Efflorescence ... ?

[Arfa Daily]

Driving around the village over the last few days, I have seen a huge amount of efflorescence on walls, that I don't ever remember seeing before. One wall, that must be a hundred feet long and 7 feet tall, seems to have so much white deposit on its surface, that at first I thought that vandals had 'treated' it to a paint job. This particular wall is 20+ years old, in pretty standard looking Golden Fleck type brick to match the houses. I think that it probably forms a retaining wall for at least part of its height, which I thought at first might give a bit of a clue as to what was going on, but the more I looked, the more walls I found that were suffering, many of which are just free standing boundary walls. As I pulled back up at home, I noticed that the low wall with pillars that my neighbour had built 3 years back, has become likewise afflicted. It looks almost as though someone has taken a brushful of whitewash to it.

So, has anyone else noticed this ? Anyone venture a suggestion as to what is different about this year that has started this happening ? I had thought that this effect only happened on new bricks, but apparently not ?

Arfa

[mail]

Pretty common and not just with new bricks

Chris

[Arfa Daily]

Oh yes. I've seen it many times, but primarily on new bricks, and am well aware of what it basically is. Just that I don't recall ever having seen it 'appear' suddenly, in the sorts of quantities that I am talking about, on old(er) walls. Hence why I asked if anyone else had seen it like this in their area.

Arfa

[damduck-egg]

Are these various walls alongside roads? just wondering if it could be Salt laid down in the cold snap a few weeks back that has been sprayed up onto the walls. I don't think there has been much rain recently to wash it off a lot surfaces.

G.harman

[john]

As a guess I'd be thinking that efflorescence on brickwork is normal. It's effects haven't been seen until recently as the acid rains effectively dissolved it. Clean up the power stations and all we are left with is efflorescence and sodding green mould and lichen growing on every external surface. Bring back the acid rain!.

[Arfa Daily]

Well, yes, these are walls close to roads, but a salt / gritting truck never came as much as 'close' to our village during all of the recent snow woes, so I am reluctant to believe that it is road-salt related.

Arfa

[Arfa Daily]

This is not just 'recent' - it is sudden. And the amounts are very significant. It literally looks as though someone has tried to whitewash these walls. I take your point about the acid rain, and the way it kept chemical surface blooms and botanical growths at bay, but in reality, we haven't really had rain at that level of acidity for some years now, so I don't think that this sudden appearance of efflorescense can be attributed to that. Puzzling. Has anyone else actually noticed any of the same in their area ?

Arfa

[Gib Bogle]

When you say "bricks", I presume you mean those coloured brick-shaped lumps of concrete. Those on our house produced quite a bloom when the weather cleared up after a long period of heavy rain.

[Arfa Daily]

Well, when I say "bricks", I mean "bricks" really. Sort of 'brick-shaped' baked lumps of clay with "LBC" stamped into the frogs. The sort of thing that a brick wall or brick house might be built of. Nothing to do with concrete, afaik ... ??

Arfa

[Gib Bogle]

OK, I stand corrected. In these parts (NZ) most so-called bricks are not fired clay these days. I haven't seen efflorescence from real bricks - clearly my experience is limited.

[The Natural Philosopher]

That's the sort of Euro spirit we need in these troubled times.

Stamp into the Frogs, I say.

[Arfa Daily]

Ah ... NZ ! Sorry if my previous reply sounded a bit pissy - it wasn't really intended to. Just a bit tongue in cheek really. Don't normally expect to get Kiwis on a UK group ! (I hope 'Kiwi' isn't seen as one of those 'racist' things down your end of the world ... ;~} )

Anyways, I took a walk this morning and noticed a *lot* of efflorescence on house brick courses below the dpc, so I guess that there's got to be something to it being caused by damp rising up in the bricks, which of course would not be restricted in the case of a garden wall, there not being any dpc. I suppose that we have had quite a wet winter, so I guess that the ground is probably pretty damp. So the other question now, would be, is the white deposit something which is being driven out of the bricks by the water rising up through them and evaporating off the face, or is it something that is in solution in the water, that is then left behind as it evaporates ? With one of the walls that is particularly badly affected being at least 20 years old, I would have thought that anything actually in the structure of the brick, would have been long since driven out. Curious ...

