Now that so many able architects and enterprising bodies are seriously
taking up pise-building, the improvement in plant and technique should
be both rapid and considerable. The School of Pise Building established
at Hornchurch in Essex, by the Imperial Ex-service Association, should
alone provide us with much new and valuable knowledge of a highly
practical kind.
It is there, for instance, that various types of shuttering and rammers
are being experimentally tested side by side, and their relative
efficiency under varying conditions ascertained. Under some conditions
it is probable that the floor and roof timbers (destined for use in the
house under construction) will be found the most economical and
satisfactory form of temporary "shuttering" for the making of the earth
walls.
The pise "Test-House," built by Messrs. Alban Richards at their Ashstead
works, was built in this way, and proved highly satisfactory.
Another effective and more generally applicable form of shuttering
(designed and manufactured by the same firm) is illustrated in the
diagram reproduced below. It should be observed that wedges intervene
between the movable shutters and the uprights.
The method of employment of the "Mark V" shuttering is well illustrated
by the bird's-eye view showing the Newlands cottage under construction.
[Headnote: Alternative Shutterings]
In this matter of shuttering there is still, however, great scope for
improvement, and it may be hoped that soon ingenuity and experience will
jointly produce a complete pise plant perfectly fulfilling all the many
conditions enumerated earlier in the book.
Shuttering made by riveting plain galvanised sheet iron to one side of a
corrugated sheet has the qualities of lightness, smoothness, cheapness,
and rigidity, and the claims of the inventor and patentee are now being
put to the test in actual building.
[Illustration: PATENT SHUTTERING FOR PISE DE TERRE
_By W. Alban Richards and Co._]
There now seems little doubt but that pise blocks will be largely used
for partitions and chimney stacks where the soil is good enough, and
experiments are being made with a view to discovering the best and
cheapest way of making earth slabs similar to those of coke-breeze and
concrete.
The size aimed at is 18 in. by 18 in. by 3 in., the edges to be tongued
and grooved.
Certain "concrete" machines seem to lend themselves to adaptation for
the making of earth blocks, but it is necessary to remember that sharp
blows are required rather than a steady pressure, and also that we are
working with a _dry_ material. The ordinary primitive way of making pise
blocks is indicated below.
The hand-rammers are undoubtedly worth study and careful design. A set
of three seems to meet all ordinary requirements, and those shown on p.
101 may be taken as typical. They should be of hard-wood, smoothly
finished, and provided with long handles. They should be 9 in. to 12 in.
long, and about 5 in. by 4 in. at maximum cross section.
In the sketch they are shown "narrow-ways-on." No. 1 is used for
preliminary pounding and final finishing, No. 2 for general
consolidating, and No. 3 for working along the edges, against window
stops, and under cross-ties.
A South African correspondent, Major Baylay, makes interesting comment
as regards rammers and local pise practice:
[Headnote: South Africa]
"My experience of all black labour is, that they won't put any 'guts'
into it. They therefore want fairly heavy rammers, which they can lift
and drop, say a foot, and which will do the rest for them. The heat of
the sun and extreme dryness of atmosphere out here make it advisable to
cover up completed courses at once with sacking, moist for choice,
otherwise it is liable to dry out too quickly and crack. It dries out
uncovered at night very well, when there is no rain.
"The red loams of South Africa, where not too sandy, make excellent
pise. They or their equivalent are found almost everywhere. In the dry
state they set so hard that moisture added just before ramming is
useless. A large heap must be made, well damped and covered over with
moist sacking, and left until the moisture is distributed throughout the
mass. When about four or five days old, in ordinary weather, the earth
is ready to use--viz., just wet enough to bind when gripped in the hand.
It should be passed through a sieve. I use a sort of 'chicken run,'
8 ft. long, and throw the earth on to it before using. Six feet of it is
1/2-in. mesh, and 2 ft. 1/4-in. mesh; the reason for this is that, if
the earth is a little too dry, it does not always bind well with the
previous layer. Therefore, put a few petrol tins of the fine earth into
the shuttering first in order to ensure good bond, and throw the coarser
stuff in after."
[Illustration: PISE HAND RAMMERS]
_Second Note by Major Baylay, Peter Maritzburg, Natal, South Africa_
"I have completed a small building, and though weather conditions have
been as bad as possible, it is sound and very satisfactory.
"In my opinion, pise-building should not be attempted in the rainy
season in Africa. Earth contains too much moisture, and the power of the
sun dries it out too quickly and causes cracks.
"_Re_ plastering. I covered the outside and inside with a mixture of 6
earth, 2 sand, 1 blue (Hyd.) lime, the earth being the red, rather 'fat'
earth found everywhere, and the same stuff the house is built of. It is
put on thin with a trowel, after damping the wall. When it dries and
cracks, rub all over with a sacking pad covered with the plaster
mixture, but wetted to a thin cream consistency. It may sound an odd
method, but the natives do this work well, and the result is as good as
one can wish for. You can put tar or any wash (No. 6) on this."
[Headnote: Soils]