Making sure the deck’s ready for underlayment - what’s your process?

I’ve found a couple of soft spots that way I’d never have noticed from above.

Yeah, crawling under there is a pain, but it’s wild how many issues you can spot from below - especially with older joists. I ended up using one of those cheap inspection mirrors and a flashlight to check the tightest spots. Not perfect, but better than trying to wedge myself in every time. Wish there was a robot for this stuff...

Inspection mirrors are a lifesaver, but I’ve started using my phone camera for tight spots - just snap a few pics or record a quick video under the deck and zoom in later. It’s not perfect, but it’s saved my back more than once. Have you ever tried gently tapping the joists with a screwdriver handle? Sometimes it’s the only way I catch those hidden soft patches before they get worse. Curious if anyone else relies on sound as much as sight when checking for trouble...

I get the appeal of using your phone for those awkward spots, but I’ve had mixed luck - sometimes the glare or shadows make it tough to see what’s really going on. I still trust my hands and a pry bar more than anything. Tapping joists is good, but I’ve found that sometimes rot doesn’t sound off until it’s already pretty far gone. I usually poke around with an awl or screwdriver tip, just to be sure. Sound helps, but I wouldn’t rely on it alone.

I usually poke around with an awl or screwdriver tip, just to be sure.

Same here - my phone’s just a flashlight half the time. I’ve found more rot with a cheap screwdriver than any fancy tool. Once poked right through a joist that looked fine from above... learned my lesson quick.

Had a deck job after a hailstorm where the homeowner swore everything was solid - looked fine, barely any staining. I started poking around with my trusty screwdriver and, sure enough, nearly put my foot through a “good” board. Sometimes I think rot’s got a sense of humor, hiding right where you least expect it. I’ve tried moisture meters, but honestly, nothing beats a sharp tool and a suspicious attitude. If it feels spongy, it’s coming out... even if it means more work.