Why is the paint completely peeling off the plaster?

It's likely due to not being appropriately prepped with a suitable primer, @SensibleHill. If the plaster is nice and smooth, you'll be good to go with Dulux PRECISION Sealer Binder White. It's an oil-based product specifically designed for sealing bare plaster. Standard water-based primers can delaminate like this due to the powdery surface and are better suited to paper-backed plaster.

Although the sealer is oil-based, it's suitable for all Dulux topcoats, so you'll be fine going over it with standard water-based Dulux Wash and Wear.

Since you appear to be on a roll, I recommend removing the remaining paint in the room and sorting out all the walls. That way, you don't have to worry about the other walls or remove their paint in the future.

Please let me know if you have any questions.

Mitchell

Thanks so much @MitchellMc - that’s what I suspected but I couldn’t find a clear answer online for a brick, rendered and plastered wall context. I’ll get that oil based primer onto the walls, pronto!

There’s one spot that is softer than the rest - it feels damp, and doesn’t have the same kind of coating. Backs onto the shower where there’s been water damage. I’m assuming the plaster hasn’t been sealed - or, water damage might have brendan repaired and that wasn’t sealed. Should I do anything to that area first before priming?

Thanks for all of your help!

Damp plaster would indicate there's an active water leak @SensibleHill. If this leak were some time ago, one would assume that the plaster should have had adequate time to dry out.

There's not much you can do from the room side to solve moisture in the wall without addressing the moisture source. You could attempt to dry it out with a room heater and then wait to see if the dampness returns. However, you really need to track down where the moisture is coming from. Now, depending on how far along you are with the bathroom remodel, this might involve some exploratory work on the other side of the wall. Ultimately you'll need to access the wall cavity to determine what's going on. If you're still planning on relocating the shower, I'd suggest doing that work on the bathroom side, but if not, you can cut into the wall on the room side. It will likely either be leaking pipework or a failed waterproofing membrane.

If it were me, I'd dry the area and paint it just to complete the room. Next, I'd remove tiles in the bathroom, cut the wall open, search for an active leak, and resolve it. Or, wait until you begin remodelling and get the plumber to check for the leak source whilst they're capping off the old water pipes to the shower. Worst case, the water returns to the wall and blows the paint off in that area, and you'll need to re-paint again. If you weren't moving the shower, I'd say open the wall in the room; otherwise, you'll destroy the shower's waterproofing membrane in the exploratory process.

Mitchell

Thank you! We are getting the plumbers in within the next few weeks, so will flag this with them.

Hi Mitchell,

I've had a similar problem. I put undercoat on plastered patches covering fine cracks in my walls (1960s flat). The undercoat paint began peeling as I painted. I had to wash the paint off the walls - about 15 buckets of water for 3 small areas!

1 Do I need oil-based Dulux Precision Surface Prep Sealer Binder? Or can you recommend a water-based product ?

2 How long should I wait for the washed plaster to dry before applying the Sealing product ?

3 There's still fine smears of paint on the plaster, will that be ok? I had to stop washing as the plaster was coming off.

4 Does it matter if I apply a paint brush to apply it, then roller for the undercoat and top coats?

5 How long do I wait for Sealer to dry before applying Dulux Ultra Air Interior Primer? 1 or 2 coats of Interior Primer?

Thanks for your further help Mitchell.

Liv

Welcome to the Bunnings Workshop community @LivMitch. It's sensational to have you join us, and many thanks for your question about painting plaster.

Do you have a bare plaster (no paper coating) wall? When you say the undercoat peeled off, was this an old undercoat over the bare plaster or a new one you'd just painted? I see you've removed the paint, but have you removed all the undercoat that was peeling?

1) Typically with minor repairs, you'd just use a water-based undercoat like Dulux 1Step Prep Primer, Sealer & Undercoat 1L. If it was a whole wall like in @SensibleHill's situation, it's best to use a sealer/binder. After a couple of coats of undercoat, you'll be fine to apply your topcoat wall paint.

2) It sounds like you've fully saturated the plaster so I'd recommend giving it the best part of a week to dry out. You could run a heater in the room periodically to speed up the process. Make sure it doesn't get too warm though as you'll risk cracking the plaster. Keep it under 30 degrees celsius.

3) Fine smears of paint on the plaster should be fine and is certainly better than washing away the actual plaster.

