California?

Likely, unless the tenant or someone was walking around in the attic, these are stress cracks. Potentially caused by small earthquakes, the house settling, or even big truck traffic on the street. Not generally a big deal unless they are getting larger (by larger I am saying anything more than hairline cracks) or more are appearing.

PLASTER CEILINGS:

If your house is older than about 1955, it likely has PLASTER and not drywall on the ceiling and walls. If it is plaster, immediately Check the cracks, especially in the 3x4 foot area and see if these cracks interconnect. Check to see if the area has ANY flex to it where, if you push up on it, it moves a little (any movement is bad, 1/4 inch or more is worse). You can use a broom to push up on it and watch carefully. If it moves, the plaster has released from the backing and is getting ready to fall (this is for PLASTER only). If so, clear the area and tell tenants NOT to walk or do anything under it as it can let loose and injure or kill someone. If it's loose, move things away and clear the room and put tarps down. Then pull the loose area down (a garden hoe works good for this). Once all the loose area is down, get some drywall, cut strips about 4 inches wide and attach them on the joists in the area where the hole is to level things up. Then drywall over the entire ceiling in that room and finish it and then paint. You don't want more areas in that room coming loose.

Check your yard if you have had a lot of rain in the past year or so and the downspouts don't take the water away from the foundation. Water near the foundation can cause walls to settle and create cracks.If the yard is ok, it's likely just settling over the years.

Now, if the ceilings are drywall:

To fix them, if you decide to, either caulk them and try to blend it together (this is hard to make it really match) or using all purpose drywall joint compound (mud), put the mud over the crack, then put drywall joint tape and smooth it out. After the mud dries, cover the tape with 2 more coats of mud, each coat wider than the first to blend it in and make the patch as invisible as possible. Let the mud dry between coats. When done, sand lightly to help blend it in and then reapply texture to match. There are many types of textures, so maybe ask someone who knows in your area or post some pictures here and I can look and tell you what type texture it is and how to duplicate it. After the texture is done and blended in, you'll need to prime and paint. Old paint will have faded over time, so plan on painting the entire ceiling area in the rooms where the cracks are located, likely 2 coats, one primer and one finish paint. Especially if smokers are or have been in the home. This is going to run several hundred dollars, even if you do it.

Material list: all purpose drywall joint compound, drywall tape, sandpaper (180-220 grit)

Tools: workbench or stepladder, tarps, 6,8 and 10 or 12 inch drywall trowels, drywall mud pan, something to apply texture, depending on what type texture it is (spray can, trowel, hopper , compressor (depending). Paint equipment- brushes, rollers, roller frame and paint pan, extension handle for roller.

Also, just for your info.

Plaster, drywall, drywall joint compound and popcorn ceiling texture from before about 1976 ALL contain asbestos in them. In those days, it was normal in many materials including floor tile, siding and more. If it is in this era, you need to be careful because Calif (and, really all states) have rules for dealing with it and serious penalties if you ignore the rules. (Like it or not) Tenants can be affected and often call lawyers and this can get very expensive. You might be cautious and call an asbestos abatement contractor to deal with this if the house is older than about 1978. This can get expensive. NEVER EVER say the word asbestos around a tenant.

Also: Many insurance companies do not cover anything related to asbestos. Don't say that word to them either. If the house is older than 1978, let us know and we can give more info.

RobertJ from Ca also likely has much experience in this area.

I agree with Richard. As a home inspector I had to "diagnose" drywall cracks all the time. There are two types of drywall (or plaster...for this topic I'm using the terms interchangeably although clearly they are very different products)....

1) drywall that's cracked

2) drywall that's GOING to crack

If it is plaster dig the cracks out and then fill them before you texture and paint.

If it is drywall it should not be cracked unless it is at the seams.

Cracks in the mud can be because the coating was applied incorrectly. Maybe it was just too thick. If it was a patch job and the mud was slopped in there it could crack.

Find out what you have, drywall mud, plaster, cracks at seams, stress cracks, etc. Then you will be able to get the problem resolved.

If it is cracking at the texture you might be chasing those cracks for a long time.