Chalk, as a source of lime, has always been of high importance to
builders, and, until improved transport brought alien materials into its
old preserves, chalk was in general use for walling in the form of
roughly squared blocks.
Chalk again forms the basis of a compost that, used in the form of a
stiff paste, has been largely employed for building from the earliest
times down to the present.
"Pise de Craie," or chalk consolidated by ramming within a casing, is a
form of building that has been long held in high repute in France and
elsewhere, but which has only recently been given a serious trial in
England.
Chalk in all these forms, if fairly dealt with and reasonably protected
from the weather, is a most amenable and satisfactory material to build
with.
The last-named method particularly seems to promise results that should
satisfy the most exacting critics of the unconventional, as it assuredly
does those who inhabit the cottages so constructed.
The several systems of chalk construction are fully dealt with in the
pages that follow.
_Chalk Compost: Historical._--At the Ancient British village on West
Down, Chilbolton, some five miles south of Andover, delving
archaeologists have brought to light undeniable fragments of chalk
"Daub," with the wattle marks still clearly showing upon them.
This discovery is chiefly of academic interest, though it is a pretty
refutation to those who regard any building material save brick and
stone as "new-fangled," and it should also serve to hearten the doubters
and the timid amongst us who seek historic sanction for any departure
from current building practice.
_Composition and Uses._--In the Andover district Chalk Compost or "Chalk
Mud," as it is called locally, is prepared and used as follows:
The chalk is dug out in the autumn, and the frost allowed to play on it
during the winter. In the spring building starts, and the weathered
chalk is spread all around the outside of the walls. Straw is sprinkled
on it and it is then well trodden, usually by the workers, but sometimes
by horses. Sometimes chopped straw is added, sometimes unchopped straw
is sprinkled on. The quality of the walls depends very largely on the
preparation--that is, in getting the mud to the right consistency--and
the old hands know by experience when it is ready.
The compost is lifted on the wall by a fork and another man stands on
the wall and treads it in. It is then chopped down straight with a
spade. Some of the naked walls at Andover show traces of the courses,
which are usually something under 2 ft. in height.
Where a course has to be left unfinished it should be ended with a
diagonal ramp so as to splice in with the work that follows.
Some of the old builders seem to have been somewhat catholic in their
conceptions as to what constituted "chalk," and vague patches of earth,
loose flints and other stray substances not infrequently mar their work
and sometimes seriously reduce its strength.
As a general rule, the finer the chalk the stronger and more durable is
the walling.
What is aimed at is a conglomerate of small chalk knobs cemented
together by a matrix of plastic chalk and straw, the whole forming as
dense a mass as possible.
Grinding in a mortar-mill would probably reduce all the chalk to an
amorphous powder, which would not be desirable, and in any case such
mechanical mixing is quite unnecessary.
Building by ramming the moist compost between timber shutterings does
not appear to have been practised in the past, though there is nothing
against the method except its tendency to delay the drying out.
The drying of each course takes several days, depending on the weather.
A course is usually laid right round the building. It must be covered up
at night in case of rain, and when it is hard another course is laid on,
and so on till completion. The aim is to build during the summer and
autumn, and when the moisture has dried out, to render the exterior.
Where brickwork is used with chalk compost it is generally bonded in in
the ordinary way, but block-bonding the depth of a chalk course is a
better way of doing it.
The exterior corners of chalk buildings are the vulnerable points, and
these should therefore be well rounded off.
_Timber._--In the old work nothing seems to have been done to prevent
woodwork built in to the compost from decaying, though in many cases it
has survived surprisingly. In any new work, however, proper ventilated
air-spaces should be contrived or the timber ends treated with some
preservative.
The door and window frames are fixed to fairly large pieces of wood
built in across the thickness of wall, and other woodwork is fixed to
wood blocks built in in a similar way.
Picture-rails should be provided in all rooms, as chalk walls are apt to
flake and chip if nails are driven into them.
Lintels are usually of wood, and when plastering is carried down over
these some form of key must of course be provided to hold it.
[Headnote: Winter Work Barred]
_Frost._--New work must not be exposed to frost or there will be danger
of collapse, and winter work is barred out for this reason.
_Repairs._--Chalk compost walls are not easily repaired in that
material, and bricks are generally used, well bonded in.
_Chimneys._--Chimneys, too, are usually of brick, though there would
seem no reason against the flues being carried up in chalk, especially
if clay pipe linings were used.
The chimney-stacks above the roof might well be built in flint, the
corners being rounded off in deference to the peculiarities of the
material.
_External Rendering._--It is of the first importance that a good
weather-tight skin be maintained, and many old buildings have suffered
through neglect of this precaution.
The rendering was often of the poorest quality, more mud than lime, and
the constant repairs that the indifferent materials necessitated has
resulted in many of the old cottages becoming patchworks of variegated
plaster blotches, when not whitewashed over, which give an impression of
dilapidation by no means warranted by the facts.
_Rendering._--Given a good skin, however, of cement or cement and lime,
a chalk conglomerate wall will last indefinitely. So vital is the skin
that it is as well to put it on in two good coats--rounding off all the
corners and finishing it either with slap-dash or rough from the wooden
float.
Also, to ensure its proper adhesion throughout, wire-netting may be used
as reinforcement--being secured to the face of the chalk wall by means
of cross netting or wires laid on the wall as the building rises.
If the netting be of a fine mesh it also serves as an absolute barrier
to vermin, though pounded glass incorporated in the base of the wall is
equally effective.
_Strength._--Provided the wall has dried out thoroughly, any of the
ordinary loads occurring in a two-storied house can be borne with ease.
