The brick wall above my apartment is blackened, what is it and is it possible to clean it?

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The brick wall above my apartment is blackened, what is it?

It is caused by water leaking from that drainpipe. It is some form of mould that thrive in damp conditions.

And is it possible to clean it?

Yes, a stiff-bristled brush and hard effort will make a big difference.

You can probably experiment with various chemicals, such as diluted bleach, to kill the mould.

If you do not repair the drainpipe, the problem will return in some months time, perhaps after winter or seasonal rain.

You can buy sealants that are intended for use on brick which prevent water penetration and which might help prevent this. They will alter the appearance of the brick though. This only works if the water is coming from the outside, not if the pipe with the leak is internal to the brickwork.

  • I've had great success using a chlorine-based (sodium hypochlorite 4.2%) anti-mould cleaner. Wear gloves and goggles, spray it on and let the chemicals do their work. No hard work required. – Sanchises Jan 21 at 10:28
  • +1 Used to work at a waterpark. Chlorine/bleach diluted with water works wonders on mould. Scrub with a stiff brush. – element11 Jan 21 at 14:32

It’s localized. That is to say, it’s only at the corner of the balcony and only extends down to the lower floor.

Moisture is causing the problem, but it’s not clear where the moisture is entering the wall. It could be coming from: 1) bad mortar joints, 2) drainpipe, 3) cracked brick cap at balcony wall, 4) crack around pipe

  1. If you look closely at the mortar joints, you’ll see cracks and gaps in the mortar. I doubt this is the cause of the leak, because the entire balcony wall (and pillar below) has the same bad mortar.

  2. If the pipe is a drain line it could be leaking in the wall. However, it’s odd that it stops at the upper floor line, unless there is a concrete slab that extends out to the edge of the balcony, thus stopping the leak from extending down the wall (column).

  3. it seems more likely that the construction at the corner is different than the rest of the balcony wall. Perhaps the corner was constructed differently and now is cracking and allowing moisture to enter. I’d check the top balcony wall cap and see if cracks are occurring along that portion of the wall cap.

  4. I doubt if it’s JUST leaking around the pipe. Otherwise it wouldn’t be so uniform throughout the corner.

The column and adjacent walls look like they could be “solid” brick construction and the area where the mold (discoloration) could be a veneer brick wall. If it’s veneer, water could easily get behind the moisture and be drawn out by high temperature (especially where you live) causing the black mold.

I agree with another response, you must find where the moisture is entering and fix it or it will return in a short time (one rainy season).

Adding water to clean the mold could cause additional water penetration into the wall. Fix and seal the wall before cleaning.

  • If you look at the "clean" wall below the blackened section in the second picture it looks like someone has blasted that bit with a powerwasher already to clean it. – Mauro Jan 21 at 14:19

I would wear a mask and buy a cheap power washer.

  • I'm not sure I'd use a power washer on a building I didn't own. If something happened to the brick, the liability here might be rather large to repair it. – Machavity Jan 21 at 14:46
  • Power washer is not strong enough to damage the bricks. It looks like half the wall was already power washed – C Fella Jan 21 at 17:27
  • Depends on the condition of the wall. I've seen some walls I'd never power wash, lest you remove some of the wall. Again, there's liability to consider before you go this route – Machavity Jan 21 at 17:29

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