The editorial team

Every property owner wants a safe, secure, and long-lasting home or investment but too often, trouble is brewing out of sight. From blocked drains to shifting soil and aged utility lines, hidden issues under your feet can threaten structural integrity, aesthetics, health, and value. This guide explores the most common underground threats and explains how proactive assessment, maintenance, and expert solutions can safeguard your property above ground.

1. Common Subsurface Threats to Property

• Underground Drainage Problems

Buried drainage systems are one of the most overlooked yet damaging elements beneath a property. Over time, pipes can become blocked by grease, debris, or invasive tree roots. Cast-iron or clay pipes may also collapse due to age or shifting soil. Such issues result in slow drainage, foul odours, and even sewage backups, all of which damage internal surfaces and pose health hazards.

• Subsidence and Soil Instability

Ground movement is often caused by soil that expands and shrinks (clay), large tree roots, or de-watering from prolonged drought. Subsidence may manifest as cracked walls, uneven floors, doors and windows that no longer close properly, and gaps appearing between walls and ceilings. These signs shouldn’t be ignored, as subsidence can severely compromise foundation stability and property safety.

• Old or Damaged Utility Lines

Many buildings still rely on decades-old service pipes, for water, sewage, gas, or electricity. Corroded or leaking lines raise the risk of contamination, expensive repair bills, or even fire hazards. Seeking out and fixing these lines before they fail is a crucial preventative measure.

• Buried Debris and Construction Waste

Older homes, especially those built on former industrial land or with undocumented renovations may have buried rubble, metal, or old foundations beneath the soil. This debris can cause poor drainage, sinkholes, or damage to new services. Ensuring a clean, stable ground base when renovating or landscaping is essential for avoiding unexpected surprises later.

2. Identifying Warning Signs

Proactive homeowners often spot early indicators of subsurface issues before they materialise into serious damage:

• Cracks in walls, floors, and external brickwork, particularly near ground level or windows
• Patchy dampness or black mould on interior or external walls
• Slow drains, gurgling pipes, or damp patches next to manholes
• Sinking or tilted paving slabs and patios, pools of water, or sagging soil
• Unexplained spikes in utility bills, indicating hidden leaks

Recognising these signs early allows you to address issues before they escalate into major and expensive repairs.

3. The Value of CCTV Drain Surveys

CCTV drain surveys are a highly effective way of locating underground drainage issues without excavation. A camera is guided through your drains, recording footage that expert drainage specialists analyse to locate blockages, root intrusion, collapsed pipes, or faulty connections.

When to use one:

• Recurring drainage problems (such as multiple blockages)
• Buying or selling a property
• Planning landscaping or building over drain routes
• As part of an annual maintenance schedule

These surveys deliver exact diagnoses, save time and cost by avoiding guesswork, and allow for precise repairs (e.g., drain lining or targeted excavation) instead of full-scale digging.

4. Ground Surveys and Structural Assessments

Beyond drains, structural surveys and geotechnical assessments reveal soil composition, load-bearing capacity, and movement potential. Engineers conduct test digs, collect soil samples, and analyse groundwater conditions.

Such assessments are invaluable in situations like:

• Planning extensions, basements, or heavy structures
• Purchasing land or repurposing former industrial lots
• Discovering subsidence during pre-sale inspections

With this data, engineers recommend soil improvements (like compaction or grouting), structural reinforcements, or the installation of drainage mitigation measures, helping you prevent future structural problems.

5. Professional Solutions and Preventive Measures

• Routine Maintenance: Clearing gutters, using drain covers, monitoring soil and pavement levels
• Root-Barriers and Pipe Replacement: Blocking tree roots and upgrading from clay to plastic pipes
• Waterproofing: Adding drainage to basements, installing cavity drainage systems, and installing damp-proof courses
• Ground Works: Installing retaining walls, improving garden drainage, and reinforcing weak soil

Working with qualified professionals ensures accurate diagnosis and effective solutions before minor issues become costly emergencies. Companies like BDS Drainage, known for their quick response and comprehensive repair capabilities, are trusted by homeowners across the UK to handle everything from emergency unblocking to large-scale drain rehabilitation.

6. Legal and Insurance Considerations

• Insurance Coverage: Check whether your building insurance covers subsidence, leaks, or drainage damage; policies can exclude pre-existing or gradual issues
• Local Authority Permissions: Some repairs (like foundation underpinning or uprooting protected trees) may require permissions or specialist inspections
• Property Conveyancing: Subsurface issues must be disclosed during sale processes, neglecting this can lead to legal disputes later

Early identification means greater negotiating power, lower costs, and better outcomes, without surprises after you’ve committed.

7. Why Expert Oversight Matters

Underground threats require careful handling and specialist experience. That’s where expert drainage specialists come in. They offer CCTV surveys, accurate diagnostics, quality drain repairs or replacements, and timely maintenance, all with minimal disruption. Combined with geotechnical engineers and structural experts, they offer comprehensive support from problem finding to solution delivery. Tackling subsurface issues in isolation often leads to overlooked risks, repeated repairs, and escalating costs.

8. Simple Homeowner Strategies

• Frequent visual checks: Monitor cracks, walls, and ground levels seasonally
• Cover Floor Drains: Prevent debris, pets, or leaves from entering pipes
• Avoid heavy planting near service lines or under foundations
• Reconnect drainage run-off: Use soakaways, rain gardens, or water butts to divert rainwater
• Keep soil levels steady: Avoid adding or reducing levels without guidance

Small steps can dramatically reduce risk, especially when paired with professional insights.