Chalk conglomerate walling, however, has no great lateral strength, and
it should not be asked to stand up to thrusts.
The roof, therefore, must be well tied, and should sit on the building
merely as a lid.
[Illustration:
+Details of Chalk Construction at Amesbury.+
(From a sketch by W. R. Jaggard, F.R.I.B.A., the copyright of
the Department of Scientific and Industrial Research.)]
[Illustration:
+Chalk Construction at Amesbury, Wilts.+
(From a sketch by W. R. Jaggard, F.R.I.B.A., the copyright of
the Department of Scientific and Industrial Research.)]
_Roof._--Though thatch is the traditional roofing material of chalk
cottages, any other will serve that is permanent and good of its kind.
The only special demand that chalk walls make is that the eaves shall be
generously overhung for their better protection from the weather.
Where, in later years, the boldly projecting thatch has been
thoughtlessly replaced by a slate roof with meagre eaves, or with none
at all, the walls have suffered accordingly.
[Headnote: Garden Walls]
_Garden Walls._--A chalk garden wall must be afforded just as much
protection as the wall of a house and on both sides.
The hat with which it is provided is of the highest importance to the
health and longevity of the walling.
Examples of garden wall copings are given in the sketches shown below.
[Illustration: WALL COPINGS.]
_House Walls._--Chalk conglomerate walls rarely exceed 18 in. in
thickness, and are usually the same upstairs as down.
A plinth of the same thickness as the chalk wall it supports is usually
carried up 6 in. to 18 in. above the ground level in rubble-work, flint,
or brick, being known as the "Underpin Course." Any of the stock
damp-courses are suitable, but they must be well and truly laid, as damp
feet are nearly as deleterious to a chalk wall as a leaky or inadequate
hat.
No special tools are required for this method of building, an ordinary
farm fork for lifting and a spade for the final chopping down of the
wall faces being all that are necessary.
A house built during the summer is usually fit for occupation the same
autumn.
_Old Examples._--Those who may wish to see buildings in chalk
conglomerate, both old and new, would do well to visit some such typical
chalk district as that lying about Andover in Wiltshire.
It should, however, be constantly borne in mind that most of the old
cottages were somewhat unscientifically erected by their original
jack-of-all-trades occupiers, that damp-courses and Portland cement were
unknown, and that the advantages of proper ventilation and the causes of
dry-rot were discoveries yet to be made.
Secondly, a large number of these cottages have been sadly neglected
either recently or in the past, and they bear the disfiguring marks of
their ill-treatment upon them now.
But a chalk cottage that is well found in the beginning, and that is
reasonably well cared for subsequently, has nothing to fear from
comparison with cottages built in the most approved manner of the more
fashionable materials.
Mr. James Thorold gives the following particulars of a block of three
chalk cottages recently built for Sir George Cooper on his estate at
Hursley, near Winchester:
"The chalk walling was done by Messrs. A. Annett and Son, of Winterslow,
near Salisbury, where this method of building has been kept alive from
olden days. It consists of working up the soft upper strata of the chalk
by putting a bed of it 4 ft. 6 in. thick on the ground, watering and
treading it to a sticky consistency with the feet, working in shortish
straw at the same time. When thoroughly mixed by the builder's mate, he
lifts up a forkful to the builder working on the wall immediately above
him, the latter catches the chalk, dumps it down on the top of the wall,
building an 18 in. course all round. As soon as the weather has dried
this sufficiently he goes round with a sharp spade squaring up both
sides of the wall. As this work is greatly dependent on the weather it
is well if the men have other work to fall back on, and that building
operations should be commenced in the spring or early summer. The wall
is built 18 in. thick to the first floor joists and 14 in. above. Chalk
in itself being very absorbent of moisture, the usual plan is to render
the outside of the wall with a lime mortar, which, however, requires
renewal every few years. To obviate this we fixed with long staples
1-1/4 in. mesh wire-netting over the outside surface of the wall to give
a reinforcement for a rendering of hair mortar and cement gauged in
proportion of 1 to 2 respectively, and left rough from the trowel. This
rendering was done at a cost of 3s. 3-1/2d. per square yard, which is a
substantial addition to the cost of the walling, but so far there is no
sign of a crack or hollow place behind it, and the cottages have kept
very dry. The walls were finished off with a limewash containing Russian
tallow and copperas.[9]
[Footnote 9: See recipes for Whitewash in Appendix (I).]
[Headnote: Cost of Three Cottages]
"As regards the cost of this block of three cottages, the result is
obscured by the fact that tall chimney-stacks with ornamental bricks and
appropriate foundations were built and reinforced leaded lights were
used in the windows to keep the building in character with the other
cottages on the estate, but at the time we estimated that the chalk
walling saved a sum of L54 as against the amount we should have had to
have spent in carrying out the building with bricks made on the estate,
and this had to include lodging money and profit, the builders being
independent men. The ornamental chimney-stacks were put in for the sake
of appearance, flues built up in the chalk being entirely satisfactory
and fireproof. The foundations are either flint or brick with a slate
damp-course.
"I consider that for a chalk country this method of building has many
advantages.
"(1) It saves cartage.
"(2) It can be carried out by a skilled labourer who can be
otherwise employed during unsuitable weather.
"(3) No fuel is required as in burning bricks.
"(4) If a suitable rendering is employed to keep it weatherproof,
and a good damp-course on the foundations, the cottages are nice
and dry and keep an equable temperature, chalk being a good
non-conductor.
"Sir George wonders if any method could be devised by chemical means to
harden the chalk and make it weatherproof; if this could be done it
might save the expense of the cement rendering."