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THE PFETTENDACH

The Sparrendach works with only one kind of rafter; the
Pfettendach differs from it in employing two kinds—one
of light, the other of heavy, scantling. The heavy, or
principal, rafters rise from the ends of the tie beams to the
ridge of the roof, forming powerful trusses that carry
purlins and, as a rule, a ridge piece; and it is upon these
longitudinal timbers (purlins and ridge piece) that the
lighter common rafters of the roof are mounted. In the
Pfettendach the major burden of the roof is transmitted
by the purlins to the principal trusses which discharge it
upon the walls at the beginning and at the end of each bay,
to points which, if the walls are built in masonry, are usually
reinforced by buttresses.

The best known variant of the Pfettendach is the roof of
the Early Christian basilica[208] and all its Mediterranean
medieval derivatives. But the Pfettendach is also, as we
have seen, the standard roof in the North Germanic
territories of Sweden, Denmark, Norway, and Iceland.[209]

The two earliest surviving examples of a vernacular
medieval Pfettendach are the roofs of the barn of the abbey
grange of Great Coxwell in Berkshire, a dependency of the
Cistercian Abbey of Beaulieu in Hampshire (figs. 349-354)
and the barn of the abbey grange of Parçay-Meslay, near
Tours, in France, a dependency of the monastery of Marmoutier
(figs. 352-355). The former dates from the first
decade of the fourteenth century;[210] the latter belongs to a
group of buildings that tradition ascribes to Abbot Hugue
de Rochecorbon (1211-27).[211]

The barn of Great Coxwell (figs. 349-351) is 152 feet
long and 44 feet wide (external measurements not counting
buttresses) and reaches a height of 48 feet at the ridge. Its
vast roof rests on purlins which are held in place by
seven principal trusses sustained by posts, and six intermediate
trusses in cruck construction rising directly from
the aisle walls. The uprights of the principal trusses rest on
tall bases of stone almost seven feet high, and are framed
together 30 feet above the floor of the barn, first crosswise
by means of tie beams, then lengthwise by means of
arcade plates—a reversal of the normal and more common
procedure of housing the plates beneath the tie beams in
a recess cut into the head of the supporting posts (fig. 357).
The tall, narrow proportions of these trusses are exciting.

[ILLUSTRATION]

354.A PARÇAY-MESLAY, NEAR TOURS (INDRE-ET-LOIRE), FRANCE

BARN OF ABBEY GRANGE, 1211-1227. PLAN

The twelve roof-supporting trusses of the barn are not in alignment with the buttresses of the two long walls. This could be interpreted to mean
that the present frame of timber is not the original one, if this conclusion were not invalidated by the even more startling observation that the
buttresses of the two long walls fail to align with one another. An oral tradition, the precise sources of which we have not been able to identify,
claims that the original roof of the barn was destroyed by a fire in 1437 during the war with the English. Radiocarbon measurements taken of
samples extracted from two different posts did not confirm this tradition (see Horn, 1970, 28; and Berger, 1970, 111-112).

It is possible that the craftsman who built the masonry shell of the structure did not know what the carpenter had in mind; and even the
carpenter, in many cases might not have known of what number of trusses his roof-supporting frame of timber would be composed until he was
apprised of the length and strength of the available timbers. In its ultimate form the roof was composed of twelve trusses dividing the space
internally into thirteen bays each of a depth of 13 feet. The location of the buttresses would have suggested a barn of seven bays, each of a depth
of 24 feet, which is possible but structurally more risky.

[ILLUSTRATION]

354.B PARÇAY-MESLAY, NEAR TOURS (INDRE-ET-LOIRE), FRANCE

BARN OF ABBEY GRANGE, 1211-1227. TRANSVERSE SECTION

This is, to the best of our knowledge, the only surviving five-aisled medieval barn of transalpine Europe. There were others. The plan of the
abbey of Clairvaux and its grange of Ultra Alba (a short distance away on the opposite bank of the river Aube) records, besides two five-aisled
structures of this type, two barns that even had seven aisles. The largest among these was 210 feet long and 120 feet wide; 40 feet longer and
wider than Parçay-Meslay (for a plan and bird's-eye view see Horn and Born, 1968, Pl. XIX, figs. 10 and 11).

Since most Cistercian monasteries possessed between ten and fifteen outlying granges, the number of buildings of this kind must have been legion.
Clairvaux and Morimond counted twelve; the Abbey of Foigny fourteen; the Abbey of Fontmorigny seven; and the Abbey of Chaalis, fifteen.
On many granges, as in Ultra Alba, there were not one but two or even more such structures. Since at the beginning of the 13th century there
existed in France some 500 Cistercian monasteries, the total number of barns of this order only, and in France only, must have ranged
between 5,000 and 10,000.

[ILLUSTRATION]

355. PARÇAY-MESLAY, NEAR TOURS (INDRE-ET-LOIRE), FRANCE

BARN OF ABBEY GRANGE, 1211-1227. INTERIOR LOOKING UP INTO THE ROOF RIDGE

The roof of the barn is made stable by means of a sub ridge running parallel to and below the main ridge beam. The two are stiffened by
St. Andrew's crosses (two bracing struts half-lapped at midpoint at right angles and tenoned into the paired ridge beams). This remarkable
engineering came to be adopted in and widely diffused by 19th-century steel construction some 600 years after this huge timber frame was made.

The building is made structurally stable by means of its extraordinary system of internal bracing, and is without need of an external source of
support such as might have otherwise been provided by massive masonry walls. In consequence of its self-contained equilibrium, supplied by the
genius of a master carpenter, the building provides the evidence that demonstrates the handsome masonry walls were constructed after completion
of the wooden frame.

