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Sept & Oct Social Media recap

🏗️ Project Update: Prestigious New Development in St John’s Wood, London 🏡

We’re proud to be part of this high-end residential project in St John’s Wood, where the transformation involves the demolition of an existing property and the construction of a stunning new home designed to the highest standards.

📍 Our team is making great progress with the cavity membrane installation in the expansive basement. With multiple levels to work through, our skilled technicians are now focusing on the upper sections, ensuring every detail is executed with precision.

This is a complex and exciting build, and we’re thrilled to see it taking shape. Big thanks to our dedicated team on site, your hard work and expertise are driving this project forward!

🔧 Project Spotlight: Haslemere Swimming Pool Basement 🌿

We’re proud to be delivering the full waterproofing package for a luxury basement swimming pool in Haslemere, complete with changing rooms, kitchen, and dining area.

💡 Waterproofing Highlights
This fully buried structure sits beneath a landscaped garden and green roof, demanding zero tolerance for water ingress. Our solution includes:

Crystal Coat: Cementitious crystalline slurry applied to internal walls and slab to block capillary paths.
Type C System: Cavity membrane, perimeter drainage, and twin pump system with battery backup — all compliant with BS 8102:2022 Grade 3.

🧪 Deck Protection
Above the basement, we applied our PolyM liquid waterproofing membrane , a seamless, flexible coating that resists root penetration and accommodates movement, ideal for green roof applications.

🛠️ Installation is near completion almost, ready for the next phase,

We’re proud to be contributing our specialist waterproofing expertise to the restoration of the historic 20th Century Theatre in London, a venue soon to be revived as a vibrant space for music, dance, and stage productions.

Our experienced surveyor has designed a bespoke internal waterproofing system tailored to the unique requirements of this heritage building. The system includes:

Application of a lime inhibitor to the internal walls and floor surfaces, which helps neutralise the high alkalinity often found in lime-based substrates, ensuring compatibility with modern waterproofing materials.
Installation of a cavity drain membrane system, which manages water ingress by directing it to a controlled drainage point, preserving the integrity of the structure while maintaining breathability, essential in older buildings.

Once complete, the space will be warm, dry, and protected, ready to be restored to its former glory and enjoyed by future generations.

Our in-house aftercare team will arrange regular system checks and maintenance, so the client will always be cared for by us,

Data Centre Waterproofing – Oct Newsletter

Waterproofing in Data Centre Construction: A Critical Risk Management Strategy

With the surge in demand driven by AI and recent deals with major US tech giants, the data centre market is set to expand rapidly. But with growth comes risk—and waterproofing is one of the most critical yet overlooked aspects of data centre construction.

Why Waterproofing Matters

Water ingress, moisture migration, and gas penetration are among the most common causes of construction delays and post-completion failures. These issues can lead to costly downtime, especially for data centres where uninterrupted operation is essential. Main contractors risk millions in liquidated damages if waterproofing fails during or after construction.

Data centres require precise environmental control. Even minor leaks or humidity spikes can compromise sensitive equipment, delay commissioning, or breach service-level agreements.

That’s why compliance with British Standards and the Building Safety Act isn’t just a statutory requirement, it’s a vital safeguard for the design team, contractor, and client.

The Myth of Manufacturer Guarantees

British Standards (BS 8102 for waterproofing and BS 8485 for gas protection) and the Building Safety Act demand rigorous design and installation practices. Manufacturer guarantees alone do not meet these standards. In fact, no successful claims have ever been made against a manufacturer’s waterproofing guarantee, liability always falls on the installer. If you're not using a specialist waterproofing contractor with appropriate insurance, you don’t have a valid guarantee, and you’re not compliant, regardless of what the manufacturer promises.

Key Compliance Requirements

To meet British Standards and mitigate risk, the following must be in place:

Waterproofing design must begin at RIBA Stage 2, led by a qualified waterproofing design specialist
A Golden Thread of information must be maintained throughout the project lifecycle
All works must be carried out by trained, insured specialists with a minimum of £10 million Professional Indemnity (PI) cover
Service entries must be designed and installed early to ensure gas and water tightness from the outset
Gas protection is mandatory for most below-ground structures, especially in brownfield or contaminated sites
Inter-floor waterproofing and service penetration detailing must be handled by specialists to avoid weak points in the structure.

