The ‘unknowns’ in refurbishment or alteration projects

Refurbishment and alteration projects carry a level of uncertainty that does not exist in new construction projects. The single biggest unknown is the existing structure, what is actually there, how it behaves and whether it will perform as assumed or required for the proposed scheme. Understanding and managing this uncertainty is central to successful refurbishment.

The concealed structure problem

Much of a building’s structure is concealed. Load paths, connections, bearing details and previous alterations are usually not fully visible during early design stages. Assumptions are therefore unavoidable, particularly when assessing important elements such as floor bearing or size, foundation details or depth. However, these ‘unknowns’ introduce risk that only becomes clearer as the project progresses.

Project example - Cambridge

A housing association asked us to inspect a ‘soft and spongy’ balcony floor as part of a large accommodation block which was suspected to be suffering from water ingress. The building was less than ten years old and constructed with timber framing.

The floor finishes and soffit cladding were removed from areas of the balcony, revealing that water ingress had not only softened the floor decking, but had also caused timber deterioration of the primary floor joists. Rot was also present and had begun extending into the main building. The investigation was critical in establishing the nature of the issue, the extent of the issue and the subsequent remedial design required.

Reliability of existing drawings

Existing drawings are useful but are rarely accurate or definitive. Drawings may be incomplete, reflect previous schemes that were not built, or omit later alterations. Original drawings should be treated as guidance rather than confirmation, and even when marked as ‘As Constructed’ or As Built’ it is prudent to have critical elements confirmed by intrusive investigation on site.

Contingency planning

Even with investigation, some uncertainty remains, so effective refurbishment projects acknowledge this and allow for contingency, both technically and commercially. This may involve identifying elements most likely to change, developing alternative structural approaches, allowing for flexibility within the scheme, phasing design decisions. Refurbishment design is often about managing options rather than finalising everything early.

Programme impact

Unknown structure is a common cause of programme pressure. Delays often arise when site findings differ from design assumptions, requiring redesign, client approvals to be sought or additional works being required. Early investigation, clear communication and realistic sequencing reduce the likelihood of disruption.

Project example – Peterborough

An architectural practice asked us to become involved in the alteration of an operational school that involved the formation of new window openings. The works were to be carried out during the school’s summer holiday and the programme was tight. The existing structure was not fully visible during early architectural investigations and so we asked the client to provide us with original drawings for our review. These showed that the existing structure had been designed with steel columns and beams, but crucially with vertical cross bracing present in some of the proposed opening locations.

Our involvement allowed us to identify where it was feasible to retain the proposed openings and where it was not, meaning that the project could proceed without the need for redesign and significant delays that would have resulted.

Without our involvement, the project would not have been able to achieve the desired timescales, and the budget would likely have also been exceeded.

Budget risk management

Structural unknowns are a major driver of cost risk in refurbishment. The most effective approach would be to eliminate uncertainty, but since this is rarely possible, it is crucial to identify where it is present and planning for it. A practical approach would include obtaining early structural feasibility input, carrying out targeted surveys and opening up, and minimising commitments to design before investigation. Refurbishment projects benefit from recognising uncertainty early rather than reacting to it later.

We are extremely experienced in this type of work and have a proven track record of delivering successful refurbishment projects in many different sectors. This includes residential, commercial, education, healthcare and heritage, as well as manufacturing and industrial.

We hope this article has been useful and if you have any questions or would like to discuss any aspect of the work we do, please do not hesitate to contact us.