Denbighshire case studies demonstrate common problems and typical
Broster and Carol Thickins
House, Ruthin (above) following restoration and (below right) one
of the many repairs carried out to the timber frame.
and the surrounding counties are fortunate to have a large number
of surviving timber framed buildings. This good fortune is enhanced
by the wide variety of building types and styles and the variation
in methods of construction of the timber frame structures over
a long period of time.
panels are generally either of wattle and daub or, as at Nantclwyd
House, of oak staves and woven laths with a lime plaster or daub
finish. The wattle typically consists of oak staves with woven
hazel twigs, and the daub is likely to contain (in very variable
proportions) clay, lime and a mixture of cow dung and straw. Brick
is also common, but this is usually a later insertion after earlier
daub has failed or alterations have taken place, and is traditionally
set in a lime mortar. Of these, daub and lime plaster are most
likely to be original and are best suited to timber frame construction
because they absorb and release moisture relatively quickly. This
allows the frame to breathe and reduces the risk of moisture being
trapped against the timbers causing decay.
The most important
issues to be considered before embarking on the repair of infill
panels include, first, discerning whether the existing infill panels are
original or, if not, whether they have developed historic significance
in their own right. Second, it is also essential to consider
the condition of the panels and of the adjacent framing, and,
particularly in the case of the replacements, whether the framing
has been adversely affected by the type of panels used.
to these issues, and in the light of modern requirements for conserving
energy, decisions also need to be made on whether to improve the
thermal performance of the infill panels and, if so, how insulation
can be introduced without harming the historic fabric. These issues
are illustrated in commissions which Donald Insall Associates
has recently received to undertake repair and restoration projects
to two timber framed buildings in North Wales for Denbighshire
County Council; Nantclwyd House and the Tŷ Coch barn. Both projects
included repairs to infill panels, the reinstallation of missing
sections of framing, and the relocation of external doors to their
The two buildings
are about five miles apart and, according to dendrochronological
evidence, both were constructed in the early 15th century. This
area of the UK is rich in timber framed buildings of this period,
and similar dates have been returned from the analysis of a number
of other examples in the surrounding area. However, their
similarity ends there: the two buildings have very different functions
and forms of construction.
House is a Grade I listed building in Castle Street, in the centre
of the ancient market town of Ruthin. Occupancy of the house has
been traced back to 1435, but the change in its status came in
1490 when John de Grey, who held the Lordship of Ruthin, granted
it to John Holland. Since then the building has passed through
several owners in its life.(1)
part of the building comprises the substantial remains of a medieval
three-unit timber framed house with hall and flanking cross wings.
As is usual for buildings of such age, extensive alterations had
been carried out over the centuries. In this case it is thought
that the majority of these date from the second half of the 17th
century when Eubule Thelwall enlarged the house, bought Lord's
Garden at the rear, and constructed a large summer house in it.
However, it seems likely that the north-west range is an even
earlier addition than this. Most of the extensions are timber-framed
structures, except for the substantial west wing which is constructed
mainly in stonework.(2)
In the 18th
century, the Wynne family extended the parlour and remodelled many
of the rooms. The most recent private owner was Samuel Dyer Gough
who purchased the house in 1934 and undertook a great deal of
restoration work. It was his widow who finally sold the house
to the county council in 1984.
of traditional split oak lath and daub render panels at Nantclwyd
House: the upper storey awaits its daub finish
has seen a wide variety of uses. Originally a town house for wealthy
and influential owners, during the 19th century it was tenanted,
accommodating a girls' school between 1886 and 1893, and it subsequently
became the rectory for the neighbouring parish of Llanfwrog. Between
1834 and 1970 part of the house was also used as judges' lodgings.
of the Tŷ Coch barn is less well documented. The barn is in the
village of Llangynhafal to the north of Ruthin, and the Royal
Commission on the Ancient and Historical Monuments of Wales believes
that the building was originally constructed as a 'house and byre'
of, significantly, five bays (rather than the more usual four
bays) using six cruck-trusses, four of which remain. It
is thought that the timber box frame replaced the original outer
walling in the 18th century, and the trusses were adjusted then,
but not moved from their original locations. The building appears
to have remained in use as a typical agricultural structure since
then, although modified and adapted over the years.(3)
Associates' approach to restoring both buildings has been to combine
an understanding of the historical development of each building
with a detailed assessment of the condition of its fabric and
to use this to inform the extent and detail of the repairs. As
a result, the timber box frames and cruck trusses have been sensitively
repaired mainly in oak with the minimum of disturbance to the
existing fabric and the least possible removal of timber. In places,
some more modern repair techniques have been used to effect sound
construction joints, in order to avoid removing excessive amounts
of timber. Generally, these have involved stainless steel plates
and brackets fitted carefully and, wherever possible, in concealed
House retains two forms of panel infill: interwoven hazel wattle
and also split oak staves and laths, both being covered with traditional
daub. Following discussions with the conservation officer and
Cadw, it was agreed that the existing panels would be repaired
as necessary using similar materials to the existing, but where
new panels were required, such as where the frame had to be reinstated
or where inappropriate earlier repairs had been removed, these
would be infilled using split oak staves and split oak laths.
for repair of the panels were briefly considered by the design
team, including the use of stainless steel mesh and composite
insulation panels, but it was quickly agreed, following discussions
with Cadw, the conservation officer and the historical and interiors
consultant, that it would be most appropriate to reinstate the
panels using one of the original methods. The use of oak staves
and laths was preferred as oak lath has greater durability than
wattle. (Being all sapwood, hazel wattles are particularly prone
to beetle attack.)
infill panels were required, the oak staves were inserted into
the existing stave holes in the underside of the timber at the
top of a panel and then sprung into grooves in the timber below.
