GENERAL ASPECTS OF CONSERVATION OF WOODEN CONSTRUCTIONS

Nowadays we usually use traditional tools and methods for conservation of wooden buildings in Finland. During this workshop no. 4 we try to make the participants familiar with traditional Finnish methods of log constructing. Our aim is to make all the work using hand tools and old techniques without machines. The whole process beginning with the production of materials and ending up to the restoration of a granary will be carried out with traditional way.

THE BUILDINGS IN FOCUS

We will have three sites to work with in Takkila. They are the old cowshed, moved to its present site to be used as a barn, the storage for clothes and the granary. All buildings are made of wood using a horizontal log construction.

5. OLD COWSHED

This building has originally been built in 1907 as a part of the courtyard next to the main buildings. It has been moved to its present site around 1924 and has been used as a barn for straw. There is a date 1919 in the wall. Lately the building has been used as storage.
The log frame rests on the piles of corner stones. There is no floor construction, only ground inside. The building should have a low foundation, because there is no floor construction and otherwise the door will be situated too high.
The notching method for log construction is made with extending log ends. The two uppermost layers of logs in the long walls project outwards a width of half a log.
There are many holes and openings in the walls, but the main entrance is in the long wall. The door still exists inside the building and there is even an upper part of the hinge left on the wall. There are also several marks showing that the log frame has been moved. The marks are contradictory in some walls so we might assume that the present log frame has been put up of two or more buildings or then they have used old logs for repair works.
Originally there has been a plank roof. Now there are shingles under the protecting tin roof.
Between this building and the next one there has been a shelter for hay and straw; the marks of the beams can be seen on the wall.

Conservation measures
Now the lowest sill logs are missing in all the walls and they should be returned. In the walls A and B the existing lowest logs have to be replaced. In the wall B also the existing logs 2 and 3 should be replaced. The door should be repaired and the lower part of a hinge must be reconstructed. Corner stones must be arranged anew, because the log frame is now set too high.

11. CLOTH STORAGE SHED

This building has probably been built in 1909. There is this date inside on the wall.
The use of the building has been for storing the clothes and also the maids have used is as a sleeping place in the summer time. Now it is used as an exhibition of its original use.
The construction is horizontal log construction with extended log ends and corner stones. The floor planks have been installed in between the two lowest logs, so the ends are visible outside. There is also a beam running under the floor in the middle of it.
The building has two stories and there is an unattached stair inside. The second floor is supported with beams running from wall to wall and the floorboards have been laid on top of them.
The building has a shingle roof covered with protecting tin roof.

Conservation measures

The whole building has sunk and the sill log of the wall D is under ground. All the sill logs have rotten and must be replaced as well as the log number 2 of the wall D. At the same time the whole building should be lifted up, so the sill logs are no longer in the ground.
All the floorboards are lying on the ground next to the wall D and they are rotten from that end. The floorboards should be cut on top of the floor beam and the rotten ends should be replaced with new boards.
The original boards have been made so that first the log have been hewn roughly to be square, then sawn into two and finally it has been hand planed from the sawn side to get the smooth surface. New boards should be made similar way.

17. GRANARY

The granary dates at least partly from 1824. This date can be found in the back wall of the building.
Originally the building has been used for storing the flour. Lately it has been empty.
Granary has been build using thin (80 - 100 mm) logs and no pegs. The notching has been made with extending log ends.
The logs have first been cut with a pit saw and as the walls have been ready they have been hewn with an axe. Boards from the surface of the logs have probably been used as a part of the roof construction. Wall D is almost collapsing and there are damages in the walls B and C too.
The foundation for the building is high so called "frog log"-construction. This high log construction stands on the corner stones.
The whole log frame has moved and is partly damaged because of the poor foundation.
The roofing is now made of metal, but the original material has been planks covered with birch bark and wooden poles on top of it.
The floor is made of cleaved boards. Some of them are rotten in the corner of the walls A and B.

Conservation measures

The whole building needs to be put straight. The damaged logs and floorboards should be replaced with new ones, made with similar techniques as the originals. The original roof construction can be restored.

