Paint problem

Check for dampness on your side and ask whether there are any pipes, leaks, or damp issues on your neighbour’s side opposite that area. Once the source is identified and fixed, scrape back the affected area, allow it to dry thoroughly, seal it with a stain-blocking/salt-resistant primer, then repaint. Simply repainting or replastering the spot is unlikely to be a permanent solution.

Try using stain blocker on the area

This is almost certainly efflorescence — a common issue where soluble salts from the wall materials (plaster, brick, mortar, etc.) dissolve in moisture and migrate to the surface. As the water evaporates, it leaves behind a fine white/chalky powder. Brush off the powder. Wipe the area with a 50/50 white vinegar + water solution (or a dedicated efflorescence remover). Let it dry fully. If the powder returns but no black/green mold smell/stains appear, it's salts, not biological growth. Vinegar helps dissolve salts.

In this case we would need to use what it’s called stain block you apply two coat of that and leave 30 minutes dry time in between and lastly you apply the emulsion

Buy a can of stainbloc and spray the area a few times then apply emulsion to finish.
Alternatively apply oil based undercoat to the area waiting until dry then apply emulsion to finish.

It sounds like moisture or contamination is coming through that section of wall, causing the paint to fail and turn powdery. The most likely causes are damp, salts from the plaster/masonry, or an old contaminant beneath the paint. The area should be checked for damp first, then sealed with a stain-blocking or anti-efflorescence primer before repainting.

Brush down the wall or scrub with warm water, ensure the wall is fully dry and no moisture or dampness is effecting the area, apply a bonding primer allow to dry and fresh coat with paint

I would strip the area back to plaster and prime it with a damp.seal or pva then fill and send then prim and 2 coats of paint

Its damp

That persistent powder sounds like efflorescence — a white, chalky deposit caused by moisture migrating through the wall and bringing salts to the surface. It’s common on shared or exterior walls, especially masonry or plaster ones, and fits your description: the paint looks fine for a few days, then turns powdery again even after sanding, priming, and repainting.

Here’s how to tackle it effectively:

Why it’s happening
Moisture intrusion: Water vapor from your neighbour’s side or from the ground moves through the wall, dissolving salts in the plaster or brick. When it evaporates, those salts crystallize on the surface — forming that fine powder.

Persistent substrate contamination: Even if you repaint, the salts keep migrating unless the moisture source is stopped.

Possible contributing factors: Poor waterproofing, high humidity in the kitchen, or an unsealed masonry joint between flats.

What you can do
Confirm it’s efflorescence:

Rub the powder with a damp cloth — if it dissolves, it’s salt (efflorescence). If it stays fuzzy or slimy, it’s mold.

Dry and clean thoroughly:

Brush off all powder.

Wipe with a 1:1 mix of white vinegar and water to neutralize salts.

Let it dry completely (use a fan or dehumidifier for a few days).

Seal the surface:

Apply a masonry sealer or damp?proof primer (look for “anti?efflorescence” or “moisture?blocking” products).

These create a barrier to stop salts migrating through.

Repaint with breathable paint:

Use a mineral?based or micro?porous paint (like silicate or limewash) rather than standard acrylic — it allows trapped moisture to escape without lifting the paint.

Address the moisture source:

Check for leaks, poor exterior sealing, or condensation on the neighbour’s side.

If possible, ask your neighbour or building management to inspect that shared wall for dampness.

If it keeps returning
You may need a professional damp assessment — sometimes the issue is hidden (e.g., a leaking pipe or capillary rise from below). A moisture meter reading will confirm if the wall is still wet inside.

If there is water penetration from the neighbour's side, that can cause a problem.

If it is not water penetration it might be something to do with the plaster itself - the plaster may have been contaminated by being mixed with something that is causing it to flake.

My suggestion is to hack off the area of plaster affected and redo it with sand and cement before you paint over it again.

Try applying a shellac based primer underneath such as Zinnser B.I.N 123 which will prevent any trouble surfaces being able to emerge through.

It sounds like you are dealing with a classic case of efflorescence caused by localized damp. This isn't just a "bad patch" of wall; it is a chemical reaction occurring because moisture is traveling through the masonry, dissolving minerals (salts) along the way, and depositing them on your wall surface as the water evaporates.

Wire brush or sand back the area to remove all loose powder and failed plaster.

Check with your neighbors to find out if they have the same issues as the problem could be within the adjoining cavity wall there is a water ingress problem.

The reason for this is because there is damp is coming through slowly and it is forming the paint into powder overtime glad to answer your question

Brush/scrape all loose powder off.
Let the area dry fully.
Seal it with a salt-blocking sealer (e.g. Zinsser B-I-N or Gardz).
Once dry, repaint.

