Planning Uncertainty in the UK: Permitted Development, Flood Risk & Construction Challenges | TMDP LLP

When the Rules Aren’t Clear: Planning & Construction in Today’s UK Landscape

Understanding Permitted Development, flood risk data, and rising construction complexity

At TMDP LLP, we work at the sharp end of UK planning and construction.

What we are seeing more frequently is not a change in legislation; but a change in interpretation.

Across residential, heritage, and commercial projects, clients are encountering increased uncertainty around planning decisions, greater reliance on national datasets, and a more risk-averse approach from local authorities. The result is delay, added cost, and avoidable frustration.

This blog explores what’s happening — and how informed professional advice can make the difference.

Permitted Development: When Compliance Isn’t Enough

Permitted Development (PD) rights are designed to provide clarity and consistency. They are set out in legislation, supported by Planning Practice Guidance (PPG), and widely relied upon for domestic extensions and outbuildings.

However, we are increasingly seeing:

• Certificates of Lawful Development refused despite full dimensional compliance

• “Incidental to the enjoyment of the dwellinghouse” interpreted as a question of scale rather than use

• Decisions influenced by concerns over future misuse, rather than the proposal itself

This runs counter to established planning guidance, which makes clear that use — not size alone, determines whether development is incidental.

At TMDP, a growing part of our planning role involves re-anchoring decisions back to policy, guidance, and case law, ensuring applications are assessed lawfully and proportionately.

Flood Risk Mapping: Data vs Local Knowledge

Flood risk assessments are another area where national datasets increasingly dominate decision-making.

While Environment Agency mapping and modelled data are valuable tools, they are not infallible.

We regularly encounter sites:

• Flagged as high flood risk with no recorded flooding history

• Where long-standing local knowledge contradicts modelled outcomes

• That suddenly require costly specialist reports to challenge baseline assumptions

Planning should remain evidence-led and proportionate. Over-reliance on datasets without site-specific understanding can unnecessarily burden small-scale and low-risk developments.

Rising Construction Costs & Changing Client Behaviour

Alongside planning uncertainty, the construction landscape has shifted dramatically.

With costs continuing to rise, many clients are:

• Self-managing projects

• Appointing individual trade contractors

• Reducing reliance on traditional main contractors

While this approach can reduce overheads, it also removes the professional buffer that historically managed sequencing, coordination, and risk.

In response, TMDP has evolved how we support clients:

• Clearer, more detailed technical design packages

• Defined scopes of work for individual trades

• Ongoing project and construction management advice

Good architecture today is not just about design — it’s about deliverability, clarity, and risk reduction.

A Calm, Evidence-Led Planning & Construction Approach

Across planning and construction, the common thread is uncertainty.

Our role as architects and project managers is to:

• Translate planning policy into practical advice

• Challenge decisions respectfully using evidence and guidance

• Protect clients from unnecessary delay and cost

• Keep projects moving forward when the process becomes complex

With over 20 years of experience across the Midlands and the UK, TMDP brings a measured, professional approach grounded in regulation, experience, and local knowledge.

Considering a Project?

If you are:

• Unsure whether Permitted Development applies

• Facing planning resistance or inconsistent advice

• Concerned about flood risk constraints

• Navigating a self-managed or complex build

Early advice can save significant time and cost.