A feature of striking beauty is the three-way double braces
which rise from the main posts to their connecting long
and cross beams. By reducing the unsupported length of
the beams that they brace to less than one third of their
total length, they prevent them from sagging under the
weight of the superincumbent rafters, while at the same
time protecting the frame from rocking and swerving. The
walls are built in roughly coursed rubble with buttresses of
high quality ashlar masonry. The two large doors in the
gable walls are modern. In the Middle Ages the barn was
entered broadside through two transeptal porches, one of
which had on its upper level the office of the supervising
monastic granger.

The barn of Parçay-Meslay (figs. 352-355) is quite
as impressive. It lacks the breathtaking steepness of
Great Coxwell, but its space is of a vastness that can only
be compared to that of an Early Christian basilica or of a
modern airplane hangar. It has a clear inner length of 170
feet, and a clear inner width of 80 feet. From floor to
ridge it measures 44 feet. Its vast tile-covered roof is
supported by twelve aisled trusses which divide the space
lengthwise into a nave and four aisles. The barn of ParçayMeslay
is the only example of this type to have survived
the French Revolution; but the existence of other barns
of similar design and even larger dimensions, dating from
the twelfth century, is attested by Dom Milley's engravings
of the Abbey of Clairvaux, published in 1708.[212] It is a
purlin roof like Great Coxwell, and similar in many other
respects, but the trusses of Parçay-Meslay are more closely
spaced and are all of the same design. The assemblage of
arcade plate and post follows the more common pattern of
housing the plates in the head of the posts and locking the
tie beams into both of these members simultaneously from
above by means of dovetail joints and mortice-and-tenon
joints. The bracing struts are short and sturdy, and the
posts throughout have joweled heads.

As in Great Coxwell the purlins ride on the back of
principal rafters that run parallel to the common rafters,
a short distance farther inward (figs. 353-354). As in Great
Coxwell these inner rafters are braced by diagonal struts
that rise from the top of the tie beam. In Great Coxwell
the principal rafters over the nave terminated in the ends of
a collar beam that stiffened the corresponding pair of outer
rafters some distance below the ridge of the roof (fig. 350).
In Parçay-Meslay they are buttressed against a king post
that reaches all the way up to the ridge of the roof (fig. 354).

There are other differences. Unlike Great Coxwell, Parçay-Meslay
has no gable trusses. Instead, all longitudinal
members (plates and purlins) terminate in sockets built
into the masonry walls. A more important difference, however,
is that while in Great Coxwell a major portion of the
roof load is transmitted to the masonry of the long walls,
in Parçay-Meslay it is almost entirely absorbed in the
timber frame. The walls, of course, contribute their share
in steadying the work, but there is a complete set of outer
posts addorsed to the walls on either side of the barn, making
the timber frame virtually autonomous. In Great Coxwell
the buttresses of the masonry walls are in careful alignment
with the timber frame. In Parçay-Meslay carpenter and
mason went separate ways. No single buttress is in line
with any of the timber trusses.

One of the most remarkable features of the carpentry of
Parçay-Meslay is the measure taken, both in the lower and
upper stage of the trusses, to restrain the frame from moving
longitudinally. In the lower stage this is accomplished by
straining beams running parallel to the arcade plates, some
12 feet beneath them. They are tenoned into the posts just
below the springing of the main braces and are braced in
turn by short angle struts (fig. 353). In the upper stage of
the trusses the same task is performed by the introduction
of a sub-ridge running parallel to the main ridge, some 9
feet beneath it, and stiffened in its relation to the main
ridge by means of St. Andrew crosses (fig. 355)—a notable
piece of engineering.

The roof of Parçay-Meslay is a typical Continental purlin
roof, of a kind that is well attested through many other
Continental barns of the thirteenth century.[213] This type
was still in use in the fifteenth, sixteenth, and seventeenth
centuries as the standard form for the roof of market halls.[214]

[ILLUSTRATION]

The grange lies 9 km. northeast of Tours and ca. 1 km. north of the village of ParçayMeslay.
Marmoutier, its mother house, lay on the outshirts of Tours and slightly
upstream, on the Loire's north bank; nationalized in 1818, the abbey was then razed.
The grange at Parçay-Meslay stands as a solitary reminder of the former grandeur of
this abbey, once among the most powerful houses of Christendom.

[ILLUSTRATION]

GREAT COXWELL, BERKSHIRE, ENGLAND

357.B

357.A

BARN, ABBEY GRANGE, FIRST DECADE 14TH CENTURY

DETAIL: ASSEMBLED, DISASSEMBLED, principal post, tie beam, roof plate

[ILLUSTRATION]

CHICHESTER, SUSSEX, ENGLAND

356.B

356.A

ST. MARY'S HOSPITAL, END OF THE 13TH CENTURY

DETAIL: ASSEMBLED, DISASSEMBLED, principal post, tie beam, roof plate

At St. Mary's, the roof or arcade plates are set into a shoulder of the principal
posts. A projecting tenon of the latter is mortised into the tie beam which in
this manner comes to rest above the roofplate. All converging members of the
frame are so carefully interlocked by protruding and receding elements so as to
prevent any slipping, shift, or dislocation.

In the joinery of the Barn of Great Coxwell the tie beams are likewise mortised
into a tenon of the principal posts, but the roof plates are notched over the tie
beam—an assembly which, because of its relative rarity in England is there
referred to as "reversed assembly". The latter is rather common on the
Continent. Both methods are fine examples of medieval carpentry.