Scrape and sand the area until you reach firm, stable plaster or drywall.
If there is still powdery surface underneath, it must be removed; otherwise the problem will return.

the powdery paint problem is usually caused by moisture seeping through the wall, potentially from the neighbor's side, maybe priming the wall with sbr could help before redecorating.

: Do not repaint until the moisture source is fixed. Check with your neighbor for any leaks or damp issues on their side of that specific wall
Use a stiff-bristled brush to remove the powder when the wall is dry. Do not wash it with water, as this can reintroduce moisture and bring more salts to the surface.

The cause of the paint not adhering to the wall is likely to be moisture in the wall
If this is rising damp from moisture coming up from the ground then usually the damp proofing to fix this is quite a major job
Rising damp is know not to rise further than six feet vertically. Rising damp is known as capillary action. If the damp is higher than six feet the cause is likely to be from water ingress from above eg. a leaking roof
If the cause cannot be addressed you could try to use a stain blocking primer on the wall before applying emulsion. I would recommend the red Zinsser primer which has shellac in the ingredients which has great moisture blocking properties, this is likely to work and is a leading product for this issue people often experience

What you’re describing is classic efflorescence / salt contamination, usually caused by moisture coming through the wall. The key clues are:
• Fine white powder forming after a few days
• Paint looks fine at first, then “disappears”
• Plastering over it only delays the problem
• It’s an external/party wall (neighbour on the other side)
• Keeps coming back no matter how well you prep

Paint and plaster are not the root problem here — they’re just getting sacrificed.

?

What’s actually happening (in simple terms)

Moisture is travelling through the wall from the other side (or from below), bringing salts with it.
When the moisture evaporates on your side, the salts crystallise ? powder ? paint loses adhesion.

That’s why:
• You can paint it ??
• It looks fine for days ??
• Then powder appears ?
• Brushing it off makes it look bare again ?

It's damp in some form,

Needs to be taken back and sealed in some form best way is zinsser block in most cases

What you're describing is almost certainly efflorescence caused by moisture coming through
that section of wall.

The fine white "powder" is salts being drawn to the surface by moisture in masonry or plaster.
when it dries, the salts are left behined and the paint loses adhesion, which is why it looks like it was never painted. Re-painting or skimming only hides it temporarily because the moisture is still there, so it keeps coming back.

It sounds like there’s damp in that area of the wall you need to rub that area down and apply a stain block to that area leave to dry and paint the whole wall again .

The best thing to do is remove the existing paint, brush all of the dusty area down, sugar soap the area, prime it with a suitable zinsser stabilising primer and then repaint

What you’re describing is almost certainly moisture-related salt contamination, not a paint problem. The key clues are:

Fine white powder forming after days

Paint film apparently disappearing

Replastering only delaying the problem

External/shared wall (neighbour on the other side)

This behaviour is classic efflorescence or salts being drawn to the surface by moisture.

The problem isn’t the paint — it’s moisture drawing salts to the surface (efflorescence), which forms a fine powder and breaks down any paint or plaster. Simply repainting or re-plastering won’t work. Dry-brush off the powder, then seal the area with a proper stabilising/salt-blocking sealer (e.g. Zinsser Gardz), follow with a stain-blocking primer, and repaint. If it keeps returning, there’s active damp in the wall (possibly from the neighbour’s side) that must be fixed for a permanent solution.

Brush off the powder and rinse off the area then let it dry completely. After that apply high quality alkali-resistant primer. After that use kitchen or bathroom paint as it is mold resistant. Also you must identify the source of dampness and fix it

What you’re describing is almost certainly **salt contamination caused by moisture** coming through that section of the wall. The fine white powder that reappears and makes it look like you never painted is typical of **efflorescence or hygroscopic salts**. Painting or skimming over it won’t solve it, which is why it keeps coming back even after plastering.

Because it’s a **party wall**, the moisture source is often slow and hidden rather than an obvious leak. It could be residual damp in the masonry, salts from old plaster, or moisture migrating from next door. Kitchens also add humidity, which activates salts even when the wall feels dry.

### Why it keeps happening

* Moisture moves through the wall and brings salts to the surface
* The water evaporates, leaving a fine powder
* Paint and plaster break down and release again
* Skimming just traps it temporarily

### What *will* work

You need to **isolate the salts**, not just cover them.

