outdoor living » the 10 bushcraft books » huts & thatch (pt. 3)

.sewn ridge thatching

With very long material two heavy poles may be slung on slings, so that they lie on either side and hold the outside edges of the ridge thatch material down.

Another method of thatching a ridge is to tie on two battens to the top of the topmost layer of thatching. The ends of the ridge thatching material sewn to these two battens must overhang the sewing of the topmost layer.

An alternative method is to sew the ridge material on to three poles, one of which acts as a false ridge, and the other two, which are sewn tightly, hang over the ridge some 12" or 18" [30 or 45 cm] on either side of the centre pole. This ridge thatch material can be sewn on the ground in lengths of from 6' to 12' [1.8 to 3.6 m]., and when the roof is ready for ridging these are laid over the actual ridge proper and the two side poles allowed to hang on either side, covering tile top layer of stitching.

.crown ridge thatch

A third method of ridge thatch is to make a "crown" and overlap this over the ends of the top layer of thatching.

.guttering

Under some conditions it may be necessary to put a "valley" in the roof, and this will require guttering. Efficient guttering can be made from wide sheets of bark inverted so that they lie with the hollow side in the valley. An alternative is the use of hollowed-out palm trunks or the extra-wide leaves of the plicate palms can be laid to overlap each other. Considerable care must be taken with this guttering if you are to have a watertight roof.

.flashing

There are occasions when flashing may be required. For instance, there may be a tree growing through the roof where the ridge pole is held up, or for some reason some of the structural poles or tree trunks may project through the roof thatch. When flashing is required, simply spin up a length of thin rope from grass or other soft fibrous material (see Bushcraft "Ropemaking") and bind thatching round the tree or pole. Continue the binding an inch or two above top of the thatching material. Make sure that it is tight and secure. The rain will run down the tree trunk, come to the flashing binding and, seeping over it, come on to the thatch, from where it is led by natural flow to the thatch of the roofing.

.rammed earth

This method of building makes a permanent structure which is well insulated and low in cost. The only materials required for the walls are earth containing certain wide proportions of clay and sand or other gritty particles. The earth must also be free from organic materials such as grass, roots and the like.

Rammed earth buildings can either be built by erecting forms or by ramming earth in blocks (like large bricks) and laying these in courses.

Foundations and footings are made by setting large stones in clay in the foundation trench. Clay is in many ways better than concrete for rammed earth buildings, because it is impervious to moisture.

If concrete foundations are used, then it is necessary to put in a dampcourse, but with clay and stone no dampcourse is needed.

.foundations

The foundations (footings), as shown in the photograph, are large stones set in clay. The foundations extend from 6" to 9" [15 to 22.5 cm] above ground level. Foundation trench is 2' [60 cm] wide by 1' [30 cm] deep, and lined with at least 1" [2.5 cm] of clay. After laying the stones in the clay, they are rammed to make a firm bed.

The advantage of this method of laying foundations is that there is no cost, and the method is speedy.

One man can dig and lay 15' to 20' [4.5 to 6 m] of foundation in a day.

The foundation must extend above ground level so that in the event of very heavy rain the surface run-off will not reach to the rammed earth wall.

.soil qualities for rammed earth

Any "heavy" loamy soil is suitable for rammed earth building. The soil must be just right for its moisture content. To find out the light "consistency", roll up a ball of the earth (about the size of a golf ball) between the palms and drop it from a height of about 1' [30 cm]. If the ball breaks up, the soil is too dry, and moisture must be added before ramming.

If the ball does not bleak from 1' [30 cm] high drop, then hold the ball above the head and drop it again. If the ball does not shatter into small fragments with a 6' or 7' [1.8 or 2.1 m] drop, then the soil is too moist and must be allowed to dry out before ramming.

The qualities in the soil are easily determined. There should be not more than 70 per cent sand, and not less than 30 per cent. There should be not more than 70 per cent clay and silt, and not less than 30 per cent.

If Sand or Grit is between three-tenths and seven-tenths soil will be O.K.

To discover it the soil is all right for rammed earth work, take a glass tube ten inches long, or, alternatively, divide a glass tube into ten equal divisions. Dry some of the earth, crumble it to fine powder, and fill the tube. Take the exact quantity which was in the tube and put it into a billy or dish, and wash thoroughly in running water until all the clay and silt particles have been washed out. Dry the remainder and then put back into the tube. The level will tell you the approximate percentage of clayey content that was in the soil.

If the soil has too much clay it will crack; if too little clay or too much sand or organic matter it will crumble.

This photo shows a rammed earth Hostel in course of erection. This hostel is to provide snow accommodation for 20 people. It is 35' by 22' [6.6 m], 8' [2.4 m] walls, 1' [30 cm] thick. The total cost of the building is estimated to be under $300 [in the 1970's]. The only materials bought are iron for the roof, timber for roof, floor, doors and windows, and 5 bags of cement for facing of the rammed earth wall and also for a 3-inch top sill for same.

.forms

Forms can be made and bolted together, and in these earth can be rammed of, alternatively, moulds can be made and the earth rammed into these to form blocks, and these blocks are then laid in courses like large bricks.

If forms are used they need not be more than 2' or 3' [60 or 90 cm] high and 6' to 8' [1.8 to 2.4 m] long. The forms are held by bolts which, when tightened up, clamp the form to the wall.

When ramming, shovel in 3" or 4" [7.5 or 10 cm] of earth and ram until the earth "rings". This is quite a definite sound, unmistakable from the soft "thud thud" of the first ramming strokes.

Ramming is hard work, and tiring.

When the layer is "ringing", throughout its length, shovel in another 3" or 4" [7.5 or 10 cm] of soil, and repeat. Rammers should be from 6 to 8 lbs. [2.7 to 3.6 kg]. A hardwood base, about 4" x 4" x 10" [10 x 10 x 25 cm] long, handle maybe a 5' [1.5 m] length of gaspipe.

If moulds are used they must be of a design which can be quickly "knocked down" to remove the rammed earth block and as quickly re-assembled.

One man can fill and ram about 9 to 12 cubic feet [0.25 to 0.34 cubic meters] in a day.

Rammed earth walls should be at least 9" to 10" [22.5 to 25 cm] in thickness for an 8' [2.4 m] wall, or 12" to 15" [30 to 37.5 cm] if a top structure or greater height are required.

Rammed earth walls may be protected from driving rain either by providing a wide overhang to the eave, by plastering with a cement or lime mortar, or by giving a cement "skin" by brushing on a thick cement-sand mixture (one-to-two proportion). However, even without the cement skin, rammed earth will stand up to a hundred years or more of weather.

.log cabins

Where timber is plentiful and white ants (termites) not prevalent and a structure of permanence is required, the Log Cabin is suitable. It is permanent, solid, and easy to build. The construction is simple. Cut your logs (which should be of roughly uniform diameter) to within a few inches of the required lengths. Lay the bed logs, which should be the heaviest logs. See that, these are laid square. Where the end logs lie across the back and front logs, halve or scarf the sites for the log.

The remainder of the construction follows exactly the same method. The logs are carved into each other.

These are two methods of scarfing logs for building. The flat surface of the bottom log always "falls" outwards, so that when any rainwater blows in it will not find a place for easy lodgement, but will drain away because of the natural slope of the bottom of the scarf. Chinks between the logs should be filled with clay.