White powdery wall mystery

[Andmakeitsnappy]

I have a decorating problem akin to one of those locked room mysteries and would be so happy if someone could come up with a solution.

My son’s bedroom is a small box room just big enough for a three-quarter size bed and fitted wardrobes. It has three outside walls, one with a double window, and a plasterboard partition wall housing the door and radiator. In terms of ventilation there is an airbrick on the window wall and a reasonable size gap under the door. Additionally, one of the windows is open most of the time.

The walls were painted in Homebase dark blue matt vinyl but after many years a white, powdery substance appeared on the surface. Although this washed off, it slowly returned.

Now for the odd bit. The powdery substance covered both the outside brick walls and the plasterboard wall but not behind a large framed poster on the outside wall.

A decorator recently sanded down the walls and applied two coats of professional Valspar paint, but once again the ‘powder’ has returned.

This leads me to think that the problem might be airborne. And yet it doesn’t affect the wardrobe surfaces, nor the carpet. Plus another wall in the loft painted with the

same Homebase paint is also unaffected.

Paint manufacturer’s helplines have failed to come up with a solution. Can you help?

 

[Wayners]

Learn: What Is Efflorescence?

Everdry Waterproofing of Wisconsin explains efflorescence, the white stuff on your walls. Learn what it is and how it affects your home.

www.everdrywisconsin.com

Efflorescence occurs when water moves through a porous material, dissolving the salts within. When the water reaches the surface and evaporates, it leaves those salts behind, creating a chalky, white deposit. Moisture and soluble salts must both be present for efflorescence to appear.

 

[michealangelo]

I have a decorating problem akin to one of those locked room mysteries and would be so happy if someone could come up with a solution.

My son’s bedroom is a small box room just big enough for a three-quarter size bed and fitted wardrobes. It has three outside walls, one with a double window, and a plasterboard partition wall housing the door and radiator. In terms of ventilation there is an airbrick on the window wall and a reasonable size gap under the door. Additionally, one of the windows is open most of the time.

The walls were painted in Homebase dark blue matt vinyl but after many years a white, powdery substance appeared on the surface. Although this washed off, it slowly returned.

Now for the odd bit. The powdery substance covered both the outside brick walls and the plasterboard wall but not behind a large framed poster on the outside wall.

A decorator recently sanded down the walls and applied two coats of professional Valspar paint, but once again the ‘powder’ has returned.

This leads me to think that the problem might be airborne. And yet it doesn’t affect the wardrobe surfaces, nor the carpet. Plus another wall in the loft painted with the

View attachment 377743same Homebase paint is also unaffected.

Paint manufacturer’s helplines have failed to come up with a solution. Can you help?

If this is efflorescence don't wash down the powder , that will just start the reaction again

If it's very bad dry brush it off

Then apply two coats of alkali resisting primer

Then if that seals it you should be able to emulsion it