Stone Roofing in England Terry Hughes.
| THE WELSH
MARCHES AND BRISTOL |
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| Since
the earliest days of the history of the science of geology the Welsh Borderland
has attracted the attention of geologists by the great variety and interest
of its formations, for in no other area can the sequence of the Palaeozoic
rocks be seen to such advantage and in such a comparatively small district.
(Earp and Hains 1971, 1) |
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| Unlike other
stone slate regions of England, the Welsh Marches have not been defined by
their geology for this study. Geographically, the stone slate usage extends
from the Bristol Channel to Shropshire. For this study it is defined to the
west by the Welsh border, and to the east roughly by a line due north from
Gloucester. For convenience, the Pennant stone of the Bristol region has
been included with the Pennant of the Forest of Dean and South Wales. |
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| The region
cuts across the grain of the geological succession from the Ordovician to
the Jurassic; a period of about 300 million years. This makes for interesting
roofs but difficult research. Because the geology changes rapidly over short
distances, and because so many different stones have been used for roofing,
this section is inevitably incomplete. There is no doubt that many small
delves, hidden away in forests, in deep narrow valleys or on remote hill
tops, still remain to be discovered. Similarly, there are many sources of
stone slates from the same formations across the border in Wales. These have
not been included in this report but they should not be overlooked when searching
for potential new supplies. From Llandeilo in South Wales to Ludlow the lowest
part of the Silurian Pridoli Series consists of micaceous flaggy sandstones,
known as the Tilestone Formation. (Today it is more correctly the Long Quarry
Beds in the south and the Downton Castle Sandstone Formation in the north.)
Its use is differentiated by the initial capital in ‘tilestone’, otherwise
used to describe any stone slate. |
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| An example
of the difficulty in determining the historical provenance of stone slate
roofs in the region is provided by Ashleworth Tithe Barn, north of Gloucester,
which was to be re-roofed during 2001 (Figs 60 and 61). The barn is thought
to have been built between 1481 and 1515 but the roof was reslated in 1885
and again in the 1940s. In 1942, Harold Trew, a Gloucester architect, reported
that the roof was covered with ‘Cotswold stone tiles’ (unpublished letter
to the Society for the Protection of Ancient Buildings, 1942). In fact, the
roof today includes red and grey-green Old Red Sandstone and Forest Marble
slates but it is not possible to determine which is the earliest or even
if they were both installed at the same time. The Old Red Sandstone is only
six or seven miles away at Newent to the west or the same stone could have
been brought up the Severn from the Forest of Dean area. The Forest Marble
would have come overland from the Cotswold Hills fifteen miles to the east. |
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| To further
complicate matters Ashleworth actually stands on rocks of Jurassic-Lower Lias
age and field walls in the vicinity include thin stone which would be suitable,
and therefore might have been used in the past, for roofing (Fig 62). Stone
for field walls was never carried far. Indeed, stone walls often only exist
because they are a ‘waste product’ of a nearby quarry which was primarily
worked for more valuable products such as the Lias masonry of Ashleworth
barn. The convenience of a nearby supply of Lias roofing might well have
been the overriding factor in deciding what was used on the roof originally.
(Sources of lias stone are discussed below.) |
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| So, at present,
there is a mixture of stone slates and an indeterminate history of other stones
from an earlier date. In similar situations elsewhere, commentators have
added further confusion by incorrectly identifying sandstones as limestones
and vice versa, because they have incomplete knowledge of all the possible,
local options. |
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