[shelzmike]

In my 1943 home, we have ceiling heat that does actually still work and work well. The way the ceiling is constructed is quite strange. Starting from the framing above, it has 1/2" plywood, a layer of old school gypsum board, then the wires for the ceiling heat are coiled around, then (I think a brown coat), then a white coat with the texture in the pictures below. It is not popcorn ceiling of course. It is some sort of ridged, non-uniform, texture.

We cannot remove it all and leave it flat because the ceiling is all sorts of bumpy and wavy but this texture REALLY does a fantastic job of hiding the imperfections and it actually doesn't look bad as a whole.

The problem, though, is that due to the ceiling constantly expanding and contracting due to the ceiling heat, there are areas where the white plaster has fallen off in pieces. I need to try to patch those areas with new plaster and blend it in with the same texture, but can't figure out how it is done. I am thinking maybe I put a slightly thick layer of plaster on (about 1/4") and then use some sort of non-linting towel and use it to sort of pull the ridges out. Is that anywhere close to how to do this?

 

[Nealtw]

It looks a lot like the icing on a baked Alaska cake.

 

[ClarenceBauer]

From your description it is a USG Radiant Heat Cable system.
It make up would have been a base coat of USG Diamond Plaster with sand added than scratched, than a finish coat of USG Diamond finish NO sand troweled smooth.
The Texture was USG Simulated Accoustical QT texture Finish, which was spray applied. This product was labeled as Asbestos FREE? If doing a lot of work have it checked.
For repairs I would recommend the use of USG Diamond Finish for the areas where the smooth finish has failed also use a bonding agent on the repair area.
As for the texture finish the QT texture I don't believe is available any more.
Your spray texture looks like it was applied using a Plaster Pump? It is going to be very hard to match it.
Question how large of a repair is required?
Is the existing texture hard or soft?

 

[shelzmike]

It is hard. I mean, it you are painting and those ridges it your knuckles, you will bleed 🙂

What you are saying makes sense, mostly. Though I am torn on thinking it was sprayed though it absolutely could be.

And wow, the name that has been tip of the tongue all this time just hit me! It is stippling! That is the texture that the ceiling has.

It really doesn't look like a spray, looks more like it was pulled into ridges while still thick and wet.

 

[ClarenceBauer]

It is hard. I mean, it you are painting and those ridges it your knuckles, you will bleed 🙂

What you are saying makes sense, mostly. Though I am torn on thinking it was sprayed though it absolutely could be.

And wow, the name that has been tip of the tongue all this time just hit me! It is stippling! That is the texture that the ceiling has.

It really doesn't look like a spray, looks more like it was pulled into ridges while still thick and wet.

Yes it could have been applied than pulled with a trowel to make the stipples.
To match how large of an area do you need to match?
There is a way to match it but will take some time to make up the template.
You could also practice using joint compound on a sample board when you have it worked out you switch to the Diamond Finish product.

 

[shelzmike]

There actually isn't any pattern to it. It is all completely random in ridge spread, size, etc. I think this will make it easier to repair.

Most spots to repair are small. About maybe 6" x 4", a few cracks that run along a specific length that correspond to the panels. I do have one area that is bigger, maybe 2' x 3'. I think I can use a stipple brush and the right consistency plaster, or I can possibly even make it work with drywall mud for that matter. It all has to be repainted anyhow, it isn't as though the mud will get disturbed way up there, but I think I'd rather use plaster if I can get the consistency correct.

 

[ClarenceBauer]

Don't use Joint Compound of any kind as it will fail due to the heat.
Also the wrong topping will effect the heating.

 

[Old Thomas]

I thought it was an aerial view of Uranus.
Actually it looks like a stippled finish put on with a stippling brush. Diluted plaster or compound is rolled or lightly troweled on the ceiling then it is stamped with the stippling brush, leaving the little points. Sometimes the brush is dipped into the material and stamped on for repairs. The texture will match, just gotta figure out what to use for the goop.

 

[Sir MixAlot]

After the compound was applied by hand or roller, it looks to me like someone used a sponge to create that texture.

In this photo, I'm using a sponge to match knockdown texture on a small wall repair and this is what it looks like before it gets knocked down.

 

[shelzmike]

After the compound was applied by hand or roller, it looks to me like someone used a sponge to create that texture.

In this photo, I'm using a sponge to match knockdown texture on a small wall repair and this is what it looks like before it gets knocked down.

Yessir, that looks exactly like what I need to do. Are you using mud or plaster here? I'm going to have to use plaster, though admittedly, I haven't really worked with it that much before. I have plenty of plywood scraps I can practice on for sure.