Stop Building on Assumptions: A Project Manager’s Guide to Eliminating Risk Before Construction
By Paul Reade, Managing Director, Francis Bradshaw Consulting — Chartered Structural & Civil Engineers, Wilmslow, Cheshire | March 2026
The most expensive sentence in construction is “We assumed it would be fine.”
Every project manager has heard it. Usually at the worst possible moment — when the contractor has opened up the structure, the programme is ticking, and the budget is already committed.
A steelwork connection that doesn’t match the original drawings. A floor slab that can’t take the new loading. A retaining wall with movement nobody noticed until the excavator arrived. Ground conditions that bear no resemblance to the assumptions in the tender documents.
These aren’t rare events. They are the predictable consequence of building on assumptions instead of facts.
And the tragedy is that almost every one of them could have been identified, assessed, and resolved on paper — weeks or months before the first pound of construction spend was committed.
This article is for project managers who are tired of managing surprises. It provides a practical framework for identifying the assumptions hiding in your project, converting them into verified facts, and getting the engineering design properly resolved before the big spend begins.
Why Assumptions Are the Hidden Risk in Every Construction Project
An assumption is something your project team believes to be true but hasn’t verified. In construction, assumptions are everywhere, and they’re often invisible until they fail.
Here’s the uncomfortable reality: your risk register probably captures the risks everyone can see — planning delays, material lead times, weather disruption. But the risks that actually blow budgets almost always start as assumptions that nobody thought to question.
Consider the typical assumptions embedded in a retail fit-out or refurbishment project. The existing structure can support the new mezzanine loading. The foundation design from the original building is adequate. The steel frame connections are in the locations shown on the archive drawings (if archive drawings even exist). The floor slab is thick enough for the new racking system. The building complies with current structural codes. CDM requirements are “standard” and won’t affect the programme.
Every single one of these is a risk disguised as a fact. And every single one can be tested, investigated, and resolved before the construction phase begins — if you invest in the preconstruction process properly.
The Real Cost of Unverified Assumptions
Let’s be specific about what happens when assumptions fail during construction, because the costs cascade in ways that initial estimates rarely account for.
The first cost is the direct engineering cost. When a structural problem is discovered during construction, the investigation and redesign typically costs significantly more than it would have at the preconstruction stage. You’re paying for emergency site visits, rushed analysis, and expedited drawing production — all at premium rates.
The second cost is programme delay. While the engineer investigates and redesigns, your contractor is standing. Depending on the scale of the project and the nature of the problem, this can mean days or weeks of lost productivity. On a multi-site retail rollout, that delay doesn’t just affect one store — it ripples through the entire programme.
The third cost is the knock-on effect. Delayed completion means delayed revenue from the asset. It means penalty clauses. It means the next project in the programme gets squeezed. It means your client or stakeholder starts asking questions about your project management capability.
And the fourth cost — the one that’s hardest to quantify — is the erosion of trust. Between you and your client. Between you and your contractor. Between you and the professional team you appointed.
All of this from an assumption that could have been tested for a fraction of the construction budget.
The Assumption Audit: A Framework for Project Managers
The most effective way to eliminate assumptions is to systematically identify them before the design is finalised and certainly before construction is tendered. Here is a practical framework you can apply to any project.
Step 1: List What You Think You Know
Before you commission any design work, sit down with your project team and list everything you’re treating as a fact about the site, the structure, and the brief. Write down every statement that starts with “We believe…” or “The client said…” or “Based on the original drawings…”
These are your assumptions. Some will be valid. Some will be dangerous. You don’t know which until you test them.
Step 2: Categorise by Consequence
Not all assumptions carry equal risk. Ask yourself: “If this assumption is wrong, what happens?”
If the answer is “minor cost adjustment,” it’s a low-priority assumption. If the answer is “programme delay, redesign, contractor standing time, or safety issue,” it’s a high-priority assumption that must be verified before construction begins.
For structural and civil engineering projects, the high-consequence assumptions almost always relate to existing structural capacity and condition, ground and foundation conditions, loading requirements for the new use, compliance with current codes and standards, and CDM and health and safety obligations.
Step 3: Commission the Investigations
This is where the preconstruction investment pays for itself. For every high-consequence assumption, commission the appropriate investigation to convert it into a fact.
For structural capacity questions, that means a structural survey and assessment by a Chartered Structural Engineer. Not a visual inspection by someone without the qualifications to interpret what they’re seeing — a proper engineering appraisal that examines the existing structure, reviews any available drawings, and assesses whether it can accommodate the proposed changes.
For ground conditions, it means a site investigation — boreholes, trial pits, or at minimum a desk study that reviews the geological records and identifies the risks.
For loading requirements, it means a clear, agreed brief that specifies the actual loads the structure needs to support — not a vague description of intended use.
For compliance, it means an engineering review against current codes and standards, including CDM obligations that must be addressed before construction begins.
Step 4: Get the Design Solved on Paper
This is the critical step that too many projects skip or rush. Once you have the facts from your investigations, the engineering design must be developed to a level where the construction solution is defined, costed, and coordinated with the rest of the project.
“Solved on paper” means the structural scheme has been designed, not just sketched. It means the connections, the foundations, the load paths, and the temporary works have been considered. It means the design has been coordinated with the architect’s layout, the M&E engineer’s requirements, and the contractor’s preferred construction sequence.
It means the construction team can price the work with confidence, build it without surprises, and complete it without redesign.
This is the moment where the engineering fee delivers its greatest return. A properly developed preconstruction design costs a small percentage of the overall project budget but can prevent cost overruns that dwarf the original engineering fee many times over.
