I want to repaint my ceiling, but I can’t quite tell what’s going on. Is there a layer of drywall? Plaster?
What should I do if I just want to repaint?
From the big chunk that is missing I would say plaster, but not the first time as it looks like there is another level under that one. In the 70’s my dad remodeled many Victorians in the SF north Bay Area of CA. Even featured in sunset magazine not sure of the year, we would strip the old woodlath and plaster to the studs and Sheetrock then heavy mud to look like old plaster. The tough ones were from the 30-40’s with expanded metal and mortar but these crack but never drop a section as your photo shows. Filling cracks will give some time but it will crack again unless not reenforced with mesh paper tape won’t last as well in my experience. Depending on the area I have found 3 types of studs from your era, Redwood , no rot and easy to rip and strip old plaster, Fir mid level nails pull out most of the time but break off close to the coast, not two bad, Oak framing , this is just about impossible to pull a old nail or drive a new one or screw without a pilot hole being drilled first. They each have pros and cons and depending on the zone the home was built can be great advantages at this age, if 2 layers there ways to fill the hole but cracks will come back from what I have seen unless structural and multi layer problems are repaired.