NON-PENETRATIVE STEEL SUB FRAMES
Designed, Supplied & Installed with Comprehensive Structural Reports
At 360 GSS, we specialise in non-penetrative steel sub frame systems designed to support balconies, roof terraces, decking and balustrades without fixing through the flat roof waterproofing.
Our systems are engineered to sit above the roof membrane, eliminating penetration points, preserving roof warranties, and mitigating thermal bridging by avoiding direct structural connections between internal and external elements. The result is a robust, compliant solution that protects both the building fabric and long-term energy performance.
WHY CHOOSE 360 GSS FOR NON-PENETRATIVE SUB FRAMES?
CUSTOM ENGINEERED SOLUTIONS
Every non-penetrative steel sub frame is designed specifically for the project in question. We account for roof construction, loading requirements, balcony depth and balustrade height to deliver a solution that is structurally sound and visually integrated.
Our frames are manufactured to tight tolerances, allowing seamless integration with decking systems and glass balustrades while maintaining compliance with UK building regulations.
PROTECTING YOUR ROOF & THERMAL ENVELOPE
By avoiding fixings through the roof membrane, our non-penetrative systems significantly reduce the risk of water ingress and protect existing waterproofing guarantees.
Crucially, this approach also mitigates thermal bridging. With no steel elements penetrating the insulation layer, heat loss is minimised, condensation risk is reduced, and the building’s thermal envelope remains intact. This is particularly important for modern warm roof constructions and energy-efficient buildings.
LOAD DISTRIBUTION, STABILITY & SAFETY
Our non-penetrative steel sub frames are designed to distribute loads evenly across the roof surface using engineered base plates, spreader systems and ballast where required.
This ensures the imposed loads from balconies, decking and glass balustrades are transferred safely without overstressing the roof structure below, while maintaining stability under wind and line-load conditions.
GLASS BALUSTRADE & DECKING INTEGRATION
Non-penetrative sub frames provide a secure foundation for frameless and framed glass balustrade systems. Base channels and posts can be fixed directly to the steel frame without compromising the roof membrane or insulation.
This allows clean detailing, uninterrupted views and full compliance with required barrier loadings.
READY FOR YOUR NON-PENETRATIVE STEEL SUB FRAME?
360 GSS offers a complete end-to-end service, covering design, structural calculations, fabrication and installation.
Every non-penetrative steel sub frame is supplied with full engineering support, ensuring compliance with building control while protecting waterproofing systems and minimising thermal bridging.
PREMIUM SERVICE & ALL WORK GUARANTEED
We manufacture bespoke non-penetrative steel sub frames using high-quality steel and corrosion-resistant finishes as standard.
All projects are backed by professional indemnity insurance, providing confidence that your installation is designed for long-term performance, structural integrity and thermal efficiency.
FREQUENTLY ASKED QUESTIONS
What is a non-penetrative steel sub frame?
A non-penetrative steel sub frame is a structural support system that sits on top of a flat roof without drilling or fixing through the waterproof membrane or insulation layers. It is used to support balconies, roof terraces, decking and glass balustrades while preserving the roof’s integrity.
How does a non-penetrative sub frame protect the roof?
By avoiding fixings through the roof covering, the waterproof membrane remains intact. This significantly reduces the risk of leaks, prevents damage to insulation layers, and helps retain existing roof warranties.
How does this system mitigate thermal bridging?
Because the steel frame does not pass through the insulation layer, there is no direct thermal connection between the interior structure and the external balcony or terrace. This helps reduce heat loss, lowers condensation risk, and maintains the building’s thermal envelope.
Are non-penetrative steel sub frames compliant with UK building regulations?
Yes. When correctly designed and engineered, non-penetrative steel sub frames are fully compliant with UK building regulations. All systems supplied by 360 GSS are supported by structural calculations and designed to meet loading and safety requirements.
Can a non-penetrative sub frame support glass balustrades?
Yes. These frames provide a strong and stable foundation for frameless and framed glass balustrade systems. Balustrade base channels or posts are fixed directly to the steel frame, not the roof membrane.
Are these frames suitable for all flat roof types?
Non-penetrative steel sub frames are suitable for most flat roof constructions, including warm roofs and inverted roofs. Each design is assessed individually to ensure compatibility with the roof build-up and load-bearing capacity.
How are loads managed without fixing into the roof?
Loads are spread evenly across the roof surface using engineered base plates, spreader systems and ballast where required. This ensures imposed loads from balconies, decking and balustrades are transferred safely without overstressing the structure below.
Is a non-penetrative sub frame suitable for retrofit projects?
Yes. Non-penetrative systems are particularly well suited to retrofit installations, where penetrating an existing roof would be disruptive or risk invalidating warranties. They allow balconies or roof terraces to be added with minimal impact on the existing building fabric.