Insulating 32 Top-Floor Flats in Mitcham
A 1940s solid-wall block of flats in Mitcham, South London, comprises 82 flats in total, including 32 on the top floor directly beneath a large flat roof.
The landlord approached Pyramid Eco to address significant heat loss through the roof, cold ceilings in top-floor flats, and emerging condensation issues, while also renewing an ageing roof covering. The aim was to improve resident comfort and secure a long-term waterproof solution through the Great British Insulation Scheme.
Project Snapshot:
Location: Mitcham, South London
Property Type: 1940s solid-wall block of flats
Client: Private landlord/freeholder
Purpose: Reduce heat loss, improve comfort, and renew the ageing flat roof
Solution: Flat roof insulation with ventilation upgrades
System: Fatra single-ply membrane system with 150mm insulation
Funding: Great British Insulation Scheme (GBIS)
The Challenge
The flats relied mainly on electric panel heaters, making heat expensive to generate and quick to escape through the uninsulated roof. In several top-floor flats, condensation and minor mould had already begun to appear, caused by the cold roof surface above.
As the project was funded through GBIS, only a single insulation measure could be installed. Unlike ECO4, this was not a full whole-house retrofit, so the focus had to be precise. That meant the focus had to be precise. The roof needed to be properly insulated, and the ventilation upgraded to match.
Why Pyramid Eco?
The landlord chose Pyramid Eco because this type of project requires more than just a roofing contractor. It requires the right accreditations, access to funding, manufacturer approval, and a team experienced in retrofit delivery.
Access to Funding
Not every contractor can access GBIS funding. Pyramid Eco manages the entire process, from eligibility checks to submission and compliance, making it straightforward for landlords and freeholders.
Manufacturer-Led Approach
Rather than creating a system from off-the-shelf materials, we work directly with approved manufacturers. This ensures proper design, structural checks, and long-term guarantees.
Qualified and Accredited Teams
All installers are NVQ-qualified and trained in the specific systems they install. Projects are overseen by a Retrofit Coordinator and subject to independent inspections.
Long-Term Protection
By combining proper specification, trained installers, and manufacturer oversight, the landlord secured a 20-year manufacturer-backed guarantee on the roof.
Our Approach: A Properly Designed Roofing System
Working alongside the Retrofit Coordinator and the funding provider, Pyramid Eco specified a complete flat roof insulation system in partnership with the manufacturer from the outset.
Rather than assembling materials independently, we selected a fully approved Fatra single-ply membrane system. The existing roof deck was assessed, 150mm insulation boards were installed, and a new waterproof membrane was fitted above to create a durable, watertight finish.
System: Fatra single-ply membrane system
Insulation Thickness: 150mm rigid insulation boards
Coverage: Over 1,400m² of flat roof area
Funding Route: Great British Insulation Scheme
The manufacturer carried out wind load calculations and pull-out testing before work began, followed by mid-installation and post-installation inspections. This ensured the system was suitable for the building and installed exactly to specification. By involving the manufacturer from the start, the landlord secured a compliant, fully assessed system backed by a 20-year guarantee.
Related: Why Pyramid Eco Is Moving from Torch-on Felt to Single-Ply Membrane for Flat Roof Insulation
Overcoming Key Challenges
This was not a small residential roof. At over 1,400 square metres, the project required careful phasing and constant monitoring to deliver the work safely and correctly.
1. Winter Installation
The works took place during the colder months, when temperature and humidity conditions must be closely monitored. Roofing systems cannot be installed in heavy rain or freezing conditions without risking long-term performance. The roof was completed in sections, with pauses between phases to wait for suitable weather.
2. Working at Scale
At over 1,400 square metres, the roof required careful sequencing and site control. Each section had to be insulated and sealed before progressing, ensuring the building remained protected at all times.
3. Managing Moisture and Existing Issues
Some top-floor flats had condensation and minor mould. Affected areas were treated before insulation was installed, and ventilation was upgraded to reduce the risk of recurrence.
4. Protecting Long-Term Performance
The manufacturer carried out wind load calculations and inspections during and after installation. This ensured the system was correctly specified and installed, securing a 20-year guarantee for the landlord.
Results and Benefits
Pyramid Eco’s flat roof insulation upgrade has improved thermal performance across all 32 top-floor flats. While the heating system remained electric, the reduction in heat loss through the roof has made a noticeable difference to comfort and condensation risk.
Key Outcomes:
- Improved comfort for top-floor residents, with warmer ceilings and reduced heat escape
- Lower risk of condensation and mould due to upgraded insulation and ventilation
- A fully renewed, watertight roof covering
- Long-term cost protection for the landlord
- Reduced capital expenditure through GBIS funding support.
All Work Is Protected by Robust Guarantees and Full Compliance:
- 20-year manufacturer-backed guarantee on the roofing system
- Retrofit Coordinator oversight throughout the project
- Mid and post-installation inspections by the manufacturer
- Compliance with current building regulations and funding requirements.
Client Satisfaction
The landlord was extremely pleased with the outcome. The roof was approaching the end of its life, and combining renewal with insulation through GBIS funding delivered substantial value.
They appreciated Pyramid Eco’s clear guidance on funding eligibility, the manufacturer-led approach to system design, and the careful management of works during challenging winter conditions. The completed roof improves resident comfort, reduces condensation risk, and provides long-term protection backed by a 20-year guarantee.
Planning Flat Roof Insulation for a Block of Flats?
Improve comfort, reduce heat loss, and secure long-term protection with expert support from Pyramid Eco. We deliver manufacturer-approved flat roof insulation systems, installed by qualified teams and backed by robust guarantees.
From funding applications to final sign-off, we manage the process clearly and professionally, giving you confidence at every stage.