MATERIAL PRODUCTION FOR TRADITIONAL FINNISH WOOD CONSTRUCTION

Birch bark

One of the most common materials for the roof has been birch bark. It is very durable and resistant against water. The birch bark roofing was constructed so that planks carried the sheets of bark and there were wooden poles on top of it to keep the bark on the roof. Also stones were used for the same purpose. The birch bark has also been used as an under layer for a tile roof or for shingles.

Birch bark is collected from living trees in summer. The bark comes loose easiest in June - beginning of July. When the bark is loosened a strip of bark is left to carry the nutrient for the tree so the tree does not die. The bark is collected as strips or as sheets and it is stored in bundles under a weight to make the bark straighten.

Shingles

Shingles became popular as a roofing material in the 1800s and especially after 1850. At first they were produced by cleaving the wood. The work began by cutting the log into about 60cm long pieces, which were then split into four parts of which the pith was cut away. Then the wood pieces were cleaved into shingles using a special knife. Cleaving was done either according to the radius or the tangent of a tree trunk.

After 1850's they started to use planes operated by horses or sometimes by men. Next step was to use machine planes. Also the industrial production of nails increased the popularity of a shingle roof. Nails were not so expensive any more. Planed shingles were about 5mm thick when cleaved ones were only about 3 mm.

It is said that the cleaved shingles lasted better even they were thinner than planed ones. This is because cleaving did not break the cell tissue as did the planing.
In the 20th century the sawn shingles became common, but they are not so durable as the cleaved or even the planed ones.

Cleaving the boards

Cleaving has several advantages over sawing, being that the grain of the tree, in other words the cell tissue is followed and not crossed. Crossing these transverse cells with the saw actually damages their structure, opening them up so that the structure of the wood is damaged at tissue level. Wood remains strongest when kept in the original shape in which it grew.

The pine chosen must be slow grown. Where a forest is thick it usually grows more slowly as each tree competes for the light and nutrition. Pines growing in sandy areas are usually the best choice as they don't grow too fast.

Once a tree has been felled, its crown cut off, and it has been de-barked and placed suitably, preparation for splitting can begin by ascertaining the twist and how the tree can be split so as to avoid the line of branches and their knots. The trunk should first be split in half - one can only expect to get two wide planks from each tree or then for more narrow ones.

The cleaving begins with making a cut in the end of a trunk then hammering the wooden wedges in gradually until the trunk splits. Then these halves are either split into two according to the radius or the tangent. If split according to the radius, then the final four planks are split in the direction of tangent, if split immediately along the tangent, then only two planks are gained.

Sawing the boards

Sawing is more recent way to produce planks and boards than cleaving. The process begins with hewing the two sides of a log straight. Then on the straight surfaces the lines are marked for the sawyers to follow.

This hewing and marking happens on the ground then the log is lifted up to the sawbuck. The sawing begins from the top of the log and ends up to the base.

The upper man stands either on the log itself or then on the side planks while the lower man stays under the log. The more skilful sawyer works up on the sawbuck and the younger or inexperienced one saws below. The upper man controls the saw so that it goes along the marked line while the man below makes the hard work of sawing. Some saws work both ways pushing and pulling so both men have to work, but traditionally it was the man below who really sawed.

When sawing approached the sawbuck the lower handle of the saw was unattached, the saw was pulled out and the log was moved so that the sawing could continue. Sometimes they used wedges to keep the sawing gap open, so the sawing was easier.

The final end of a log was sometimes just torn open. This was easier and quicker way than sawing until the end.

Tar production

The tar could be produced from many wood species but the best is pine, because it has the highest resin content. The idea is to split the wood material and produce tar, turpentine oil and some other chemicals by dry distillation.

At first the wood material is chopped into small pieces and then heated either in a tar pit in the earth or in a closed barrel-like retort. It depends on the burning process how much tar and what other chemicals are produced.

When the burning process is over, the tar is not ready for use yet. It needs to stay in a barrel for a year or so to let the "tar water" and some other components separate from the tar.

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