Structure and support

Primary Structural Frames and Load-Bearing Wall Systems

A primary structure is a continuous route for load, running from the roof down through floors and walls to the foundations. The systems gathered here are the genuine alternatives for that route: load-bearing masonry, platform and post-and-beam timber, mass timber panels, cold-formed and hot-rolled steel, concrete frames and precast panels, insulating formwork, structural panels and volumetric modules. Each carries the same loads by a different arrangement of interacting parts.

The lateral stability system belongs here too, because a frame that carries vertical load still needs bracing, diaphragms or cores to resist wind and stay square. What is not here is the foundation the load path ends at, the floor decks and roof coverings carried within it, or any wall read as an envelope layer order — each of those is a separate family. Member sizes, connections and stability design belong to a structural engineer.

16 system entries · educational assemblies reference · how a system performs always depends on the whole building and qualified professional design

Scope

What this category covers

Where the boundary of this part of the encyclopedia sits, including what it deliberately leaves to qualified professionals.

Complete vertical load paths in masonry, timber, steel and concrete
Panelised, off-site and volumetric primary structures and structural panel systems
The lateral stability system that braces a frame and the secondary carcass it carries
Not covered: member sizing, span capability, connection design or lateral load calculation

All entries

Every frames & load-bearing walls entry

The complete set for this category. Frequently referenced entries come first — a starting point, not a ranking.

How the parts relate

Timber Platform Frame →A light timber structure raised storey by storey, where each completed floor becomes the platform for the walls above and sheathed stud panels do the bracing.

Steel Frame →A skeleton of steel columns and beams whose connections define its behaviour, stabilised by bracing, cores or rigid joints and completed by the floors that tie it together.

Load-Bearing Masonry →A structure in which the walls themselves carry floor and roof load down to the foundations, held in line by the floors and returning walls that meet them.

Post and Beam Frame →A skeletal frame of substantial timber posts and beams held square by braces and worked joints, with the enclosing walls built around or between it rather than carrying load.

Mass Timber Structure →A structure of large engineered solid timber panels used as walls, floors and roof plates, where stability lives in the connections and openings are cut before delivery.

Cold-Formed Steel Frame →A structure of thin steel sections made up into stud walls, joists and trusses, usually panelised off site and stiffened by sheathing or by discrete bracing members.

Concrete Frame →A cast-in-place frame of concrete columns, floor plates, walls and cores made continuous by reinforcement running through every junction, so the structure behaves as one element.

Precast Panel Structure →A structure of factory-made concrete wall and floor units carrying the building, in which continuity, robustness and weather resistance are all delivered at the joints between units.

Insulating Formwork Structure →A wall structure in which stacked hollow insulating units, held apart by internal ties, are filled with concrete and then left permanently in place as insulation on both faces.

Structural Insulated Panels →A structure of factory-bonded panels whose facings and insulating core act compositely, so each panel carries load and insulates at once, with splines and plates forming the joints.

Volumetric Modular →A structure made from complete units built and fitted out off site, each self-supporting when lifted, then stacked and connected so that paired walls and floors meet at every module face.

Portal Frame →A structure of repeated rigid frames in which stiff haunched joints hold columns and rafters together, tied along the building by purlins, side rails and bracing planes.

Lateral Stability →The arrangement that resists horizontal action on a building: floor and roof plates collect it, connections deliver it into bracing, walls or cores, and those carry it to the ground.

Mezzanine Structure →A self-supporting platform inserted within an existing tall space, carried either on its own columns and beams taken to their own supports or on connections made into the structure already there.

Roof Carcass →The structural framework giving a pitched roof its shape and carrying it down to the walls beneath, formed either from factory-made trussed rafters or from members cut and framed in place.

Stair Structure →The structure carrying a stair between two levels: the flight and its supports, the landings it starts, turns and finishes at, and the trimmed opening it passes through — not the guarding on it.

Elsewhere on Build Design Hub

Planning guidance for this subject

This encyclopedia explains how these assemblies are organised. These sections help with choosing between them and preparing for the conversation.

Build method discussion preparation →Preparing to discuss how a building will actually be built.Load path conversation preparation →Questions to prepare before a load path conversation.Frame construction questions →Preparation for a discussion about framed construction.

Materials Library

What these assemblies are built from

A systems entry explains how an assembly is organised. These materials sections describe the substances themselves — what they are, how they behave and what governs their use.

Masonry & Blocks →Reference entries for unit masonry — clay and concrete bricks, blockwork, mortars, and the ties, lintels and accessories that hold masonry construction together.Timber & Wood →Reference entries for solid timber and wood-based panels and engineered products — from structural softwood and plywood to cross-laminated timber, OSB, MDF and veneers.Metals →Reference entries for the metals used in building — structural and light-gauge steel, galvanised and stainless steel, aluminium, copper, zinc, lead and reinforcement.

Building Systems Encyclopedia

Reference entries for building assemblies — how each is organised, what role every component plays, how the parts interact and which junctions matter.

Browse all building systems →

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