Conclusion

Underneath your property lies a world of unseen risks, and it’s your responsibility to address them before they threaten your home’s safety, appearance, and resale value. By understanding subsurface threats and taking preventive action through CCTV drain surveys, ground assessments, methodical maintenance, and professional reinforcement you’ll protect your investment over the long term.

Relying on expert drainage specialists and structural professionals helps locate hidden problems early, enables smarter repairs, and reduces the likelihood of emergency interventions. With proactive strategy and the right support, you can rest assured that what lies beneath isn’t silently undermining what stands above.

Expanding foam is one of those materials that can seem almost magical. You spray it into a gap, and it grows, hardens, and seals up spaces like a pro. It’s used for insulation, filling cracks, and even construction projects. But a common question people ask is: is expanding foam waterproof?

What Is Expanding Foam?

Expanding foam is a polyurethane-based material that expands when exposed to air. It’s commonly used for insulation, sealing gaps, and preventing drafts. You’ll find it in DIY projects and large-scale construction work alike. Some people even use it for crafts or unusual fixes around the home. But before relying on it for waterproofing, it’s worth understanding how it reacts to water.

Does Expanding Foam Repel Water?

Expanding foam does have water-resistant properties, but that doesn’t mean it’s completely waterproof. Once it cures, the outer surface forms a hardened shell that can resist moisture to some degree. However, if constantly exposed to water, especially over a long period, it can start to break down.

Some types of expanding foam are labelled as “closed-cell,” meaning they have a more compact structure that resists water better. Others are “open-cell,” which are softer, less dense, and more likely to absorb moisture. If you need a waterproof solution, the type of foam you choose makes all the difference.

Open-Cell vs. Closed-Cell Foam: Which One Handles Water Better?

Open-Cell Foam

This type of foam is lightweight and flexible. It expands more than closed-cell foam, which makes it useful for filling irregular gaps. But it also has a porous structure, meaning it absorbs water like a sponge. If exposed to moisture, it can degrade over time, making it unsuitable for areas prone to heavy water exposure.

Closed-Cell Foam

Now, this is the option you want if water resistance is a priority. Closed-cell foam is much denser and doesn’t allow water to pass through easily. It’s commonly used in marine applications, roofing, and exterior insulation. While not entirely waterproof, it holds up much better against moisture compared to open-cell foam.

Can Expanding Foam Be Used Underwater?

If you’re thinking of using expanding foam for underwater applications, you’ll need to be careful. Standard expanding foams won’t hold up if they’re submerged for long periods. However, some specialised polyurethane foams are designed specifically for wet environments. These are often used in construction projects involving water tanks, ponds, or even boats.

For example, certain two-part polyurethane foams are created to withstand continuous water exposure. These are more expensive but offer a reliable solution when waterproofing is non-negotiable.

What Happens When Expanding Foam Gets Wet?

If you use open-cell foam and it comes into contact with water, it will likely absorb the moisture, weaken, and potentially become mouldy. On the other hand, closed-cell foam can handle short-term exposure without much trouble, but over time, if water manages to seep into any gaps or cracks, it can lead to deterioration.

If you’re sealing areas that are prone to water exposure, applying a waterproof coating over the foam is a smart move. Many professionals use waterproof sealants or paints to provide extra protection.

Where Should You Avoid Using Expanding Foam?

While expanding foam is incredibly useful, it’s not suitable for every situation. Here are some places where you might want to reconsider using it:

• Basements prone to flooding – Unless you’re using waterproof-grade foam, prolonged exposure to moisture could cause problems.

• Outdoor applications without UV protection – Sunlight can break down expanding foam over time, so it needs to be painted or sealed if used outside.

• Areas exposed to extreme heat – Some foams aren’t designed to handle high temperatures and could break down under intense heat.

How to Make Expanding Foam More Waterproof

If you’ve already used expanding foam but need it to be more resistant to water, there are a few ways to improve its durability:

• Apply a waterproof sealant – Using a silicone-based or polyurethane coating over the foam can add extra protection.
• Use a waterproof paint – Some paints are specifically designed to create a waterproof barrier, making them a good option for sealing foam.

• Choose the right foam from the start – If you’re working on a project where water exposure is a concern, go for closed-cell foam or a waterproof-specific product.

Alternative Waterproof Sealants

If expanding foam isn’t quite what you need, there are other materials that might be a better fit:

• Silicone sealants – Great for waterproofing joints and small gaps.
• Epoxy coatings – Often used for industrial waterproofing, offering a hard and durable finish.
• Rubberised sprays – These create a flexible, waterproof layer and are easy to apply.

The Short Answer

Expanding foam has plenty of benefits, but if you’re relying on it for waterproofing, you need to be careful. Standard foams are water-resistant to an extent, but they’re not fully waterproof unless specifically designed to be. Closed-cell foams offer better moisture resistance, while open-cell varieties absorb water and break down over time.

For the best results, consider using a waterproof sealant over the foam or opt for alternative materials if water exposure is a major concern. Expanding foam is fantastic for many jobs, but knowing its limits helps ensure your project stands the test of time.