Why land quality matters in residential development

Land quality issues can hold up housing projects, drive up costs, risk the reputation of a project and cause issues with regulation. For developers, landowners and consultants, spotting these risks early makes all the difference. Our land quality team can get involved at any point from the early technical review, but works most effectively when embedded within projects from day one. Using decades of experience, we review technical reports for warranty compliance to provide confidence in matters related to the assessment of site conditions and buildability, supporting safe, long-lasting homes.

In this article, we’ll explore the most common land quality issues, what we assess and consider for proposals aimed at managing them, and how early engagement can help keep your project on track.

Common land quality issues for residential sites in the UK

Unlocking brownfields or marginal land for new homes often comes with hidden challenges beneath the surface. From contamination to unstable ground, these issues can impact structural safety, delay construction and make it harder for you to qualify for our Buildmark warranty.

Our Land Quality Service helps you address those risks early so that you can build with confidence.

Here are some of the most common issues our specialists encounter.

Contamination: invisible threats beneath the surface

Land contamination from past commercial and industrial use is one of the biggest risks on brownfield land. Substances like hydrocarbons, heavy metals or solvents can affect human health, groundwater and the wider environment.

If not assessed and remediated, contamination could put future residents at risk, damage landscaping plans or make foundations unsuitable. For warranty purposes, we need to see that contamination risks have been properly identified, addressed and verified using multiple lines of evidence. Quick fixes like gas membranes aren’t enough.

Poorly justified assessments or mismatched mitigation strategies are a common cause of delay. If you engage with our Land Quality Service, our specialists will work as part of your team to make sure everything is in order and warranty-eligible.

Made ground: the risks of unpredictable fill

Sites that have been previously developed or reprofiled often have made ground that is a mix of soil, rubble, waste or man-made fill. It's usually very different to the ground surrounding it, and hard to predict without investigation. 

Building on poorly controlled made ground can lead to:

• uneven settlement
• structural movement
• reactive ground conditions
• foundation failures.

We pay close attention to the fill’s origin, moisture levels and compaction levels. We also check for buried obstructions and see whether any engineered solutions are feasible. This is all part of our early-stage assessment.

Asbestos presence in soil: dealing with a legacy hazard

Asbestos-containing materials (ACMs) are still found on former industrial or demolition sites, even when clean-up work has taken place.

Asbestos is both a health hazard and a regulatory challenge. Often, you need soil remediation to deal with the risk. To move forward with warranty approval, we need clear, validated evidence that the asbestos has been dealt with or removed as necessary.

Slopes and gradients: managing geotechnical instability

Steep or uneven sites can raise a range of geotechnical and drainage concerns. Potential issues include:

• slope instability
• poor surface water management
• increased erosion after clearance or earthworks.

If left unmanaged, these risks can lead to:

• structural movement
• inaccessible or unsafe sites
• drainage systems that don’t work.

To de-risk a site with varied topography, we need to see clear geotechnical assessments, slope stability modelling where necessary, and foundation designs that match site-specific conditions. Poor design at this stage can lead to delays, redesigns and extra costs later.

Unknown underground obstructions: what lies beneath

Unexpected underground obstructions sometimes only come to light when a site is being excavated, and don't appear on historic maps. These can include:

• redundant foundations
• buried tanks
• old drainage equipment
• former basements.

Finding them late can lead to major delays and redesigns. That's why we encourage an intrusive investigation early on. Identifying obstacles early can help avoid costly disruption and support a smooth warranty process. 

New risks, according to our land quality specialists

Our land quality specialists keep a close eye on new and evolving issues that could affect low-rise housing developments. Below are some of the areas we’re seeing more frequently and how we work with developers and consultants to tackle them early.

Engineered fill

There are new rules around filling or replacing of ground like old quarries to bring the ground level and ready to build on. If it is not done properly, it can cause structural problems later and delay the building and warranty sign-off.

