Is it normal for spray foam to shrink and pull at the ceiling drywall?

That sounds like a classic case of delamination or shrinkage caused by an improper mix ratio during the initial spray. When closed-cell foam isn't mixed at the perfect 1:1 ratio of 'A' and 'B' sides, or if the ambient temperture was off during the application, the chemical reaction doesn't finish correctly. It can take months or even a full year for the internal stresses to build up enough that the foam starts to pull away from the substrate. The fact that your drywall is bowing upward is the biggest red flag. That foam has a massive amount of tensile strength once it cures. If it's shrinking, it’s not just opening a gap; it's literally acting like a winch, pulling on the baffles and the framing members. Since the foam is bonded to the rafters and the baffles are likely pinned near your ceiling joists, that inward tension is transferred directly to your finish materials. I'd be very skeptical of an installer saying they've never seen this. It’s a known failure mode in the industry called **dimensional instability**. You need to have that contractor come back out and take core samples. They shold be looking for a 'friable' texture—if the foam feels crunchy or looks like it has a charred, darker color in the center of the lift, it was sprayed too thick or too hot.

You can't just patch 2-inch gaps with a can of Great Stuff and call it a day. If the foam is still actively shrinking, it will just tear the patch apart. The failed sections relly need to be cut out and the manufacturer of the resin should be looped in to determine if the batch was bad or if the tech just botched the calibration on the proportioner. If they refuse to move, get a third-party inspector who specializes in building science to document the **uplift** on your ceiling before it cracks the drywall tape globally.

Oh wow, that sounds like a total nightmare but also kinda fascinating in a sci-fi way! I'm just getting started with my DIY renovations and I had no idea foam could actually be strong enough to warp drywall like a winch. That's wild! Do you think the same thing could happen with those DIY spray kits you buy at the big box stores, or is this just a pro-grade chemical issue? I was thinking about doing my crawlspace this weekend but now I'm nervous I'll accidentally pull my floorboards up!

I’ve seen this exact mess with Demilec Heatlok HFO when the tech tries to push a 4-inch lift in a single pass to save time. Those exothermic reactions are no joke. If your installer used a Graco Reactor E-30 and didn't have the heaters dialed in for the ambient dew point, you’re looking at serious dimensional instability. That 'winch' effect is likely pulling on your top plates, not just the drywall. Check the rafters for any splitting where the foam has the strongest grip. I'd bet my last dollar they didn't check the substrate moisture content before spraying. Was it raining the week of the install?

Update: Thanks for the input. I checked the foam and it definitely looks like they sprayed it in one thick pass instead of multiple layers. Someone mentioned that exothermic reaction, and some spots actually look charred inside the cracks. Is there any way to stabilize this without ripping out all the bowing drywall, or is the tension just going to keep building until something snaps?