Bronze Age roundhouse at Flag Fen
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Bronze Age Round-House
Under Construction at Flag Fen
Click on image to enlarge!
© Photo by John Byford
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The
Bronze Age roundhouse at Flag fen is based on one excavated
at Fengate in 1976. Like many other Bronze Age Houses, the
Fengate example features an internal ring of roof-support
posts which would have been required to prop-up a heavy turfed
roof. Turf roofs tend to absorb (rather than shed) water;
and when waterlogged they can be very heavy indeed.
The internal
posts support a ring-beam comprising split timbers of ash
and oak. The posts themselves are mainly of oak: Timbers of
the ring-beam are joined to the post by loose mortice and
tenon location joints (similar joints frequently occur in
the Flag Fen excavation)
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The main roof rafters are 20 - 30 year old coppiced ash poles
which are fixed to the wall posts by square, split oak pegs
or 'tree nails'. The smaller purlins in the roof are of hazel.
The bed of the turf roof is formed from Norfolk reed donated
by Wicken Fen.
The outer turf covering was laid in two layers, the lower
layer was laid 'greenside down', the second 'greenside up';
the two sets of roots then combined to form a tightly knitted
turf. Over the years the turf has acquired a covering of drought-
resistant, mainly annual grasses which were not present when
the turf was first cut.
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The walls are formed around stout posts at the foot of each roof rafter and are composed of tightly woven hazel wattles, smeared with a mixture of clay, straw and dung, known as 'daub'. Wide external eaves help to keep the walls dry. |
Iron Age roundhouse at Flag Fen |
Iron
Age Roundhouse at Flag Fen built by volunteers
Click on image to enlarge!
© Photo by John Byford
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The Iron Age roundhouse at Flag Fen is
based on excavated examples from later Iron age settlements
at Fengate, and elsewhere in Britain. Houses of this general
type would have been in use around 250 BC.
The diameter of
the walls is 10 metres, which is typical of many known roundhouses
in the region. Most of the excavated examples had doorways
which faced towards the east and there was no evidence for
internal roof support posts; if lightweight partition walls
existed
(as they may well have done) there was no archaeological
evidence for them. |
Experimental reconstruction's have shown that thatched conical
roofs do not require internal supports, provided that a correct
roof-angle of 45° is maintained. This angle also allows
rainwater to be shed quickly and efficiently. Smoke from a
central hearth or fireplace was allowed to filter out through
the roof, as the strong draft from a chimney at the roof apex
proved experimentally very difficult to control. Firewood
produces less smoke when burnt dry and some woods, such as
willow, are naturally almost smokeless when burnt without
bark.
The Flag Fen Iron Age roundhouse was first built in 1988 and
suffered much from the effects of wind. It seems probable
that prehistoric versions were placed in less exposed places
among the alder trees that are often found on the edges of
fens and they would also have been surrounded by hedges, shrubs
and other buildings.
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