The panels gained considerable rigidity as the laths were woven
in and pushed down.
The daub or
lime plaster was then applied from both sides simultaneously so
that it bonded in the centre where the two materials met. The
panel was then finished with a lime plaster skim coat neatly scribed
into the edge of the timbers.
The mix for
the daub used was clay, chopped straw and lime. The use of cow
dung as an ingredient was not considered to be necessary and was
omitted. It was essential to keep the daub damp and well protected
during the curing period to prevent the daub shrinking excessively
and cracking occurring. This was achieved by using wet hessian.
of a traditional panel of this type are that:
- the thickness of the daub/plaster can be adjusted to cope
with variations in the shape and thickness of the framing
where less than perfect timbers have been used
- over the years, as timbers move or suffer degradation,
gaps around the edges of the daub and plaster panels can be
filled with a lime putty
- if hairline cracks in the plaster did appear, they could
be filled simply by the regular application of limewash, as
section of the cruck frame of Tŷ Coch Barn near Ruthin, prior
to restoration commencing
of the north elevation of the barn illustrating the poor condition
of the frame: part of one of the cruck blades is visible.
At the Tŷ
Coch barn, holes and grooves are clearly visible in the remaining
framing, but unfortunately none of the original infill remains.
Most of the panels had been infilled using bricks of a variety
of sizes, some of which appeared to be medieval, and may have
been the recycled remains of an earlier chimney stack or other
feature. They were almost certainly introduced at a much later
date, probably in the mid 19th century when the farm complex was
enlarged. The end walls of the barn were also reconstructed in
stone, probably at this time.
of the external timber box frame at Tŷ Coch was poor, particularly
at low level where layers of accumulated dung have accelerated
decay of the baseplate. It was therefore necessary to remove all
of the brick infill panels in order to repair the frame, with
the bricks being set aside for possible reuse. However, the use
of brickwork poses a number of problems:
- Traditionally, brick panels relied purely on friction to
hold the panels into the frame. They can therefore become
unstable if there is movement in the frame. (This can be mitigated
by the use of mesh reinforcing strips in some courses pinned
to the sides of the framing, but this is still less secure
than a woven panel.)
- There is also a tendency for the bricks to hold moisture
against the edges of the frame, leading to decay at these
points. This is made worse if the brickwork is either built
or repaired using a cement-based mortar.
- Bricks also add weight, which may become a critical factor
if timber sections are slender or have been subject to some
- If the framework has distorted (or includes irregular shaped
decorative panels) a considerable amount of cutting or packing
may be necessary. This is the case with the panels found at
is currently being undertaken before a final decision is made
on the type of infill to be used here, but it is likely to be
split oak and laths with traditional daub, which is more suitable
for the fairly slender timbers found in parts of the wall-framing.
to meet modern standards of insulation must inevitably be heavily
influenced by the proposed end use of the building, which differs
greatly in each of these two cases. The decision also needs to
take into account the internal appearance of the external walls
and the standard of comfort required.
House is to become a museum and visitor attraction, with each
room depicting a particular period during the life of the building.
Internal finishes are therefore now of painted daub with exposed
timber or restored and refitted timber panelling of the appropriate
period, with some rooms papered on lime plaster finish (where
oak laths have been used). Here the standard of comfort takes
a lower priority since the building will be minimally heated,
and most users will be passing through.
The Tŷ Coch
barn, on the other hand, will be let for office accommodation.
Although wattle and daub may have been a reasonable insulator
for its period, modern requirements are much greater, so here
the walls will be dry lined internally using a modern insulating
system which will be fixed independently from the timber framing.
This allows the external infill to be reinstated in a historically
appropriate method, and the modern insulation element is fully
reversible: that is to say that it could be removed without affecting
the historic fabric further. Windows and doors will also be introduced
into the panels as carefully and unobtrusively as possible without
disturbing the existing structure and leaving the frame 'expressed'.
have two very different timber framed buildings passing into the
next phase of use in their life, carefully adapted to ensure that
they can be used and enjoyed with the least possible impact on
their historic character.
reports have been used as sources of information on the history
of the buildings:
(1) CJ Williams,
Nantclwyd House, Ruthin, A History for Denbighshire County
(2) R Morris,
Nantclwyd House, Ruthin, An Outline Archaeological and Architectural
Assessment. Mercian Heritage Series No 172, 2002
(3) R Suggett,
report on Tŷ Coch in the National Monuments Record for
Wales, July 2006
This article is reproduced from The
Building Conservation Directory, 2006
BROSTER is a chartered building surveyor and Senior Associate
in charge of the Shrewsbury office of Donald Insall Associates.
He is accredited in building conservation with the RICS.
THICKINS is a chartered architect who works as a consultant
to Donald Insall Associates and is based in the practice's
Shrewsbury office. She has a particular interest in the
repair of timber framed buildings.
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