Orange Rust bleeding through Finished plaster from Backbox?

[ldogg]

Have 2 locations where orange rust marks are bleeding through from a light-switch back-box to the finished plaster through the paint.

I replaced one of the 'rusty' back-boxes, although the replacement is rusting again, where i possibly sanded the edges after filing around it?

There appeared to be a drop of water from the inside of one of the boxes, could this be condensation rather than water coming through the wall?

The wall in the first photo was taken back to brick where it had blown and rerendered/ plastered. There is always a line on the wall between new and existing in these winter months which wasnt present during summer, maybe think the whole wall should have been cut back now.

L

Untitled

• ldogg
• 23 Feb 2014
• 1

Untitled

• ldogg
• 23 Feb 2014
• 1

Untitled

• ldogg
• 23 Feb 2014
• 1

The house is not yet lived in so heating only only at a weekend.

Any ideas?

Thanks

 

[Micilin]

Dry a bit of wall. Tape a square of see through plastic or tin foil to it,sealing the edges. Leave for a few days. If moisture appears on the room side , it's condensation. On the wall side, damp.

You have an issue here.

What were the damp issues before?

 

[Flyboytim]

Condensation is very likely during October-March if heating is only on at weekends.

Intermittent central heating will allow the air to rise in temperature rapidly, and humidity from the air will condense on surfaces below the dew point, like the metal box in contact with the brickwork, in a wall that is predominantly covered with old dry plaster, with a patch that is rendered and skimmed with gypsum being colder, and slower to warm up than the original materials.

I think these boxes are made from Galvanised sheet steel, then punched out then folded into boxes, so there are lots of exposed steel surfaces even before they were installed, and there is also the earth connection (not green/yellow sleeved in the image!) that can have some electrolytic action on the box if there is not good bonding between all the service earths and ground in the property, on some supply systems.

Increase air movement and ventilation when the property is reoccupied, and do not blast the heating on full in all the rooms to get it comfortable quickly. Allow rooms to warm up gradually with thermostatic controls, and lower output temperatures for the radiator feed. If you have a programmer, turn the heating on in advance of arriving at the weekend.