Definition, structural design and fields of application
In many complex industrial and civil contexts, the architectural configuration of buildings or the nature of the heating system itself makes the use of conventional flue systems anchored to existing structures impractical. In these scenarios, the self-supporting chimney system — also referred to as a self-supporting flue duct or free-standing system — represents the standard technical solution. It is a system that independently provides its own structural stability, without relying on shafts, walls, or external supports, transferring loads directly to the ground or foundation through its supporting structure.
Self-supporting chimney systems: differences from conventional systems
A conventional flue system is designed to be housed within a masonry shaft or anchored at regular intervals to building structures — floors, beams, and load-bearing walls — which provide vertical and lateral support. The self-supporting chimney system reverses this concept: the duct and its supporting structure form a single, independent system capable of standing autonomously without external support, except at the base.
This structural feature has significant implications both in design and installation. From a design perspective, a self-supporting chimney system must be sized not only for thermal stresses generated by flue gases, but also for static and dynamic loads resulting from its own weight and wind action. From an installation perspective, it requires a properly sized base anchorage and, in many cases, a dedicated foundation.
The distinction from traditional supported systems is therefore not merely terminological: it defines a product category with specific technical and regulatory requirements, requiring integrated expertise in flue engineering and structural engineering.
Typical application contexts
The choice of a self-supporting flue duct is driven by the impossibility or impracticality of anchoring the system to building structures. Typical applications include:
- Medium and large industrial plants — heating plants, steam generators, industrial furnaces — located in open halls or outdoor areas without vertical anchoring structures
- Existing buildings undergoing renovation or change of use where creating a shaft would be invasive or architecturally incompatible
- External installations where the heat generator is located in a separate technical room and the duct must run outdoors before reaching its final height
- Contexts where urban or architectural constraints prevent modifications to façades or structures
- New construction projects where plant layout places heat generators away from vertical structures
- Replacement of old masonry chimneys with modern modular systems where the original shaft is no longer usable
In all these cases, a self-supporting chimney system allows the creation of a compliant flue system without major structural modifications, offering flexibility and cost efficiency.
Technical parameters to consider
The design of a self-supporting chimney system requires a multidisciplinary approach combining flue engineering and structural design.
The overall height is the most critical parameter: wind-induced bending moments increase with the square of the height, requiring greater structural rigidity or the use of guy wires and bracing systems.
Wind load must be calculated based on location, altitude, terrain roughness, and duct geometry.
Thermal expansion is critical: metal ducts expand significantly with temperature variations, requiring properly designed expansion joints.
Aerodynamic sizing of the inner duct must comply with EN 13384, considering flue gas flow, temperature, and draft requirements.
Installation and maintenance
The installation of a self-supporting chimney system differs from conventional systems due to its complexity.
The base anchorage must be designed to withstand structural and wind loads.
The assembly is carried out progressively from bottom to top using lifting equipment, ensuring alignment and stability.
Maintenance includes not only flue inspections but also structural checks: corrosion, anchorage integrity, expansion joints, and fastening systems.