Arfa

[Arfa Daily]

LOL !! I don't know about stamping "LBC" into the frogs, how about "CFL" ?

Arfa

[Gib Bogle]

Not racist ... but a kiwi is a shy, nondescript, flightless bird that only ventures out at night, and has a long beak that it is always sticking into everything. ;-)

"Efflorescence is a white crystalline or powdery, often fluffy/fuzzy deposit on the surface of masonry materials like concrete, brick, clay tile, etc. It's caused by water seeping through the wall/floor/object. The water dissolves salts inside the object while moving through it, then evaporates leaving the salt on the surface."

I hadn't realized that salts could be dissolved out of brick, thinking that the firing would lock them in. Perhaps it's a question of type of brick and firing temperature.

[Clot]

Yes, this backend of the winter has been quite wet and the watertable will be high which will cause moisture to rise within the brickwork. Your comments about garden walls not having DPCs has made me ponder a bit. If we are talking freestanding agrden walls not supporting earth behind then most walls that I have seen usually have at least a course of engineering brick, if not two or in some cases a plastic DPC. I know of two from personal practical input.

When it comes to a retaining wall, I built one in a former property 30 years ago where I built a cavity wall with a DPC to both leaves and a plastic membrane against the earth with a plastic DPC below the capping stones. I last saw that wall circa 15 years ago when visiting a former neighbour and it was fine. Spending an idle moment recently, I looked on Google Earth and it would appear that the wall is still standing. If not, then the footings I put in were reused!

I often wonder about efflorescence. Fortunately my house suffers from none though others in the road do. Some high up in the structure for many years which is presumably due to bricks being stacked in water or very wet ground before construction. Even with rain hitting the external surface of the brick to an extent allowing salts to be washed down the wall and also efflorescence to be weathered off by wind gradually, it will (I will avoid the frequently used spelling here) surely take decades for absorbed salts to be leached and weathered out?

Despite the gradual process, spalling will occur. I was very fortunate to be aware of the potential, inspect the construction of my then new build and to be vigilant immediately after completion. I found several bridges of the cavity from both signs inside and out which I got the builders to resolve.

You've heightened my concern, dare I venture out after having hibernating this winter?

[Arfa Daily]

Interesting comments from both yourself and Gib Bogle. Thinking about it, you are right that there is often a course or two of blue engineering brick at the bottom of a freestanding wall. When I'm next out, I will check to see if any of the badly afflicted ones have this. As far as it taking "decades" to drive the salts out of the bricks. I would have thought that it would have been much quicker than that, but maybe not ?

Arfa

[PeterC]

I'll be interested in this, as my ex-council house has blue bricks as DPC; it's about 55 years old, but I've not noticed any dicolouration. Every Autumn I brush the DPC and above to remove any splashed-up bridging debris from the outside.

[Arfa Daily]

Out of the car walking this morning, and had occasion to go past the wall that first drew my attention to this, and stopped to have a closer look. It

*is* a retaining wall, and it has two courses of high density orange engineering-type bricks at the bottom, which is why they were not immediately obvious from the car. Below them, to pavement level, are a couple of courses of regular facing bricks. There are drainage pipes let into the wall at regular intervals. The white surface bloom is between the h.d. brick courses, and about half way up - below the drains, so that would indicate that it is down to excess dampness in the retained soil. I wonder if the fact that snow lay on the ground for a week, and only melted and dissipated very slowly, has anything to do with creating this situation, which I can't recall having seen on this particular wall, for years in the past ?

Arfa

[PeterC]

Seems reasonable, as the water was released over a long period and evaporated slowly, thereby giving more time (even at low temperature) for dissolution of salts.

I realised many years ago that building materials are not suitable for use outside. The low rate of degradation is due to the equilibrium between, mainly, wet and dry, so extra rainfall isn't a prerequisite, only shorter periods of dry weather. (The above applies to other things: an old GF has 2 allotments and also does scientific research on plants and she's really noticed the difference due to the lack of time to dry causing some crops to be adversely affected).