PFAS

Short for per- and polyfluoroalkyl substances, these are man-made chemicals that don’t break down easily and can be harmful. They are often found on old military and industrial sites, locations of historical fires and in places associated with fertilisers and pesticide use. This issue can be tough to deal with and needs close attention in ground assessments.

Medicines in groundwater

This is becoming more of an issue, especially near old landfills or sewage systems. Trace levels of antibiotics, hormones, painkillers and antidepressants can get into water through wastewater, farm runoff (from medicated livestock) and leaking landfill sites. These traces can harm wildlife and will be picked up by the Environment Agency. We will need to see site-specific risk assessments before we can move forward with warranty approval.

What to do early on: advice for developers

Many problems we see come from poor ground investigations or unclear reports. Getting us involved early can help you spot risks, avoid delays and save time and money.

Talk to us before you buy or design

Our early-stage reviews can help you understand land risks before you commit. It’s a cost-effective way to get ahead of problems and build confidence in your plans.

Make sure the site investigation is thorough

If you're dealing with brownfield or tricky land, a site investigation is a must. It should:

• look at both contamination and soil stability
• include monitoring or modelling if needed
• be tailored to the layout you’re planning.

Generic or outdated reports often cause delays. We need a clear picture of what's in the ground and how it affects your designs.

Keep your reports clear and joined up

We often find that delays are caused by conflicting or confusing reports. What we need to see is:

• a robust conceptual site model
• clear identification and management of risks
• recommendations that are properly backed up
• consistent terms, site names and boundaries
• reports signed off by someone qualified.

Also, if the site layout changes after the initial investigation, make sure the reports are updated.

How our Land Quality Service works

Our Land Quality service gives you a clear, step-by-step process to find out and certify whether the land is suitable for building. Each stage helps reduce the risk and gives you more certainty as the project moves forward.

Risk check

At this stage, consultants carry out desk studies, site investigations and risk assessments. We review their work and highlight any gaps that could affect warranty approval, like missing evidence, unclear findings or assumptions that don’t stack up.

Proposing solutions

This is when consultants will suggest ways to fix the issues. We check that their plans match the risks on site and deal with them properly. We appreciate there are differing requirements for geotechnical and geo-environmental needs, so we ensure that approaches are compatible and don't cause unintended consequences. Getting us involved early can help avoid delays and extra costs later.

Certification

After the ground has been fixed and any engineering work is done, consultants need to show clear evidence that the site is ready to build on. This usually means providing validation reports, drawings and other documents. We check that everything’s been done as agreed, the reports are clear and the site meets our standards for warranty approval.

Professional insight: the benefits of partnering with us for land quality

Land Quality Specialist David Jacob states that partnering with NHBC offers “a pathway to warranty” through three key areas: time, quality, and cost. Early involvement means we “minimise unexpected delays” and can provide “unfettered access” advice. When included early in the development process, the NHBC team can provide the “technical clarity” that will prevent designs being rejected late in the process: “We’d much rather they came to us, make us part of that team”.

For landowners, investors and builders, NHBC being involved means they can “sell this piece of land… for its maximum value” and have “confidence that the land will be acceptable to our warranty”.

David continues: “We often say that we have a helicopter view… we have no personal investment in the site, so we ask those difficult questions.”

That independent, early-stage challenge helps ensure ground risks are remediated appropriately: “Ultimately, we get a de-risked site that’s really for the betterment of everybody involved”.

By partnering early, developers can identify risks, validate remediation and prepare for a successful warranty outcome. “We provide additional confidence that the land will be acceptable to our warranty and minimise the potential for unexpected ground conditions.”

We’re here to help you build on solid ground

We’re not the regulator or the planning authority; we’re here to make sure the land is suitable for building long-lasting, high-quality new homes that can obtain our warranty.

We work with you and your consultants to provide clear advice and early input. Involving us from the start can help avoid delays, extra costs or unwanted surprises later down the line. We help developers navigate complex sites with confidence.