The sag is likely swelling from long term humidity and requires replacement. You will never make it flat again. Sound's like tile has staples/nails on lips concealed by adjoining tile. It will take investigation to determine if tile is nailed to solid wood ceiling or glued on laths. Either one will likely require replacing sagging tile with new which will result in color difference. Not to rain on your parade before the band strick's up but beware if glue is black. Black glue from 50s often contain's asbestos.

Thanks for the note. I am considering using Plaster buttons, and spackling over the buttons. We are planning on putting moisture resistant drywall on top on the tiles in our bathroom. I have some tiles that I can pull off in the top of cabinets that were installed after the tiles were put in, and can find out if glue was used. It really looks like they were just stapled in place.

Why don't you just pull them all off and go back to the original ceiling? You would get more bang for the buck by restoring the old ceiling than restoring the ceiling tiles.

It was common to put these on to reduce heating costs. It doesn't necessarily mean that the ceiling above is damaged. We had our ceiling tiles (only in sitting room and dining room) tested and pulled them down. It took us very little effort to restore the original ceiling and it looks so much better. Even added drywall over the original ceiling would be better than the tiles - IMO.

Good thought, we are doing that in our bathroom. While these aren't asbestos, the glue that was used be may contained in, so pulling them down is not going to happen.

I assume you have verified that they are glued to the ceiling? I've always seen this type of tile installed by stapling through the interlocking tabs (which are hidden after installation), and there was never any need to use any adhesive. In fact, I just removed some from the ceiling of my back porch, and they had held up in humid outside weather for 30-40 years with only staples.

Bruce

Can anyone suggest the best place to send in one of these to have it checked for asbestos? We are about to put the house on the market and realtor thinks it is asbestos tiles. If we sell to someone using FHA loan, it could be an issue.

Hi there, I only heard this today from the realtor. I was a bit skeptic. I never got confirmation on the glue. There are kits via Amazon that include testing, I found them earlier. Here's one. I'm in SE Georgia USA. (I'm probably a glutton for punishment!)

We use a lab from the EPA web site. We mailed in our sample and they emailed us with results in 2 days. It cost $20. So worth it.