My barn is probably 40+ years old and I've noticed the roof is starting to sag pretty badly in the middle section. I'm worried it might cave in during heavy snow or a storm. What should I look for to assess how urgent this is, and is this something I can tackle myself or do I need a contractor?
Have you checked whether the sagging is symmetric across the roof or concentrated in one spot? That matters a lot because uneven sag usually points to a specific structural failure (rotted beam, shifted post, failed tie rod) rather than general age-related settling, and it's way easier to fix a localized problem than to re-support an entire roof. Get someone out there to poke around the underside with a moisture meter and look for soft wood or visible cracks in the main beams - that'll tell you if you're dealing with rot or just deflection, and whether you're on a timeline of weeks or years.
This isn't necessarily a collapse-in-waiting situation - lots of older barns sag a bit and hold up fine for decades. That said, you definitely need to get a structural inspector or contractor out there to evaluate it properly, because they can tell you if it's just cosmetic settling or if there's actual rot, failing beams, or load issues that need urgent work.
Before you call anyone in, walk the interior on a clear day and look for light coming through cracks in the roof boards or between rafters - that's a red flag that things are actually separating. Also check the attic or loft for water stains, soft spots in beams, or signs of rot, since a barn roof doesn't sag evenly unless something's actively failing underneath.
If you're noticing active movement - like new cracks in the interior walls, doors that won't close straight, or gaps widening between boards - that's when you stop DIY-ing and call someone immediately, because those signal the structure is actively failing under load. For a slow, gradual sag that's been there a while with no new damage signs, you've got more time to get a proper assessment, but this really does need a pro's eyes since roof collapse involves liability and safety nobody should gamble on.
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