Only a specialist design-and-install company with a proven track record and genuine guarantees can deliver fully integrated waterproofing and gas protection systems.

Why MacLennan?

MacLennan has successfully delivered thousands of below-ground projects, including complex multi-storey basements in challenging environments. Our credentials include:

Full design liability backed by extensive experience
Insured long-term guarantees on workmanship and materials
Integrated systems combining structural waterproofing and gas protection
Qualified, experienced, and insured installers

Unlike manufacturers, MacLennan takes full responsibility for design, supply, and installation using our own trained staff. Our designers have real-world site experience, something manufacturers lack, often resulting in impractical or flawed designs.

We can demonstrate zero basement waterproofing failures across 200+ projects annually. Manufacturers can’t make that claim because they don’t install or guarantee the work.

Ongoing Support & Monitoring

MacLennan offers:

A dedicated aftercare department with qualified electricians for pump and backup system servicing
Remote monitoring services for critical components like batteries, floats, and alarms, alerting you to potential issues before they become problems.

Contact our technical design team today to take the risk out of your data centre waterproofing.

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July & August Social Media Recap

🔹 Basement Waterproofing in Chelsea, London

We’re proud to share that MacLennan has been appointed to deliver the waterproofing design and installation for a significant new basement development in Durham Place, Chelsea.

This project comes with a unique backstory — the original property was tragically damaged beyond repair following the collapse of a neighbouring building and was subsequently placed under a Dangerous Structures Notice.

Working alongside the highly respected team at Forcia, specialists in complex and high-risk structural work, we ensured the safe demolition of the existing structure and the installation of piling to secure the new basement box.

Following a detailed site inspection, our experienced and qualified surveyor recommended a dual waterproofing strategy in accordance with BS8102:2022 – the British Standard for protecting below-ground structures from water ingress.

🔹 Primary Protection: A cementitious coating applied to the internal surfaces below ground to reduce water penetration.

🔹 Secondary (and most critical) Protection: A Type C Cavity Drain System – a maintainable and therefore guaranteeable solution that forms the backbone of long-term waterproofing performance.

This approach ensures robust protection and peace of mind for the client, aligning with best practices and industry standards.

🔹Waterproofing a Historic London Landmark

We were recently contacted to provide our specialist waterproofing design for a large existing basement beneath the Grade II listed Marlborough Head pub in London, which is undergoing a major renovation.

Our team has now completed the installation of a comprehensive cavity drain system throughout the basement and vaulted areas. 🎥 The video offers a walk-through of the newly installed system, showcasing how this once damp and unusable space is being transformed into a dry, habitable environment, ready for its future purpose.

As more and more existing basements in London are being converted into living or commercial spaces, it’s essential to involve waterproofing experts early in the process. Consulting with professionals from the outset, ideally from RIBA Stage 3, ensures that the design is tailored to the unique challenges of each property.

✅ At MacLennan, we take full responsibility for the waterproofing design, backed by our extensive experience and £10 million PI cover. We don’t just install systems, we take the risk out of waterproofing.

🔹 New Project Introduction: Garland Park with Esquire Developments

We’re excited to be working with new clients, Esquire Developments, on the Garland Park project, transforming the former Benenden Hospital brownfield site into a stunning development of 87 new homes.

Our team recently visited the site to review groundwork progress ahead of our installation phase, ensuring everything is in place for our technicians to begin waterproofing.

🔹 MacLennan has been appointed to design and install waterproofing systems for 15 high-end basement units within a terrace.
🔹 Our CSSW & WDS qualified design team has specified a dual waterproofing approach, including a cavity drain system, to ensure the solution is repairable, maintainable, and fully compliant with BS8102:2022 for Grade 3 habitable spaces.
🔹 Each basement will be independently guaranteed, offering tailored protection for every property.

We’re proud to deliver robust, future-proof waterproofing solutions backed by our expertise and industry-leading guarantees.

