65 year old rock lathe ceiling issue

jeffp

New Member
Hi,

Sorry if this is long but the details seem pertinent....i grew up in the house and now work on fixing issues.
1 story ranch house, ceilings are rock-lathe with a scratch coat and skim coat finish...65 years old with a sand half moon swirl finish. 2 issues have presented.

1. whole ceiling painted in 2018 by me with behr ceiling paint….august of 2023 i noticed a paint blister. Of course i had to poke at it...it was brittle with what seemed to be the textured skim coat underneath. It was small so i sanded it...but noted that there were some other smaller blisters and more material easily came off to the skim coat, tapping with my finger allows me to hear where its loose. i primed with kilz oil based and put latex behr ceiling paint over it. It reacted and sort of fizzled like a chemical reaction hours to a few days after and would just slough off....and i now noted yellow discoloration and some craze lines that were discolored away from the blisters. The discoloration could be washed away but would return???
This went on with trying various things like a water based primer as well till october 23 when i heavily scraped sanded and washed it down with i think a vinegar rinse...still in teh skim coat...let it dry and then rolled on bin primer..then the behr ceiling paint and it has been solid since...1 year this month.
I looked for water intrusion...found a single nail pop on the roof in the vicinity of this area and repaired that...Im 6-5 230# so getting in out of the crawl space is not easy at all so i wanted to avoid that. Other than this small maybe 2ft long 1 foot wide space I scraped...no other issue, no other sign of water. No pipes or ductwork in the crawl space either...just insulation..old rock wool in some areas with pink fiberglass on top and blown in cellulose...good soffits with a good ridge vent.

2. This is the big issue now...not sure if its tied to the other....Im outside buffalo NY..we have a massive storm in January 24...5 feet of snow a clear day then another 4 feet. the ceiling (other side of the same room) formed a perfectly linear crack from 1 side to the other. i went out shoveled the roof and the crack closed to a fine line. inspecting further...another brittle paint blister with textured skim coat underneath again subtle discoloring as in what i described in #1. I called a plaster guy in our area...he was very detailed, explained the ceiling type and that he wouldn’t do a true repair as it would be gross overkill and explained how to seal it and paint over it. so i lightly caulked the crack, scraped away the blisters, put in some daptex to fill to level, primed with bin and painted....it was fine from March until sept/oct...I last looked at the ceiling in July it was fine and then last week saw the crack had returned, the daptex crumbled, more brittle blisters in areas i had painted and more surface discoloration...
-Wiping the discoloration with bleach eliminated it
-Checked the roof again...nothing but roof..no corners, angles, pipes or junctions..just shingles all intact
-I said screw it and just started hard scraping of whatever was loose, i took off the areas down to the grey scratch coat..what you see in the pics. This included all areas that were discolored /blistered/cracked
It easily came off with nothing more than a flat head screw driver.
-The scratch coat is rock hard, no dripping no moisture etc that I can tell...i scraped back to skim material that is really attached and not coming off.

I have a few more spots to chip out but all the surrounding area is clean, hard, no cracks no discoloration....this was just around the linear crack and where i had primed and painted......

My plan is to use plaster weld, diamond veneer plaster mix with plasteres sand, sponge float after it starts to set to try and get the swirls close. Then I have to figure out how to prime as there seems to many opinions on how and when to prime how to prime and paint…I have kilz oil, Zinsser 123 and bin……ill probably just let it sit and cure for an extended time.

Any ideas on why the blisters, the discoloration (which I know would be water but there isn’t any unless it happened along time ago and worked its way thorough)…could it be its age?

Thanks for any ideas thoughts and again sorry for the long post….jeff
 

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I think the US and the UK do things slightly differently. Why not just pull the whole mithersome thing down, insulate and plasterboard?

Is there any chance the old ceiling could have asbestos? Just a thought
 
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