sort of mold or fungus on the surface. That did not have any effect on their function nevertheless.
The roof beams were also in moderately good condition. Most of the wood had softened and rot from its lower part (app. 10-30cm) (Fig 1).

Fig 1.
The volume of decay was strongest near the corners of the structure. Roof beams near or on top of the hearth were covered with soot, which had protected them from the effects of fungi or other sort of decay.
The topmost (fourth) tier of logs was in poor shape. One log from the southern side had already year 2011 broken near the south-west corner (Fig 2).

Fig 2 & 3.
Also the log in the northern side was heavily bent (Fig 3). The poor condition of these logs was mainly caused by the continuous presence of moisture, which practically never had change to dry properly.
The south-east corner of the log structure was inhabited by carpenter ants. The other corners also had lesser ant species or other beetles and critters living in them.
The lower tiers of logs had also rotted more or less. The second layer from the top was in moderate condition. Wood was mainly healthy and hard (only the corners had softened), but had become blue-stained all the way till depth (radius) of 5cm. (This bluing has no effect on the strength of the wood.) In general the southern side was in better condition due to the drying effect of sunshine (and perhaps the wind from the Ii-river).
The ridge beam was healthy excluding the parts right on top of the two center poles. The moisture had stayed in the joint and made the log soften till depth of 5 cm. (Fig 4.)

Fig 4.
Two center poles and other four smaller ones were in excellent condition and showed no signs of decay what so ever. All the poles had been charred before they were erected in 2002.
The floor made of modern planks (2x5 inch) was also in poor condition. The planks laid about 20-30cm from the ground, but the air beneath the floor could not change or move. This had led to severe decay of the planks, which in their horrible condition even formed a threat to visitors.
Main reason for the moisture in the structures can naturally be found in the Finnish climate. Dealing with long winter and spring time, together with great amount of snow can be challenging. In order to dry the structures (and keep them that way) after the winter, we should keep fire burning inside in much greater volume (and longer periods) than it has been possible so far.
Other reasons for moisture can be found in some mistakes made in the construction itself. The smoke holes or small openings right on top of the hearth seemed to have no effect on how the smoke could hover outside. The “structural” holes on the both ends of the house did the task well enough already. So, the openings did not let the smoke outside, but they let the rain in. Also, about two years after the house was originally built, according to the maintenance plan, the roof would have needed some improving. When the turf had settled and found its place, the top ends of the roof beams should have been cut. After that, new birch bark plates should have been placed on top of the ridge beam along with rolls of turf. These actions would have prevented turf from sliding down and revealing about 5-10 cm wide unprotected sector on both sides of the ridge beam.
The condition of the topmost tier of logs would have been greatly improved by constructing even a small eaves on the side, from where water would have had a chance to drip down to the ground and not stay in the structure. Another minor improvement would have been i.e. double the amount of birch bark in the lowest parts of the roof.

Images

Fig1
fig2
Fig3