Resin Injection August 2025 Newsletter

Basement waterproofing remains a critical concern for construction professionals, especially in urban environments where below-ground structures are increasingly complex. Among the most effective and minimally invasive solutions available today is resin injection, a technique that offers both structural reinforcement and watertight sealing.

Resin injection is normally required where the primary or existing waterproofing has failed. The structure is leaking. A remedy is required.

What Is Resin Injection?

Resin injection involves the use of polyurethane , Acrylic or epoxy resins to seal cracks, joints, and voids in concrete structures. The process typically includes:

Identifying the source of water ingress
Drilling ports along the affected area
Injecting resin under pressure, allowing it to expand and fill the voids
Curing, which forms a watertight seal that adapts to future movement

Polyurethane resins are particularly effective for active leaks, as they expand upon contact with moisture. Epoxy resins, on the other hand, are ideal for structural repairs due to their high bonding strength acrylic resins are often used where movement is likely.

Other resin options are available for different scenarios such as curtain wall installations and movement joints.

Resin Injection - Luton street 15.02.21 (3)

Diagnosing and Specifying the Solution

Once the source of a leak is diagnosed by the MacLennan surveying team, a tailored specification is prepared for remediation. This ensures that every intervention is based on a thorough understanding of the structure and the nature of the ingress.

Large voids are chased out and filled with watertight concrete repair mortar.
Cracks and deep voids are injected with our polyurethane resins, which react with water to seal the area permanently, preventing further ingress.

Tackling Joint Leaks with Precision

Very often it is joints, rather than cracks, that are the primary source of leaks in basement structures. The resin injection of construction joints must be carefully considered, as these joints can be designed to accommodate movement. Incorrect material selection or overfilling can lead to future complications.

MacLennan’s resin injection engineers bring over 30 years of experience to this highly specialised form of waterproofing. Our expertise have been applied to some of the most technically challenging projects in the UK.

Why It Matters for Basement Projects

Basements are especially vulnerable to water ingress due to their below-ground location. Traditional waterproofing methods, such as external membranes or tanking, can be disruptive, costly, and impractical or impossible for retrofit projects. Resin injection offers several advantages:

Non-invasive: No need for excavation or extensive demolition
Fast application: Most jobs can be completed within hours
Durable: Resins are resistant to chemicals, movement, and long-term moisture exposure
Cost-effective: Reduced labour and material costs compared to traditional methods

Applications in Design and Remediation

For architects and engineers, resin injection provides flexibility in both new builds and retrofit scenarios. It can be used to:

Seal construction joints and cold joints
Repair cracks caused by settlement or thermal movement
Reinforce structural integrity in aging concrete
Complement other waterproofing systems as a secondary barrier

Conclusion

Resin injection is not a one-size-fits-all solution, but when applied correctly, it offers a high-performance, low-disruption method for basement waterproofing. For construction professionals, understanding its capabilities and limitations is key to delivering resilient, watertight structures.

Resin injection will never be the primary waterproofing except in White tank scenarios for maybe a Carpark or tunnel.

For habitable construction where finishes are to be installed. Resin injection will be used to stop water ingress prior to installation of the waterproofing system.

Comprehensive Support from Survey to Completion

MacLennan surveyors investigate, report, and recommend the correct course of action, supplying fully itemised costs for all aspects of the work—including coordination with main contractors where necessary. The work is then carried out to the highest standards, leaving clients with the confidence that their basement is now fully watertight.

Please watch our resin injection video below...

JUNE Social Media Post Roundup

🔹Large Deck Over an Underground Car Park:

🔍 𝗦𝗶𝘁𝗲 𝗦𝘂𝗿𝘃𝗲𝘆 & 𝗪𝗮𝘁𝗲𝗿𝗽𝗿𝗼𝗼𝗳𝗶𝗻𝗴 𝗔𝘀𝘀𝗲𝘀𝘀𝗺𝗲𝗻𝘁
Our experienced surveyor recently visited this Bournemouth, mid-1970s purpose-built apartment complex comprising two 7-storey towers with a shared basement car park, to carry out a comprehensive inspection following reports of water ingress.
💧 𝗜𝘀𝘀𝘂𝗲 𝗜𝗱𝗲𝗻𝘁𝗶𝗳𝗶𝗲𝗱:
Water penetration was observed through the roof slab of the basement car park. The original deck was constructed using asphalt membranes, which are known to degrade under prolonged UV exposure. Over time, thermal expansion and contraction can lead to fatigue and cracking—especially at high-stress areas such as corners, structural junctions, and upstand details.

