Salts on outside of wall?

[DaveG]

Hi all, here’s a picture of the exterior wall on the front side elevation of the house. It occurred to me that the wall looks a bit white, like there’s salts on it.
The interior room on this wall is quite damp but I’ve not stripped wall paper or anything in there yet because I’m wanting to just do the one room at a time and I’ve already started on the front room on the other side of the house.
Just wondering if these salts could be moisture trying to escape on the outside of the wall based on the inside being tanked with cement slurry and gypsum plaster? The height of the discolouration seems to roughly correspond to me.
Other room I’m doing has concrete floor laid on polythene sheet and the slurried exterior walls which I’m in the process of removing so assuming this room will be exactly the same!

 

[DaveG]

Pointing had all but disintegrated in places!!

 

[Stevers]

That looks very familiar!

Unless it's drying there wouldn't be salts, the salts should sweep off, and I do try and collect them, with the hope that don't come back to haunt me. Mortars should be soft and sacrificial, and it looks like yours has done it's job and is ready for some brick repairs and a bit of patch repointing in something equally gentle.

That bit of rendered wall in the corner might need a close look at though as that could be affecting your house wall.

 

[DaveG]

So the salts are an indication the wall is trying to dry out? My guess is it’s fighting a losing battle with high outside ground levels in this area plus a plastic dpc inside pushing ground moisture into it.
So is soft mortar normal?
I was under the impression that it’s soft because of being damp and if the wall were nice and dry the mortar would be too?

Interesting you mention the rendered wall there as I was working in this area today and spotted a small hole and what looked like the render almost bubbling out from the wall so I decided to dig a bolster in there and hack away. Underneath I revealed more lovely stone wall so that’s yet another project to add to my list. Best I don’t destroy too much in one go though hey?
I’d initially thought of trying to channel out a small air gap there to aid breathability but I guess if it were taken back to the stone it wouldn’t do any harm remaining attached to the corner of the house there

 

[Stevers]

Salting has been a sign that a wall is drying out in my basement. Outdoors it's more likely to be washed off by the rain or just permanently in solution in a damp wall. There are also lichens that can look like salts. Mortar should always be softer than the stone or brick, and that is easy to achieve with a lime mortar including NHL.

Your mortar looks like it's a lime/ash mortar and it's possible for that to blow eventually as the ash part of the mortar may have all sorts of contaminants that are not ideal. A repointing job with a soft lime mortar will outlast a hard cement mortar as the latter is likely to cause the stone and brick to decay and the hard mortar will shrink, crack and then start to fall out.

 

[malcolm]

Is that cement mortar? When you get a load of salt it tends to be the wall is soaking wet and trying to get rid of water. If it were lime mortar the wall shouldn't be soaking wet in the first place.

 

[DaveG]

Is that cement mortar? When you get a load of salt it tends to be the wall is soaking wet and trying to get rid of water. If it were lime mortar the wall shouldn't be soaking wet in the first place.

I can’t be sure to be honest but to me the mortar looks like lime because it’s quite grainy. It looks like it’s had a black ash added to it which also looks quite consistent with the lime plaster on the upper sections of wall indoors but I’m no expert. Having seen examples that I know are cement mortar it’s not smooth like that nor does it have that squared finish I see some have.
The stones themselves are not breaking apart like when they’re trapped in moisture but there’s definitely moisture there. I don’t think the concrete slabs right up against the wall are helping matters mind you