**Step-by-step fix (most reliable method):**

1. **Scrape and brush back** the affected area to bare, sound material
2. **Dry the wall thoroughly** – use good ventilation or a dehumidifier for a few days
3. Apply a **salt-stabilising / isolating sealer**, such as:

* Zinsser **Gardz** (very effective for this exact issue)
* Or Zinsser **BIN** (shellac-based, excellent at blocking salts)
4. Once fully dry, apply a **moisture-tolerant primer** (e.g. Bullseye 123 if BIN wasn’t used)
5. Repaint with your finish coat

If the surface needs levelling, do it **after the sealer**, not before.

Important

* Do **not** use standard PVA – it can make salt problems worse
* Do **not** replaster unless salts are sealed first
* If the powder returns even after sealing, there may be an **active damp source** that needs investigating (guttering, external pointing, neighbour’s plumbing, etc.)

I would sand and paint with a stabiliser then paint once dry this is a common problem could be salt or minerals in the plaster coming through a good stabiliser is going to make this area non powdery by making it no pourous and you'll be able to oaint it without any further problem

From what you’ve described, it sounds like that small section of wall has an underlying issue that’s stopping any paint from bonding properly. This usually happens when there’s either some old contamination in the plaster, a cold or slightly damp patch on the party wall, or salts pushing through the surface. That’s why the paint looks fine for a few days and then turns back to powder.

The best way to fix it is to remove the loose paint, clean the area, and seal it with a specialist primer such as Zinsser BIN, which will block any residue coming through. If damp is involved, a damp-seal product may be needed instead. Once sealed, the area can be repainted and it should hold properly.

It'll need to be cleaned, sanded and treated with Zinsser Gardz. Allow to dry for 24 hrs before face filling, sealing and painting.

1 Check for Leaks: Ask your neighbor if they have a sink/radiator leak on the other side of that wall. If the wall stays wet, paint will never stick.
2 Clean Dry: Do not wash it. Scrape and dry-brush the powder off. Vacuum the dust.
3 Seal It: Buy Zinsser B-I-N Primer (shellac-based). Apply 2 coats over the patch. This blocks the salts.
4 Paint: Apply your normal topcoat.

Call damp surveyor or knock back the brick work, seal it using ‘ zinsser - guardz’ replaster it

Hi there,

It sounds like you're dealing with a really frustrating issue! Given that the problem area is isolated and keeps returning with a fine powder, it suggests that there might be something underlying the wall that’s causing the paint to not properly adhere.

Here are a few potential causes and steps you could take:

1. Moisture Issues

Since this area is near your neighbor's side, there could be some moisture seeping through the wall, even if you're not seeing obvious signs of damp. The powder could be efflorescence, which is salt deposits left when moisture comes through the wall. This could explain why the paint is not sticking, even after sanding and cleaning.

What to do:

Check for any signs of damp on the wall, especially during rainy weather or after using water in the kitchen.

Use a damp meter (available at hardware stores) to check the wall for moisture. If moisture is detected, you may need to address the source (e.g., plumbing issues, condensation, or external wall problems) before repainting.

Apply a moisture barrier or use a specialized primer for damp walls before repainting.

2. Surface Preparation

If there’s been any lingering issue with the wall's preparation or cleaning (like residual grease, oil, or dust), that could affect adhesion. Even though you've already sanded and cleaned, sometimes specific areas need a bit more attention, especially if there are different materials or textures in the wall.

What to do:

Ensure that you’ve fully wiped the area down with a degreaser or cleaning solution, especially if the kitchen is prone to grease buildup.

Try using a bonding primer (designed to help paint adhere to challenging surfaces) before applying the final coat.

3. Neighbor's Wall Impact

Since this wall is shared with your neighbor, there could be an issue on their side (like rising damp, leaking pipes, or condensation) that’s affecting your wall. Even if it’s not visible on their side, moisture could be seeping through.

What to do:

If you’re comfortable, consider having a conversation with your neighbor to see if they’ve noticed any issues on their side of the wall, like condensation or damp spots. If they are, that could be contributing to your problem.

4. Plastering Issue

If you plastered over the problem and it only lasted a bit longer, it could mean the surface underneath is still not stable enough for paint to adhere to, even with the plaster applied.

What to do:

If the wall feels powdery after plastering, it might need to be re-skimmed or sealed with a special bonding agent to create a stronger surface for painting.

5. Different Paint or Finish

Sometimes, if the area is exposed to higher humidity (even subtle kitchen humidity), it could be affecting how the paint sets. Certain types of paint, especially matte or low-sheen finishes, are more prone to powdering over time in humid conditions.

What to do:

Consider using a different type of paint (such as a satin or semi-gloss finish) that's more resistant to moisture or marks in kitchens. This could help prevent the powdering issue.

