Curved walls

Whatever the shape of curve, regular or complex there is no doubt that curved rammed earth walls have a very nice character. In many ways the transformation from the curved mould to the finished wall is a greater surprise than when building a straight line. Perhaps this is because we don't read the straight line for what it is, immediately transferring the visual image into a language of masonry we know. Brick and blocks make straight lines easily so rammed earth more easily equates to that.

Once a curve is revealed the nature of its production, that it clearly isn't brick or block, is immediately evident. So how was it made?, there the mystery and interest of something unique becomes clear, but not necessarily any immediate answers.

Curved walls in rammed earth are all about formwork. Sometimes that means bespoke panels, sometimes adjustable concrete formwork and sometimes just placing the walls so they looked curved.

In fact making curved rammed earth walls is exactly the same as building straight walls, the soil mix, the delivery and ramming, it is only the skill in formwork that is different. But in that formwork the nature of rammed earth as a cast or moulded material becomes clearer. And yet because we are not used to walls being made in this way, being loose soil transformed to solid wall with no intermediate process and because of the

necessary scale of a wall its curving nature catches the attention.

Because a curve is always moving, not stopping at orthogonal junctions, but shifting towards or away from the eye, convex or concave, it has a mystery especially to people used to the straight line. Stepping into a traditional circular building, a wigwam or African kitchen can be a disorientating experience without the regular stopping points for the eye, for the mind. The curve just keeps moving.

So rammed earth curves give the opportunity to express this shift in perception and the opportunity to experience form in a different way.

Because formwork has two sides there is no necessity to have the two sides of the mould the same, one side may be curved while the other side is facetted. This can be useful where a curve expressed on the inside is transformed to a series of outward facets, either for a decorative architectural effect or more functionally to attach insulation or rain-screen.

Additionally the geometry of curves is very stable producing useful effects with lateral loads. Curved walls used for retaining structures can resist a lot of overturning without themselves being very thick. This effect, effectively a flat arch was used to good effect with rammed chalk at Pines Calyx.

The cost of rammed earth curves is often highly competitive. Formwork may be more or less expensive but once assembled the filling is the same as for a straight wall. But curved walls in brick and block command a much higher cost, making rammed earth a good cost comparison. Much depends on the competence of the carpenter.