4) The sealer binder can be applied with a brush or roller, and then you can apply your topcoat with either as well. However, I'd suggest using a roller for both as it will eliminate brush strokes.

Dulux PRECISION Sealer Binder White can be top-coated in 24 hours, also depending on weather conditions. If it's cold or humid, it's best to wait 48 hours. To clarify, you only need two products, the Dulux PRECISION Sealer Binder White and your wall paint topcoat. There is no additional undercoat required, the sealer binder is your undercoat. If you are using the Dulux Ultra Air Interior Primer over the sealer binder for its Low Voc qualities, the same 24-hour rule applies.

Please let me know if you have any questions.

Mitchell

Hi Mitchell

Thanks for your quick reply! The photos are SensibleHill's walls, not mine 😉

My walls have been previously painted 17 years ago (and before that, it's a 1960s block of flats). Sorry but I don't know what you mean by a bare plaster (no paper coating) wall...

The plasterer applied plaster to long, fine cracks in these walls – patches are approx 1m square each.

I sugar soaped the walls.

I applied an undercoat paint to the 3-weeks dry plaster patched areas (undercoat paint was 17 yrs old but recently used with no issues on window frames).

As I applied the undercoat paint, it was not sticking to the wall properly, peeling off as I painted (using a roller).

So I washed off as much undercoat as I could (water and a Chux super wipe).

Now I will:

* exchange the oil-based Dulux Precision for the Dulux 1 Step, Prep Primer

* apply 2 coats of this

* 1 top coat of Dulux Ultra Air Interior Low Sheen Walls

Thank you! So grateful for your expertise and quick help.

🙂

Liv Mitchell

Hi @LivMitch,

I apologise, as I might have assumed more similarities with @SensibleHill's project than there were. Their paint and undercoat completely delaminated from the bare plaster. It's an older style of plaster that doesn't have a paper coating like newer plasterboards.

If the undercoat you're using wouldn't stick to the cleaned wall then it sounds like some type of incompatibility. The wall's not painted in gloss paint, is it? I'd suggest doing a test section with the Dulux 1 Step. Apply it to a small area and wait for it to dry completely. Place Painter's Tape over it and wait five minutes. Tear the tape back off and see if it removes any of the undercoat. If it removes the undercoat, then you might have to look at sanding the wall for better adhesion.

Mitchell

Hi Mitchell

My bad, it's me not understanding apples vs oranges re Sensible Hill. The undercoat I used wouldn't stick to the plaster. It was a normal undercoat not a 'primer' or 'sealer' or 'binder'. It was also 17 years old (perhaps the age of the undercoat was the issue)

I will do a test patch of Dulux 1 Step 1 as you suggest and masking tape.

My concern is that the Dulux 1 Step product says it is for use on:

"Apply it confidently to most surfaces including brick, masonry, paper-faced plasterboard, timber, MDF, render, concrete, cement sheet, galvanised iron, Zincalume steel, PVC and previously painted surfaces."

1. Does new plaster, on top of a previously painted wall, fall into any of those categories?

Doesn't sound like it. That's why I brought Dulux Precision which says:

" For porous surfaces including plaster, cement sheet ...."

2. Is Dulux 1 Step definitely what I need?

Thanks Mitchell.

Hi @LivMitch,

For smaller repairs, Dulux 1Step Prep Primer, Sealer & Undercoat 1 is fine to use, I've confirmed this with Dulux technical team. You mentioned above that "The plasterer applied plaster to long, fine cracks in these walls – patches are approx 1m square each.". If just the cracks were filled then the 1 Step is appropriate. However, if the repaired section is a large one-metre squared area, then the sealer binder should be used. You might like to post some pictures of the repair, so I can see what you are working with. Let me know if you need assistance uploading an image.

Mitchell

OK Mitchell I'll get some photos now. Hang on a sec or six! Thank you for your patience and effort 🙂

washed off undercoat. plaster drying.connector room 2bathroom 1bathroom 2bathroom 3 - darker area bigger than 1 sq mspare 1 - see darker area left sidespare 2 - slightly darker above door to right 0.5 sq m spare 3 spare 3 spare 4 spare 4spare 5 most of lower part and 2 x 1 sq m patches either side of window

IS THERE ANY CHANCE you are able to resolve this today? Tomorrow is my only day to prep before the big Easter paint job.

