How to Measure Curved Verandah Rafters
Quick answer
Record the verandah projection, the height difference between the wall plate and front beam, and the rafter section depth. Identify the roofing product and curve type; for an existing roof, an original rafter is the most accurate pattern.
Ordering curved verandah rafters starts with three pieces of information: the rafter style, its overall length and the external radius of the curve. A tracing or an old rafter can provide additional confidence when the existing roof is unusual.
The four common period profiles are bullnose, concave, convex and Olde Gothic. They create very different roof lines, so identify the shape before taking detailed measurements.
Measure the overall rafter length
Record the required finished length in millimetres. Note where the rafter begins and ends, including any projection beyond the beam. If an original rafter is still in place, photograph both ends and the points where it meets the building and verandah beam.
Do not rely on one deteriorated component alone. Compare several rafters where possible because rot, movement and previous repairs can change the apparent size.
Use the external radius
The radius describes the curve. The brochure specifies the external measurement: the outside edge of the timber curve. This matters because measuring the inside edge produces a different figure.
The roofing and timber have to follow compatible curves. If rolled steel is being ordered separately, make sure the rafter maker and roofing supplier are using the same reference radius.
Record the timber section
Measure the height and thickness of the existing timber section. Standard profiles are only a starting point; older houses often contain work that was made for that building. Record the dressed finished size rather than guessing from a nominal timber description.
Hips and valleys need separate information
A straight curved rafter is not the same as a hip or valley. If the roof turns a corner, mark the roof plan and identify every hip and valley. Photographs taken from the ground, roof level and underneath the framing can prevent a left-right or inside-out misunderstanding.
A useful rafter enquiry includes
- Profile: bullnose, concave, convex, Olde Gothic or a custom match
- Quantity required
- Overall finished length in millimetres
- External radius in millimetres
- Finished timber section
- Hip or valley angles, where applicable
- Photographs and a tracing or sample when available
For restoration work, the safest instruction is often “match this surviving rafter” supported by dimensions. The workshop can then compare the sample with its existing patterns and determine whether a standard or custom curve is appropriate.
Common measuring mistakes
The most common errors are measuring the inside radius instead of the external radius, recording a sloping chord instead of the finished curved length, and assuming every rafter on an old verandah is identical. Another mistake is ordering rafters before the roofing curve has been agreed. Timber and steel suppliers need to work from compatible information.
If the existing rafter is too damaged to measure, create a full-size tracing from a better example or provide a drawing from the project designer. You can compare the standard shapes on the verandah rafter range, then send the full set of measurements through the job enquiry form.
Check the drawing before manufacture
For a custom curve, ask for the agreed style, radius, section and overall length to be written together. A small labelled sketch is easier to verify than a list of numbers with no reference edges. Keep that approved information with the order so the roofer, builder and workshop are all reading the same dimensions.