Roof construction, also called roof structure or roof framing, is the load-bearing framework of a roof that transfers the weight of the roof covering, insulation, wind loads, and any snow or maintenance loads down to the walls and foundations of a building.
Types of roof construction
There are two main categories of roof construction: pitched roofs and flat roofs. Pitched roofs use angled structural members and come in many forms, including gable roofs, hipped roofs, mansard roofs, and mono-pitch (lean-to) roofs. Flat roofs have a slight slope for drainage but appear level from the ground.
The structural system can be based on traditional cut rafters, factory-made roof trusses, or engineered timber beams. Cut rafter roofs are built on site from individual timbers and allow for open loft spaces. Prefabricated trusses are manufactured to precise specifications, delivered to site, and craned into position, offering speed and consistency. Steel and concrete roof structures are common in commercial and industrial buildings.
Key components
A typical timber roof construction includes rafters or top chords (the sloping members), ceiling joists or bottom chords (the horizontal members), purlins (horizontal beams supporting the rafters mid-span), a ridge board or ridge beam at the apex, and struts or braces for additional stability. Each component is sized by a structural engineer based on span, loads, and material grade.
Application
Roof construction is designed during the structural engineering phase of a building project. The design must account for dead loads (self-weight of materials), live loads (maintenance access), environmental loads (wind and snow), and any additional loads from solar panels, green roofs, or roof terraces.
For renovations such as loft conversions, the existing roof construction often needs reinforcement or partial rebuilding to accommodate new floor loads, dormers, or altered roof geometry. A structural survey is essential before any modifications are made.
Related terms
- Roof sheathing
- Rafter
- Roof truss
- Roof covering
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