Why the names overlap
In everyday project discussions, “space frame” and “space truss” are often used for similar-looking spatial roof systems. In structural analysis, a truss normally describes an idealisation in which members carry axial forces and joints are treated as pinned. A frame model may also include bending and joint stiffness. Naming alone cannot settle which model is appropriate.
The distinction matters when drawings, specifications and supplier proposals use different terminology. Ask for the system description and the modelling assumptions, not simply a label. Background on truss behaviour.
Compare assumptions, not marketing names
For a proposed roof, a productive comparison records the following questions side by side:
- How are connections represented in the analysis?
- Where are loads introduced, and are there intermediate loads on members?
- How are supports restrained, released or allowed to move?
- What provides stability during construction and in the completed structure?
- Which details connect the roof covering and secondary steel to the primary system?
A real connection has physical dimensions and stiffness. The chosen idealisation must be justified by the responsible designer; it is not established by an illustration on a website.
Two-dimensional and spatial systems
A plane truss principally lies in one plane. A spatial system has members arranged in three dimensions. A building may also use multiple plane trusses together with bracing and secondary framing. These arrangements can look similar from one camera angle while having different load paths and fabrication requirements.
When reviewing alternatives, request a plan, a section and a support diagram. This small set of drawings is more informative than a single perspective rendering.
Questions for a supplier comparison
Separate structural scope from commercial scope. One proposal may cover primary members and nodes only, while another includes secondary steel, protective coating, packing, erection assistance or roof cladding. A cost-per-area comparison without matching scope can be misleading.
Use the same project brief for each enquiry. Record exclusions, unresolved information and the process for approving changes. Do not assume that differently named systems are interchangeable or that components from two suppliers can be mixed.
What to take forward
The useful outcome of an early comparison is a clear description of the intended system, the interfaces to be resolved and the documents required for the next stage. A schematic illustration can support that conversation, but final member sizes, connection design and erection requirements need project-specific work.
Continue with bolt-ball connections or supports and bearings to examine two important interfaces in more detail.
References & further reading
Background resources; applicability and current editions must be checked for the project. Referenced organisations do not endorse this site.
