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Splice the mainbrace

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TECHNICAL & PRACTICE: Repairs to Lower Brockhampton's hall and gatehouse address years of decay, while preserving their integrity and charm

The Brockhampton Estate in the West Midlands is one of the most picturesque properties owned and administered by the National Trust.

At its heart stands Lower Brockhampton, a fine early 15th century cruck hall with spere truss, built within a wet moat by John Domulton, a descendant of the de Brockhamptons. To the south of the house, originally straddling the moat and erected circa 1600, is the gatehouse, its western wall standing on the dam which closed the end of the moat in the 19th century.

Both buildings were restored by J C Buckler in the mid 19th century.

That programme of work was particularly notable, as Buckler appears to have dismantled the hall range, to remove an inserted floor and other later modifications, and re-erected it in a fairly accurate, archaeologicallyinformed restoration, alongside the cross-wing which had survived in more or less original configuration.

He omitted to reconstruct the eastern truss of the hall against the cross-wing however, and so the wind-braces in this eastern bay have a peculiarly truncated and hunched appearance. He also renewed all of the infill-panels with brick-on-edge in the hall's south-wall frame.

His repair of the gatehouse was much less dramatic, but attempted to address the fundamental structural inadequacy of the little building, by providing corbel brackets beneath the jettied eastern floor-joists to resist the gradual capsize that was developing. All infill-panels and some timber frame members were renewed.

Picturesque decay The buildings were given to the National Trust in 1946, in poor condition. A major repair scheme was undertaken during the 1950s, resulting in the reconstruction of the south-wall frame of the hall using second-hand oak with nailed joints and brick infill-panels. The south wall of the cross-wing was repaired with machine-sawn timber and there was a similar reconstruction of the upper south-wall frame of the gatehouse.

Most of the 19th century lath and plaster infill-panels were retained;

those that were damaged or removed for timber repairs were replaced.

In 1991, Stainburn Taylor carried out inspections of both buildings and the adjacent ruined chapel, and reported that the hall was in danger of collapse of the south-wall frame, and that the south cross-wing was in serious disrepair. Works to the gatehouse, it was decided, could be deferred for seven to 10 years, despite its increasing instability.

During 1995-96, with grant aid from English Heritage, the owners undertook a major and successful timber-frame repair to the house.

The conservation and repair philosophy, which was to be maintained for repairs to both the house and gatehouse, was heavily influenced by the importance of the 'picturesque' restoration by Buckler.

Thus it was that the hall's southwall frame and cross-wing southwall frame were reconstructed to their 19th century configuration, using reclaimed oak for most repairs and new timber only for structural necessities.All were jointed throughout and given new wattle or split laths and daub panels, to decrease weight and to eliminate the water entraining characteristics of the brick panels.

Because of its configuration and construction, the gatehouse has always been a fragile structure.

The building is orientated northsouth over the moat, with a two-bay, close-studded, symmetrical timber frame at first-floor level, jettied on all four sides over the two-bay asymmetric ground-floor frame, with its heavy oak door carried from the central truss. Stability is dependent on the continuity of the bressummers, and the rigidity of the first-floor frame.

Lack of support At Lower Brockhampton, however, the original carpenters had installed a steep staircase cutting through the first-floor joists and one spine beam, with scant regard for the structural integrity of the east side of the floor frame. Consequently, the load from the east-wall frame and, especially the centre-truss storey post, caused the jettied joists to 'droop' over the wall frame beneath, and the bressummer to deflect substantially at its centre.

Compounding this distortion, the sill beam of the east-wall frame, spanning the moat also deflected, and the entire structure began to capsize to the east, probably quite soon after its completion. The deformation was progressive, causing the floor joists and beams to crush and break at their bearings on the frame beneath, so that the upper storey moved further and further out of alignment.

Over time, rainwater from the unguttered west roof-slope discharged directly onto the top of the west bressummer, with its close stud mortices uppermost. Inevitably, the east bressummer broke and the west became seriously decayed, a fate shared by the south bressummer - most exposed to the prevailing wind and without protection at all.

Originally, Buckler had arrested the movement temporarily by nailing oak corbel brackets to the east-wall frame to carry the floor joist-ends, and by installing a pair of braces from the moat walls to support the eastern cill beam. The patch-repairs of the 1950s certainly delayed the decay process for many years, but by 1998 stability had been further compromised by splitting of the post-head jowls of the central truss, and repairs were set in hand for 2000. Even though it was deemed necessary to replace only three pieces of timber in order to ensure the longterm stability of the building, these were the massive east, west and south bressummers. Because of their size - more than 3m in length and 450mm square - the use of reclaimed timber was both impractical and undesirable. It was decided that only the east and south bressummers would be replaced. The western beam would be repaired.

Further to this, the floor joists and beams would be retained in situ and strengthened individually with stainless steel flitches, and the tendency for the floor-frame to lift at its centre was overcome by introducing of a tie-rod between sill and spine beams.

To achieve this, it was proposed that the entire upper frame, without its stone-tile roof covering, should be lifted bodily from the rest of the building while repairs were carried out, and then lowered back into place onto the new and repaired timbers.

Beam me up Atotal of 20 hydraulic car-jacks were used as supports beneath the wallplates and tie-beams and were sufficient to raise the superstructure 300mm from the bressummers, after all of the pegs had been removed and the joints eased. In addition, a cofferdam was set into the moat to allow the section beneath the gatehouse to be drained, but kept wet to avoid shrinkage of the puddle clay. A temporary footbridge was placed over the moat to provide access to the house for visitors and a grandstand for inspection of the works in progress. It proved to be an irresistible attraction.

Clearly, such a procedure is not without difficulty or the risk of structural damage to the retained and lifted elements. There was concern that the repairs would necessitate a considerable amount of realignment of the capsize, in order to ensure stability of the timber frame. To avoid unacceptably high asymmetric loads on its joints and centre-truss posts, it was agreed to limit the correction of the picturesque tilt to the east by forming the east bressummer with a downward curve throughout its length, and the use of slip tenons to joint the already slightly shortened wallstuds to it.

Although the capsize has been redeemed by 100mm, the altered appearance of the gatehouse has been disguised by this ingenious and carefully-made sleight of hand. But to protect the repaired west bressummer from roof-water, a discreet gutter has been provided to the west roof-slope. After the works were completed, to the casual observer it looked as if nothing had changed!

Ian Stainburn is a partner in Stainburn Taylor Architects in Ledbury, Herefordshire. Tel 01531 634848

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