Bearers and double bearers span?

[pete5]

In the situation of building a timber deck, I would like to know how the span length changes when you have a 'double bearer (two lengths laminated together)?

If a 140x45 MGP10 has a span (as a bearer) of 1400 (single or continuous), If I stuck two lengths of 140x45 together, how far could it span?

[MitchellMc]

Hi @pete5,

When laminating two 140x45 MGP10 bearers together to create a double bearer, the span capacity does increase, but not proportionally. While the load-carrying capacity effectively doubles, the span does not. This is because the ability of a beam to span distances depends on its stiffness and section properties, which don’t scale linearly with thickness. As a general rule, doubling the thickness of a bearer increases the span capacity by about 25-30%. So, if a single 140x45 MGP10 bearer has a span of 1400mm, laminating two together might allow for a span of approximately 1750mm to 1800mm. However, for precise measurements and compliance with building codes, it’s essential to consult span tables or a structural engineer. 

Please let me know if you have any questions.

Mitchell