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I own a new house and I want to know if it is necessary to paint the rafters of my roof. The roofer told me that I was not obliged to paint them. Thank you your answer.

The question suggests that you are talking about the part of rafters which remain visible on the underside of the roof. If so, you can paint them (with a microporous paint for wood) or stain them, to protect them from bad weather. You can also to protect the debor of under-roofing with some wood paneling or some PVC blades. This solution is aesthetic and it participates in theattic insulation. It also avoids the penetration of birds in the attic.
If it is non-visible chevrons, there is no point in painting them.

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