In Conclusion:

You might want to start by testing for moisture on the wall. If you do find moisture, addressing that will be the first step before continuing with repairs. Once you’ve resolved the underlying issue, consider using a bonding primer and a moisture-resistant paint to give you the best chance at fixing the area for good.

Hopefully, this helps you get it sorted! If the problem persists, it might be worth getting a professional in to check for any hidden moisture or issues on your neighbor’s side of the wall.

It sounds like that small area might be affected by moisture coming through the wall — possibly from your neighbour’s side or from a hidden source of damp. When paint or plaster keeps turning to powder like that, it usually means the surface isn’t fully dry inside, even if it looks fine on top. The best way to fix it is to scrape back the affected patch completely, let it dry out fully (you can even use a fan or dehumidifier), then apply a stain block or damp-proof primer before repainting. If the issue keeps coming back, it’s worth checking for a minor leak or condensation problem on the other side of the wall.

remove everything back to a clean, dry surface, neutralise salts, seal with a proper damp-proof primer, then repaint — and make sure the source of moisture is addressed if it keeps coming back.

Potentially the surface underneath I.e the plaster could be a problem when paintier initially or there could be moisture in the plaster. The best way to deal with this is possibly to paint this user zinsser shellac paint. This paint will create a surface which should remove this problem

If the paint is on brick, render, or concrete, the white, powdery substance is likely efflorescence — salts coming out of the wall through moisture.
Cause: Moisture in the wall pushes salts to the surface, which dry and form a powder.
Remove the powder with a stiff dry brush (don’t wash with water — it can worsen it).
Find and stop the source of moisture (leaking gutter, poor damp proofing, etc).

Once dry, seal with a masonry stabilising primer before repainting.

you’ve done all the right prep steps, so the fact that this one small patch keeps “rejecting” paint and turning powdery means there’s probably something wrong beneath the surface, not the paint itself. From your description — powder reappearing, paint not bonding, plaster not holding — the most probable causes are: Persistent moisture coming through the wall (from your neighbour’s side, plumbing, or condensation).
• Even slight damp can migrate through plaster and push paint off as a chalky powder.
• This would explain why it takes days to appear again after painting. Efflorescence (salts coming through the wall).
• If moisture is moving through masonry, it can carry salts that crystallize on the surface, forming a white powder that looks like chalk dust.
• Painting over efflorescence never works long-term — it’ll keep reappearing. Contaminated or unstable substrate.
• If at some point that patch was treated with an incompatible product (oil, old damp-seal, adhesive, or even cooking grease that soaked in), it can stop anything from bonding properly. Step 1: Strip it back
• Scrape back all loose material until you reach sound plaster or masonry.
• If it’s plastered but soft, remove that section back to brick/block.
• Let it dry completely (can take days).

Step 2: Neutralize efflorescence or salts (if present)
• Brush the area with a stiff nylon brush and warm water to remove salts.
• Let dry fully.
• Avoid detergents — they can worsen it. Step 3: Seal the wall appropriately
Depending on what you found:
• If moisture is coming through:
Use a breathable damp-seal primer (e.g. Zinsser Watertite, Dryzone Damp-Resistant Primer) that allows some vapour movement but blocks salts.
Do not use PVA or standard sealer — it’ll trap moisture and make things worse.
• If the wall is dry and stable:
Use a stabilising solution for chalky surfaces (like Leyland Trade Stabilising Solution). Step 4: Replaster (if needed)
• Use a cement-based or waterproof plaster repair mortar (not regular gypsum) if the wall tends to get damp.
• Let it cure fully.

Step 5: Repaint
• Apply a quality breathable emulsion (avoid vinyl silk/glossy finishes).
• Two thin coats after full drying.

The appearance of a fine powder that brushes off, especially after a couple of days or a week, strongly suggests one of two common issues related to moisture and masonry, most likely salt efflorescence. To address this, I will first investigate the source by using a moisture meter to check for dampness, inspecting the exterior of the property, and checking the gutters for blockages or leaks. You would need to talk to your neighbours politely to explain the issue and ask if they have had any plumbing issues, persistent leaks, or other similar problems on their side of the wall. It is essential that I do not repaint until the moisture issue is resolved. Instead, I will scrape and clean the area, treat the salts with a chemical neutraliser, and properly prepare the wall before finally painting with the correct specialist damp-proof primer and topcoat to ensure a lasting repair.

In cases like these if possible and the neighbour would allow it to be checked out on the other side of the wall it may be caused by damp coming through the wall or even a chemical reaction

There will be some kind of moisture coming through for any number of reasons, one thing i would do is to re sand and clean the area then apply a correct primer leave to dry and then apply the top coat.

high-quality stain-blocking primer
mould and mildew resistant.

