MGP10 Rafter and Roof Member Spans

Updated 2026-02-03 · MGP10 Span Tables

Roofs bring a few extra variables to the party. Alongside spacing and span type, roof members care about how much roof they carry, how heavy that roof is, and what the wind is doing. Get those three right and MGP10 roof spans make sense.

Roof load width

Roof load width (RLW) is the roof equivalent of floor load width: how much roof area a member must carry down to its supports. As with floors, a larger RLW means more load and therefore a shorter allowable span for a given size. Roof tables are built around RLW, so it must be established correctly — see wind classification and load width.

Roof mass: sheet vs tile

Wind matters on a roof

Wind loads the roof — including uplift that tries to lift it off — so the wind classification (N1–N4, or C1–C4 in cyclonic regions) directly affects roof member spans and the tie-down design. Always read the column for your assessed wind class, not a guess.

Rafters, beams and the limits of MGP10

MGP10 commonly suits rafters and ceiling joists in ordinary domestic roofs. But ridge beams, hanging beams, strutting beams and other members that gather large areas or point loads can exceed what MGP10 handles in a sensible size. In those cases a higher grade, an engineered beam (LVL, glulam) or a specific engineering design is the right answer.

Don't forget the overhang

Roof tables often give both a maximum span and a maximum overhang (eaves). The overhang is governed too — a generous eave changes the demands on the member. Read both figures, not just the span.

Approaching the lookup

For an MGP10 roof member: establish RLW, identify roof mass (sheet or tile), confirm your wind class, set spacing and span type, then read the size that meets your span and overhang from the current table. The Span Spec Builder gathers RLW, roof mass and wind so your lookup is complete.

On the roof

Keep going

For openings and concentrated loads, read MGP10 lintels and beams, and make sure you are solid on deflection.

Frequently asked questions

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