🔎 𝗞𝗲𝘆 𝗜𝗻𝘀𝗶𝗴𝗵𝘁:
It’s important to note that visible leaks on the underside of a concrete slab don’t always indicate the exact point of water entry. Water can migrate through construction joints, and movement joints before becoming visible below.
🏗️ 𝗦𝘁𝗿𝘂𝗰𝘁𝘂𝗿𝗮𝗹 𝗢𝘃𝗲𝗿𝘃𝗶𝗲𝘄:
The basement structure consists of reinforced concrete downstand beams supporting a 150mm thick slab. The ground-bearing slab includes perimeter edge thickenings and reinforced concrete walls to retain surrounding ground levels. Our inspection also highlighted the need for upstand and concrete repairs in several areas.
We’re now working closely with the client to develop a robust waterproofing solution tailored to the unique challenges of this buried deck system.

🔹Semi-Basement Extension, Salisbury: Following our pre-construction waterproofing survey, our technicians are now on site installing a 𝗧𝘆𝗽𝗲 𝗖 𝗰𝗮𝘃𝗶𝘁𝘆 𝗱𝗿𝗮𝗶𝗻 𝗺𝗲𝗺𝗯𝗿𝗮𝗻𝗲 𝘀𝘆𝘀𝘁𝗲𝗺 to protect the newly built semi-basement extension at this 𝗚𝗿𝗮𝗱𝗲 𝗜𝗜 𝗹𝗶𝘀𝘁𝗲𝗱 property in Salisbury.
Although not a full basement, the structure still requires effective protection against water ingress to ensure it remains dry and habitable—fully compliant with 𝗕𝗦 𝟴𝟭𝟬𝟮:𝟮𝟬𝟮𝟮 standards for below-ground waterproofing.

💧 𝗗𝗿𝗮𝗶𝗻𝗮𝗴𝗲 𝗦𝘁𝗿𝗮𝘁𝗲𝗴𝘆 – Gravity-Fed System:
As part of our design, we offered the option of a sump and pump system to manage any potential water ingress. However, the client opted for a gravity-fed drainage solution, which is a passive system that relies on natural fall to direct water away from the structure.

This approach involves:
✅ 𝗗𝗿𝗮𝗶𝗻𝗮𝗴𝗲 𝗰𝗵𝗮𝗻𝗻𝗲𝗹𝘀 integrated at the base of the cavity membrane system.
✅ 𝗣𝗶𝗽𝗲𝘄𝗼𝗿𝗸 𝗰𝗮𝘀𝘁 𝗶𝗻𝘁𝗼 𝘁𝗵𝗲 𝘀𝗹𝗮𝗯 designed with sufficient fall to ensure continuous flow.
✅ 𝗔 𝗻𝗼𝗻-𝗿𝗲𝘁𝘂𝗿𝗻 𝘃𝗮𝗹𝘃𝗲 fitted to prevent any risk of backflow from the external surface water system.

Gravity-fed systems are highly effective where site levels allow, offering a low-maintenance, energy-free solution for managing groundwater ingress.
We’re proud to support projects that combine modern construction with heritage sensitivity—delivering long-term protection and peace of mind.

🔹Cambridge House Walkthrough Video

🎥 Take a behind-the-scenes look at our installation work on the prestigious Cambridge House renovation project!

This video captures just a glimpse of the scale and complexity involved in transforming this iconic London landmark into a luxury 5-star hotel. With multiple phases and intricate detailing, it’s a project that demands precision, expertise, and collaboration—and we’re incredibly proud to be part of it.

From heritage preservation to cutting-edge waterproofing solutions, our team has been working closely with contractors and consultants to ensure the highest standards are met at every stage.

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