Procurement Frameworks for Retrofit: Which One Is Right for You?

Retrofit projects demand careful procurement planning. The framework you choose will shape project timelines, costs, quality outcomes and stakeholder relationships. Unlike standard construction procurement, retrofit work carries unique challenges: existing building complexity, occupancy considerations, and the need for specialist PAS2035 competency.

This guide examines the main procurement routes available to housing associations, local authorities and retrofit coordinators in the UK, helping you identify which approach best suits your project scope and constraints.

Understanding Retrofit Procurement Needs

Retrofit procurement differs from new-build in important ways:

• Limited predictability of site conditions and hidden defects
• Occupied properties requiring careful coordination with residents
• Multi-trade sequencing and interdependencies
• Requirement for PAS2035-accredited retrofit coordinators
• Need for specialist supply chains and material availability

Your procurement framework must accommodate these complexities whilst maintaining cost certainty and schedule control.

Main Procurement Frameworks

1. Traditional Lump Sum Contracts

How it works: You obtain fixed-price quotes from contractors based on detailed specifications. The contractor bears most risk.

Advantages:

• Clear cost certainty upfront
• Simpler for smaller, well-defined projects
• Lower client-side project management overhead

Disadvantages:

• High contingency provisions needed for unknowns
• Less flexibility if site conditions change
• Contractors may price risk conservatively, increasing costs
• Can encourage adversarial relationships if variations arise

Best for: Small portfolios of similar properties with relatively straightforward retrofit scopes and minimal uncertainty.

2. Cost-Plus Contracts

How it works: You reimburse the contractor for actual costs (materials, labour, plant) plus an agreed fee or percentage markup. The contractor's profit is transparent.

Advantages:

• Flexibility to adapt scope as site conditions reveal themselves
• Contractor incentivised to work efficiently (not to hide risk)
• Transparent cost breakdown
• Good for complex, uncertain retrofit work

Disadvantages:

• Final cost unknown at project start
• Requires robust cost tracking and audit capability
• Higher client-side oversight needed
• Can lead to cost inflation if not properly managed

Best for: Large multi-property programmes where site conditions are variable and early cost certainty is less critical than flexibility.

3. Design and Build Contracts

How it works: A single contractor designs the retrofit solution and delivers it. You specify performance outcomes rather than detailed designs.

Advantages:

• Single point of responsibility
• Contractor can optimise design and buildability together
• Clear cost and schedule accountability

Disadvantages:

• Less control over design decisions
• Requires clear performance specifications upfront
• Design quality depends heavily on contractor expertise
• PAS2035 compliance must be clearly specified

Best for: Programmes with a defined performance standard (e.g., EPC rating improvement) where you trust the contractor's retrofit expertise.

4. Framework Agreements

How it works: You pre-qualify a panel of contractors and release individual project work against agreed terms and rates. Payment typically follows actual expenditure or job completion.

Advantages:

• Speed—no competitive tendering for each project
• Relationship continuity across multiple projects
• Pre-qualified competency and PAS2035 accreditation
• Easier to scale programmes up or down

Disadvantages:

• Initial setup takes time
• Long-term commitment required to justify contractor investment
• Risk of complacency if performance not monitored
• May require minimum volume commitments

Best for: Multi-year retrofit programmes where you have consistent work and want to build stable supply chains.

5. Term Contracts

How it works: A contractor is retained over a fixed period (typically 2–5 years) to deliver retrofit work as and when required, typically on a cost-plus basis with agreed rates.

Advantages:

• Contractor becomes embedded in your programme
• Reduced transaction costs for repeat work
• Stable relationship supports continuous improvement
• Easy scaling of delivery

Disadvantages:

• Extended commitment with limited exit routes
• Performance must be actively managed throughout
• Requires clear KPIs and reporting mechanisms

Best for: Large housing associations or local authorities planning sustained retrofit delivery over multiple years.

Making Your Choice

Consider these factors when selecting a procurement route:

1. Programme size and duration: Larger, longer programmes justify framework or term contracts; smaller projects suit traditional lump sum.
2. Site certainty: Highly variable conditions favour cost-plus or design-and-build; predictable work suits fixed-price.
3. Cost certainty needs: If final budget is fixed, lump sum or design-and-build work better; if flexibility is acceptable, cost-plus is more efficient.
4. Supply chain maturity: Retrofit expertise in your region may be limited; frameworks help secure qualified contractors early.
5. Client capability: Cost-plus and term contracts require robust cost tracking and performance management from you.
6. Regulatory requirements: Ensure your chosen framework accommodates PAS2035, building regulations certification, and any funder requirements.

Retrofit procurement is not one-size-fits-all. Your choice should reflect your programme scale, the complexity of your properties, available budget certainty, and your organisation's capacity for contract management. Many successful programmes use hybrid approaches—frameworks for volume work, design-and-build for complex cases. Review your choice annually as your programme matures and market conditions evolve.