Step 5: Verify and Close the Loop
Before you commit to the construction phase, review your original assumption list. For every high-consequence assumption, confirm that it has been tested, verified, and resolved in the design. If any remain open, don’t proceed until they’re closed.
This is a simple discipline, but it’s remarkably rare. Most projects move from design to construction with a handful of unresolved assumptions still embedded in the programme. Each one is a latent risk waiting to surface.
The Preconstruction Investment: What It Actually Looks Like
Let’s demystify what “proper preconstruction engineering” involves, because it’s not as expensive or time-consuming as many project managers assume (there’s that word again).
A typical preconstruction structural engagement might include an initial site visit and structural appraisal of the existing building, review of any available historical drawings and records, a structural feasibility assessment for the proposed works, a developed structural scheme design with outline specifications, CDM pre-construction information and Principal Designer input, and a coordinated package ready for construction pricing.
For a standard retail unit or commercial refurbishment, this work can often be completed within a few weeks and for a fee that represents a small fraction of the overall construction cost.
Compare that to the cost of discovering the same issues during construction — emergency investigation fees, redesign costs, contractor delay claims, programme disruption — and the case for preconstruction investment is overwhelming.
A Note on CDM: The Assumption That Can’t Be Ignored
The Construction (Design and Management) Regulations 2015 place specific duties on clients and designers to manage health and safety risks through design. These duties apply from the very start of a project, not from the start of construction.
Yet CDM compliance is one of the most commonly deferred assumptions in project management. “We’ll sort CDM when the contractor is appointed.” “The Principal Designer role is just paperwork.” “Health and safety is the contractor’s responsibility.”
Every one of these statements is both wrong and dangerous. CDM requires that design risks are identified and eliminated or controlled before construction begins. That means structural designers need to be considering buildability, temporary works, and residual risks as part of the preconstruction design — not as an afterthought once the contractor is on site.
Getting CDM right from the start is not just a legal obligation. It’s a practical one. When health and safety is designed into the scheme from the outset, the construction phase runs more safely, more efficiently, and with fewer costly interventions.
What Good Looks Like: The Preconstruction Mindset
The project managers who consistently deliver on time and on budget share a common trait: they invest in certainty before they commit to spend.
They don’t treat structural engineering as a commodity to be appointed at the last minute. They bring the engineer into the project early — at feasibility or concept stage — and use that expertise to identify and resolve the unknowns before the design is finalised.
They don’t accept assumptions. They test them. They ask: “What do we actually know? What are we assuming? And what could go wrong if we’re wrong?”
They get the design solved on paper — properly, thoroughly, and in coordination with the rest of the project team — before the first pound of construction spend is authorised.
And when construction begins, they manage a project built on facts, not hopes.
How Francis Bradshaw Consulting Supports Preconstruction Risk Management
Francis Bradshaw Consulting is a Chartered Structural and Civil Engineering consultancy established in 1977, based in Wilmslow, Cheshire, and serving clients across the North West, North East, Yorkshire, Midlands, and throughout the UK.
We specialise in helping project managers get certainty before construction. Our preconstruction services include structural surveys and condition assessments of existing buildings, structural feasibility studies for proposed alterations and extensions, full structural scheme design coordinated with architectural and M&E teams, CDM Principal Designer services from project inception, and clear, pragmatic engineering advice that helps you make informed decisions.
We work across the retail, housing association, industrial, and local authority sectors, and we’ve delivered structural and civil engineering on over 50 retail stores for national brands.
Our approach is simple: bring us in early, and we’ll help you identify the assumptions, convert them to facts, and get the design solved on paper — before the big spend begins.
Ready to Eliminate the Assumptions in Your Next Project?
If you’re a project manager planning a construction project and you want to get the engineering right before you commit to the build, we’d welcome the opportunity to talk.
Contact Francis Bradshaw Consulting:
- Location: Dean Row Court, Dean Row Road, Wilmslow, Cheshire SK9 2TA
- Email: team@francisbradshaw.co.uk
- Phone:01625548551
- LinkedIn: https://www.linkedin.com/company/francis-bradshaw
- Web: www.francisbradshaw.co.uk
Chartered Structural & Civil Engineers | IStructE | ICE | SSIP Accredited | Avetta Accredited | Established 1977
Frequently Asked Questions
What is preconstruction risk management?
Preconstruction risk management is the process of identifying, assessing, and mitigating potential problems before construction begins. It involves turning assumptions about site conditions, structural capacity, and design feasibility into verified facts through surveys, engineering analysis, and early-stage design work.
Why do construction projects go over budget?
Most construction cost overruns originate from assumptions made during the design phase that were never verified. Common examples include assuming existing structures can support new loads, assuming ground conditions are favourable, or assuming approvals will be straightforward. When these assumptions fail during construction, the cost of fixing them is significantly higher than investigating them upfront.
When should a structural engineer be appointed on a construction project?
A structural engineer should be appointed at the earliest concept stage — before designs are finalised and before the client commits to a construction budget. Early structural input prevents costly redesigns, confirms whether existing structures can accommodate proposed changes, and ensures the design is buildable and compliant before the big spend begins.
What is the difference between an assumption and a risk in construction?
An assumption is something you believe to be true but haven’t verified. A risk is a potential event that could negatively impact your project. Every unverified assumption is an unmanaged risk. The goal of preconstruction planning is to convert assumptions into facts through investigation and engineering analysis — thereby eliminating the associated risk.
How much does a preconstruction structural survey cost compared to fixing problems during construction?
A preconstruction structural assessment typically costs a small fraction of the construction budget. However, discovering structural problems during construction can add significantly to engineering costs, plus programme delays, contractor standing time, and potential redesign fees. The return on investment for early structural investigation is substantial.