It sounds like that small patch of wall is affected by moisture or efflorescence (salts coming through the wall). Even though you painted it properly, moisture from inside the wall or from your neighbour’s side is pushing salts to the surface. That’s why the paint turns to powder after a few days — it’s not a paint problem, it’s a wall problem.

Here’s what to do:

1. Test for damp: Tape a piece of clear plastic tightly over the area for 48 hours.

If moisture forms underneath, the wall is damp inside.

If it forms on top, it’s surface condensation.

2. Scrape back to bare plaster or brick. Brush away all powder and loose paint.

3. Wash with a 50/50 mix of white vinegar and water to neutralise any salts. Let it dry completely.

4. Seal with an alkali-resisting or damp-blocking primer such as Zinsser Gardz, Zinsser B-I-N, or Dulux Trade Alkali Resisting Primer.

5. Repaint normally once dry.

If the problem comes back, it means there’s still moisture entering from the other side (for example, a radiator, pipe, or damp patch in your neighbour’s wall), and that needs to be fixed before the paint will last.

Because the wall backs onto your neighbour’s property, penetrating damp is the top suspect. Even a very slight, invisible amount of moisture from their side a leaking pipe, high humidity, or condensation can push salts and moisture through your wall. This causes efflorescence — the powdery residue salt crystals you’re seeing. Paint can’t adhere properly over this, so it keeps failing.

That’s a frustrating problem — and given what you’ve described, it sounds like you’ve run into a localized underlying wall issue, not just a paint adhesion failure. The fact that:

The rest of the wall is fine,

You’ve prepped, undercoated, and painted correctly,

And the paint turns to powder again and again in the same small spot,

… strongly suggests there’s a moisture or chemical contamination issue in that section of wall.

???? Paint Powdering Problem – Diagnosis & Fix
Issue: A small wall section (50cm × 15cm) repeatedly sheds fine powder, despite proper sanding, undercoating, and painting.
Symptoms: Paint appears fine for days, then turns chalky/powdery and wipes off easily.
Likely Cause:
• Persistent moisture from the neighbouring wall (possibly rising damp or trapped humidity)
• Contaminated or unstable substrate — old plaster, salts, or previous paint layers breaking down
• Efflorescence — salts migrating through the wall due to moisture, causing powdering

???? Recommended Fix
Step 1: Moisture Check
• Use a moisture meter or tape a plastic sheet to the wall for 24–48 hrs to check for condensation or damp
Step 2: Treat the Wall
• If damp is present: apply a damp-proof membrane paint (e.g., Zinsser Watertite or Dulux Trade DPM)
• If dry: seal with alkali-resistant primer or stabilising solution to lock down powdery surface
Step 3: Refinish
• Re-plaster if needed, then mist coat and repaint with breathable emulsion

Sounds to me if could be a damp issue, best way to find out is to masking tape a clear piece of plastic around the area affected and leave for 24/48 hours and see what happens.

Moisture = damp
Condensation = room humidity

The issue you're experiencing with the powdery substance on your kitchen wall is likely due to one of the following factors :
• Moisture Trapped Beneath the Surface: Moisture can be seeping from the neighboring wall or from within the wall itself, causing the paint to degrade and form a powdery substance.
• Surface Contamination: Dirt, oil, or grease might be present on the wall surface, preventing the paint from adhering properly.
• Poor Paint Adhesion: The paint may not be bonding well to the wall surface, leading to a weak and powdery finish.
• Efflorescence: Salts in the wall might be migrating to the surface, causing a powdery deposit.

Given your situation, here are some potential solutions:

• Clean the Area: Use a mixture of water and a mild detergent to clean the wall, and then rinse it thoroughly. Let it dry completely before repainting.
• Apply a Primer: Use a primer specifically designed to combat efflorescence or moisture issues. This can help seal the surface and prevent further damage.
• Use a Different Paint: Switch to a paint that's more suitable for areas prone to moisture or efflorescence. Look for paints with properties like water-resistance or anti-fungal agents.
• Seal the Wall: Apply a clear sealant to protect the wall from moisture and reduce the risk of further damage.
• Consult a Professional: If the issue persists, consider consulting a professional painter or a builder to assess the situation and provide a more detailed solution.

In your case, since the wall is shared with a neighbor, it's possible that the issue is related to moisture or structural problems that may require attention from both parties. You may want to discuss the issue with your neighbor to determine if they've experienced any similar problem

Wash down with sugar soap, allow to dry then put on wall sealer, allow to dry then apply paint 2 to 3 coats allowing time to dry in between coats.