Repair vs Replace — Decision Making in Existing Buildings

1. The Structural Integrity Threshold

The first gate in the decision-making process is whether the element can still perform its primary function safely.

• Timber (Rot & Infestation): If more than 30% of a beam’s section is lost to wet rot or woodworm, a “repair” (such as resin injection or steel flitching) may cost more than a like-for-like replacement.

• Masonry (Spalling & Cracking): We assess whether masonry failure is “Aesthetic” (surface-level) or “Systemic” (affecting the load-bearing core). Systemic failure almost always requires replacement to ensure insurance compliance.

• Concrete (Carbonation & Spalling): We use “Cover Meter” surveys to check reinforcement depth. If the steel rebar is significantly corroded, “Patching” is a temporary fix; “Cathodic Protection” or replacement is the professional standard.

2. The Compliance and Regulatory Trigger

Sometimes, the building’s current use forces a “Replace” decision, even if the element is structurally sound.

• Thermal Performance (Part L): In commercial refurbs, existing single-glazed windows may be sound, but their inability to meet U-value targets for an EPC rating of ‘B’ or higher often necessitates a full replacement with high-performance units.

• Fire Rating (Part B): As discussed in Topic 9, an original Victorian door can be “upgraded” with intumescent paint, but if the frame itself is warped or the substrate is too thin, it cannot be certified. In this case, a fire-rated replica is the safer investment.

3. Lifecycle Cost Analysis (LCCA)

We help clients look beyond the initial invoice.

• The “Repair” Trap: A repair might cost £5,000 and last 5 years. A replacement might cost £12,000 and last 25 years.

• The “Hidden” Costs: Replacement often triggers “knock-on” costs—for example, replacing a roof might require a full scaffolding wrap that a minor repair wouldn’t. We provide the cost-benefit analysis for both scenarios so the Asset Owner can make an informed choice.

4. The Sustainability and Carbon Factor

In 2026, Embodied Carbon is a major part of the planning process.

• Retention over Replacement: Retaining existing steel or masonry saves massive amounts of carbon compared to manufacturing and transporting new materials.

• Our Approach: We prioritize “Surgical Repairs.” This involves removing only the failed section of a structural member and splicing in new material, preserving the majority of the original fabric and its embedded carbon.

5. Heritage and “Significance”

In listed buildings, the decision is often taken out of the contractor’s hands by the Conservation Officer.

• Preservation of Fabric: If a feature is of “High Significance,” we must repair it regardless of cost. We utilize specialist subcontractors for lime-plaster moulding, leadwork, and timber carving to ensure the “Patina of Age” is not lost to modern replacements.

The Bloomsbury Approach: Our background in Building Surveying means we don’t just default to the easiest construction path. We provide a “Condition Report” for every major element under question. We would rather advise a client to spend more now on a replacement than have them call us back in two years when a “cheap repair” has failed. This transparency is why we are trusted by long-term asset managers.

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Read our Guide on Listed Building Risks