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Basingstoke & Deane Planning Civic Offices London Road Basingstoke RG21 4AH

15th June 2020

Land adjacent to Nunnery House – Design Feasibility

Goss & Partners were appointed by Mr S Woodman to undertake a design feasibility assessment of the agricultural building at the subject site, to determine the structural layout and design scheme in relation to the existing foundations and structure for the suitability of conversion to domestic accommodation.

Roof Loads At this current time, the roof is made of 4 steel, duo-pitched portal frames at 4.5m centres spanning 12m to the centreline of the columns. In order to fall in line with advice given by the officers at Basingstoke & Deane Planning Authority, we have to show evidence of how the conversion will not implement the suitability of the steel frame and cause large scale works to reinforce and renew structural assets on the subject site. Although the roof loading was marked as being ‘almost at capacity’, we have implemented a scheme which would allow the existing structure to take the new loading. After analysing the steel frames, we decided to add 4 steel columns to the centre of each portal frame. These columns work in sync with a new steel ridge beam which would be welded to the underside of the portal frames and supported by the addition of the steel columns. By opting for this approach, there is a minimal amount of structure being added to the scheme, which would allow for the existing steel portals to remain in their entirety. After reviewing the structural assessment, which was provided by Modulus Structural Engineering, we have used the predicted loadings to base our analysis accordingly. According to their assessment, the existing roof loadings were currently giving a mass of 0.21 kN/m2, this was made up of the corrugated concrete sheets and metal purlins. The engineer’s assessment had predicted a new roof loading, based on the provisions for residential accommodation to be 0.66 kN/m2. However, after careful consideration and material exploration, we have come up with a lightweight roofing system which would bring the predicted mass down to 0.45 kN/m2. This composition has been made up of the following elements: Plaster & Skim 0.15 kN/m2 Services 0.10 kN/m2 Metal Purlin Clips 0.05 kN/m2 Existing Steel Frame N/A Metal Purlin Clips 0.05 kN/m2 Insulated Roof Panel 0.10 kN/m2 By using an architectural insulated roof panel, we can provide a lightweight roof system which is highly efficient and durable, as well as reducing the predicted mass, thus lowering the predicted movement of structure and foundations.

Façade Detailing Whilst exploring the wall composition required for the conversion of this agricultural building and adhering to guidance made by the structural engineer’s report, we explored avenues which utilised the existing steel frame by mitigating the possibility of lateral deflection. By introducing mitigation measures, we are able to protect the existing steelwork of the barn and use this to its full capacity, without the need to restore and renew the structure and any foundations.

GPIn order to mitigate the deflection of the structure under the new loading, we have specified a cladding system which is non-brittle, therefore if and when any deflection and movement occurs albeit in the superstructure or the foundations, the façade can withstand the forces and act accordingly. This is why we have introduced a featheredge timber cladding, which is horizontally lapped. Softwood weatherboard is not only an environmentally friendly approach and would also give a lower embodied energy, if supplied by local timber mills, it is also resilient and durable. Lapping the weatherboard allows for movement in the boards, whilst preserving the integrity of the material and also not damaging the aesthetical values of the material.

Material Usage In order for any design proposals to fit into the surrounding environment and complement the existing listed buildings around the conservation area, careful consideration was taken to select materials which would preserve the look and feel of the existing agricultural building. Below is a selection of materials which would look to be specified for any potential development to tie in with the existing layout of the subject site:

Conclusions Overall, in response to comments made by the planning officers about the suitability of the proposed conversion and the likely impact it would have towards the new structure, we have detailed an approach that would appear to be more favourable. By implementing these strategies in correlation with an internal layout which acted independently from the superstructure, it would create a more viable conversion which would look to reinforce only where necessary, the roof ridge, to withstand an increased loading, whilst offering a very minimal solution which relied on very little additional structural steel work. In our opinion, this would be deemed more acceptable towards the planning authority and restore the ‘conversion’ title that our client is trying to achieve here, due to the fact that we have proposed a lighter roof structure and a façade system which works in parallel with the steel frame, and also specified a material usage that is environmentally friendly, has a low embodied energy, and preserves the aesthetical values of the site by designing something that is in keeping with the surrounding environment. Yours sincerely, Alfie Goss On behalf of Goss & Partners

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