Photos hard to take (poor phone cam and lighting conditions). Hope these suffice.

The cracks were fine cracks, however the plasterer chose to cover a large area around them.

Sometimes the wall was bumpy and gouged, from a bad 'bog' repair previously.

One spare room crack was fine (you couldn't fit a knife blade into it) but long, three-quarters the length of the wall and up toward ceiling, for example.

EricL

Hi @LivMitch

Thanks for posting those photos of the wall repairs. Just to be on the safe side, I suggest using the Dulux PRECISION Sealer Binder White on those repaired areas. You can clearly see that the plasterer did a thorough repair job as they covered the entire wall and not just the cracks.

I'm sure @MitchellMc will chime in if he has more information to add.

If you need further assistance, please let us know.

Eric

Hi Eric,

Thanks for getting back to me. I'll go the oil-based Sealer Binder. Was trying to avoid the sickening smell.

1 or two coats Eric?

Thank you both for your help.

Liv

There's no requirement to do two coats @SensibleHill. You just need to apply enough for complete coverage. You might get away with one thick coat.

Mitchell

Great! Thanks Mitchell. Have a good one.

Hello there,

My ceilings are previously painted. I've sugar soaped them. No flaking paint.

1) Do I need to undercoat them?

2) Can I use Dulux Ultra Air Primer as an undercoat?

3) Or do I just do 2 coats of Dulux Ultra Air Ceiling Whitex?

Thanks so much again.

(PS: Mitchell/Eric - the Precision Sealer Binder has been applied and looks good - thanks for your advice)

It's great to hear the Precision Sealer Binder worked well @LivMitch!

The general rule for ceilings or walls is that if the paint is in good condition and you've given the surface a clean with sugar soap (remember to wipe the wall down with fresh water after), then you can apply your topcoat paint straight over it without priming. Given those prerequisites are fulfilled, you can just do 2 coats of Dulux Ultra Air Ceiling Whitex.

Please let me know if you have further questions.

Mitchell

Well that's fantastic news Mitchell, thanks!

This one is quite flat. No more paint to peel away after a light sand I think.You can see that it's ready to peel away more. It's puckered away from the surface.Good Morning,

I'm repainting my ceiling with Dulux Ultra Air Ceiling White (no Primer).

I have 3 small patches of the existing paint peeling off as I paint. It looks like there is one coat beneath the top coat and then board (plaster board?).

I wiped it over with a damp cloth and let it dry first. I have painted 95% of the ceiling with no problem. Just this one corner with 3 patches.

1) What should I do to fix this?

2) Can I get away with sanding it back with 120 fine grade paper, and if so, do I use Sealer Binder on the board then Dulux Ceiling White?

3) Also, my 2 rollers are still damp and I need to get painting. Is it OK to use them if they're still damp? You can't wring any droplets from them...

Thanks for your help Team!

Liv

Hi @LivMitch,

If the edges of the peeling paint are well bound and difficult to continue peeling away, then your method sounds like it will work. Sand the edges of the peeled areas to remove their proudness and blend in a smooth transition. 120-grit might be a little coarse but should work in a pinch. 180-grit is likely in the right ballpark. You can then use the Sealer Binder. Paint it over the board and off onto the existing paint by around 50mm. Once dry, you'll be able to paint with your ceiling white.

Please let me know if you have any questions.

Mitchell

Terrific, thanks so much Mitchell.

Hi @MitchellMc & @EricL

our renovation has moved slowly since we can only work weekends, and we’re finally looking to move in - sans bathroom 🤯 it’s all part of the adventure!

with the walls above, they’re all patched with rapid fix and I’ve skim coated the white set with Gyprock Top Coat (Gold) which has produced amazing results. I just wanted to check if there was anything else I should do before applying the Dulux 3-in-1 prep / sealer / primer?

Thanks so much!

here’s some photos of the before, and then the freshly plastered front entryway

walls

Hi @SensibleHill,

It's great to hear that things have been progressing. For larger areas of plaster filler, it's recommended to go with the Dulux Precision Sealer Binder, which is an oil-based version, instead of the water-based version, which is better suited to smaller repairs.

Apart from making sure that everything is flat and well-sanded, there's nothing else I can think of.

Mitchell