We are a multi disciplinary practice with years of experience specifying appropriate repairs, assisting with renovations and conversions, and carrying out inspections of historic buildings and structures across the UK.
We work closely with other heritage professionals to ensure our engineering solutions are appropriate and sympathetic to the building or structure. Following the Society for the Protection of Ancient Buildings Approach, we are able to combine proven principles with practical techniques to conserve and restore historic buildings for the future.

We have a working relationship with local authorities, stakeholders, private homeowners, and have built up a working relationship over many years with larger clients including The National Trust. As well as being able to assist with the conservation of historic buildings, we are also able to provide a range of expertise for projects, including temporary works design, geotechnical support and drainage and pavement design.

We work on the following types of heritage assets:

  • Residential properties
  • Estates and country homes
  • Vernacular buildings
  • Agricultural buildings
  • Places of worship
  • Public buildings
  • Commercial heritage

Our services include:

  • Structural condition assessments of existing buildings – from undesignated, empty barns to Grade I listed buildings
  • Assessment of existing foundations
  • Structural advice on proposed alterations or conversion plans
  • Design of repairs and new interventions
  • Structural monitoring
  • Assistance with maintenance plans

Extensive surveys, renovation and refurbishment of Grade II listed Rudd Hall, East Appleton, N Yorks

Repairs to Wall End Barn, Langdale 

Tweddell and Slater Ltd worked in conjunction with Lewis Surveying Associates for the client, The National Trust, to design and implement repairs to a 17th century cruck frame barn in Langdale, within the Lake District National Park. 

There is evidence of the age of the barn in the form of a will from 1612, in which the farm owner provided for his godson to build a barn with three pairs of trees (or crucks). At some point in the 19th century, with apex of the crucks were removed and the pitch of the roof was reduced, possibly having changed from a thatch to a slate roof finish. The building was first listed in 1967 as Grade II and was re-roofed by the National Trust around 1985. 

Tweddell and Slater first completed a structural survey due to movement noted in the cruck frames, both laterally and longitudinally. Due to significant displacement in the frames it was recommended that temporary works were installed to safeguard the structure from collapse, particularly due to the public highway adjacent to the gable wall (itself displaying signs of movement in distorted stonework). The dry wall construction meant that implementing the current Historic England guidance of restraining cruck frames using anchored cable stays was not feasible, due to any anchor points inducing local distortion in the stones. Therefore, we proposed to remove the roof finishes and realign the frames, strengthening or replacing decayed timbers and installing cable bracing to reduce the potential for future movement. 

The removal of the apex of the frames in the 19th century removed the triangulation of the cruck frames and had allowed the individual rafters to move independently in both directions, which had become noticeable in roof and wall deformations and twisting of the timbers. We proposed to replace this triangulation by installing new oak bracing to the apex, cradling the ridge whilst maintaining the existing material so that the structure could be read appropriately in the future. Care was also taken to reuse as much of the existing material as possible, including the roof slates, rafters, masonry and maintaining the existing locations of peg connections to minimise interventions.  

After the initial scheme had been approved by the National Park and whilst construction was ongoing, several vehicle collisions occurred at the corner of the roadside gable, distorting and moving large stones at the base of the wall. When prevention measures failed we were asked to provide a detail for repair and stitching of the corner using lime mortar and steel bars, to reduce future damage to the wall from vehicles. 

Scalesceugh Hall

We worked closely with Paul Lewis, accredited conservation surveyor, and the local conservation officer during the re-instatement of Scalesceugh Hall following the recent fire damage.

Aira Force

The project at the Aira Force site involved designing two steel walkways to replace areas of footpath. The waterfall platform was located at the base of the waterfall and the walkway along the high level footpath on the northern side of the river. The client was The National Trust and the project lead was Paul Lewis, of Lewis Associates, a local surveyors and heritage consultant.

The waterfall platform was to be suspended over the edge of the plunge pool from raked posts to provide an improved visitor experience. The new walkway was to navigate a narrow section of path that required regular maintenance, reducing the workload for on-site staff, and providing a more enjoyable experience for visitors. The scheme was carefully developed with the project lead and client to ensure it was sympathetic to the existing vernacular. We provided structural input to the initial design and incorporated comments from the curator with regards to the aesthetics required, for example, the balustrades were to appear like the existing estate fencing. The new structures had to have as minor impact as possible to conserve the landscape for future generations. We then developed the design for tender and provided structural assistance throughout the construction stage.


Tweddell & Slater Ltd

Consulting Civil and Structural Engineers
01768 865400
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