What is a single beam layer?
A single beam layer is a floor or ceiling structure consisting of one tier of parallel timber beams that span directly from one load-bearing wall to the other. It is the simplest and most commonly used form of timber beam floor, suitable for relatively modest spans.
Construction and layout
In a single beam layer, all beams run in the same direction and at the same level. Their beam ends rest directly in or on the load-bearing masonry walls. The typical centre-to-centre spacing ranges from 300 to 600 millimetres, depending on the beam dimensions and the expected loading.
A floor finish is applied on top of the beams — for example floorboards, plywood, or OSB panels. On the underside, a ceiling of plasterboard or timber lining boards can be fixed. The spaces between the beams provide room for thermal and acoustic insulation.
Span range and application
A single beam layer is suitable for spans of up to approximately 5 to 6 metres, depending on the beam cross-section and timber species. For larger spans, the required beam dimensions become impractically large, and a composite beam layer or alternative structural system is the better choice.
Typical applications include:
- Intermediate floors in residential buildings
- Attic floors
- Ground floors above a crawl space
- Floors in outbuildings and barns
Advantages
The single beam layer is straightforward to design, build, and calculate. Material use is efficient and the construction offers flexibility for layout changes. Openings for services and ducts can be formed relatively easily, provided structural rules are followed.
Limitations
For larger spans or heavier loads, the single beam layer reaches its limits. Vibration and deflection can become problematic if the beams are not adequately sized. In such cases, a composite beam layer with primary and secondary beams provides a more effective solution.
Related terms
- Beam layer
- Composite beam layer
- Beam floor construction
- Beam end
- Floor joist
- Centre-to-centre spacing
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