## 5 Case Studies
### Case Study 1: Willsden Carr South Signal Box Renovation  
A signal box awaiting refurbishment was identified, with an existing repair design dating back to 2014. The structure exhibited extensive rot in its primary timber structural members and side panelling, as documented in Figures 7 and 8. The observed deterioration is consistent with the research findings on common asset failure mechanisms, particularly the impact of insufficient maintenance and material degradation over time. Figure 7: Cont. Figure 8: _Cont._  
Figure 7: Drawings of details and extent of failed material elements of the signal box. A low-load assessment was conducted and confirmed that short-term, inadequately designed temporary works consisting of scaffolding had been previously implemented to maintain the asset's operational status. This approach, frequently employed as a reactive solution, often results in further degradation and unintended damage to historical railway assets. The existing repair design requires the following:  
* The existing paint finish should be stripped throughout. Renovate or renew all defective timbers, including (but not limited to) the replacement of the areas indicated in the drawings. All renewals to the main frame members should be hardwood with a 'like for like' section size. Replace main timber members and infill framing. Prepare and paint all existing and new timber. * Remove existing cladding. Renovate the timber structure (see item 1.3). Reclad on a like-for-like basis. North, east, and west elevation: Prepare all cladding for redecoration. Renovate/renew any defective timbers like-for-like (including the replacement of an area of cladding affected by boring insects at an elevation of W above the landing). Paint all existing and new timber. This case study provided an opportunity to apply the proposed framework to an industrial project in a live railway asset environment. The wider construction industry offers a broad range of contemporary building materials, many of which have the potential to enhance asset management within the rail sector. By applying the framework, a material change could be implemented without full local LPA approval. A review of the product acceptance standard confirmed that building materials were outside the scope of this document. Following this review, a reassessment of the 2014 design was initiated, incorporating wood-grain-effect PVC cladding as an alternative to traditional timber. As a commercial off-the-shelf product, the PVC cladding met all necessary British Standards certification and, through an inquiry with the original equipment manufacturer (OEM), could be customised to match the original RAL colour scheme of the signal box. The use of substitute materials such as PVC in heritage contexts is  
Figure 8: Photograph of the inherited state of the signal box asset with prominent material decay and failure and the temporary support scaffolding. increasingly supported in international conservation practice [41; 42; 43]. This aligns not only with the findings of the Railway Heritage Trust [24] but also with international preservation guidance, such as that issued by the U.S. National Park Service (2023) [44], which supports the use of substitute materials in historic buildings when appropriately matched. The revised designs for replacing the previous wooden cladding with PVC cladding like-for-like and implementing the new material on site are illustrated in Figure 9.  
Figure 9: _Cont._  
In contrast, PVC cladding offered significant advantages in both material consistency and installation efficiency, as illustrated in Table 2. Unlike timber, it did not require seasonal restrictions for painting, as painting timber can only be undertaken in specific weather conditions. This requirement extended the overall installation timeline, adding to project costs. The adoption of PVC cladding eliminated these constraints, streamlining the installation process and contributing to long-term cost savings in both maintenance and material performance.