Talk Salt to me please!

[Willsa]

Hi gang!

This is where I'm at with my dry-rotting terrace:

I removed a good portion of the "damp-proofing" concrete from the lower parts of the walls downstairs. It's the original lime from 1m and above.
There was plenty of dry rot and some areas of active woodworm behind the cement and in the woodwork close to the ground level.

I've left the brickwork exposed to dry for a few months now and have repaired the roof and all the (very!) faulty water goods. I'm ventilating and heating.

The brickwork is drying out nicely BUT!
The salts started appearing... A part of drying out I suppose... I just let the process happen, so I can see better what I'm dealing with.

I don't think it's good! Large, shard-like crystals have grown. Sparkly, but not of the type I like...
From digging up the Internet, the crystals appear to be Magnesium salts (Epsom salts for my bath).

I have inherited substandard concrete floors - Magnesium is not good news for that either, as I gather.

Crystals =rapid drying of high concentration salt solutions.

So was it Magnesium rich ground water trapped behind the cement, not evaporating, feeding the fungus, sweating... And now rapid drying?
Is the water still a current issue?

The salts are pulverising the already weakened bricks, here's a pic or two:

 

[Willsa]

At some point I'll have to wash those bricks in fungal biocide, maybe do some other "wet" works.
Worried about wet-dry cycles...

What would you make of this in your house?

Thank you in advance!

 

[malcolm]

Wow! That wall must have been soaking wet for a long time. I've never seen salts like that. I'm guessing the photo is of the outside of the wall? Do they brush off?

The damage was probably done while the wall was stewing in water. The minerals will have probably dissolved out of the bricks themselves. I wouldn't worry about getting it wet as it's only the surface you will affect and it looks like it is now good at drying out.

 

[Feltwell]

The salts are a good sign!

They look scary, but it's a clear sign of drying. The water is evaporating, the salts have to go somewhere, if the bricks were still sodden then the salts would stay dissolved within the moisture.

Good idea to brush them off with a dry brush if you can.

 

[Willsa]

Oh, that's good news! Any sentence with "drying" is

Was worried if the bricks could be still damp & forming crystals at the same time, but mind's at peace on that now, thanks!

*Thus far I can confirm that removing the hard "waterproofing" cement and plastic vapour sheets from the walls has helped the walls dry (even in winter).
The dry rot shrooms didn't like fresh air either - it has dried up by just removing the cement and and the rotted wood. No chemicals deployed. But I'll do a round of basic masonry biocide on a warm summer's day. And a Pagan spell. The low-cost approach

 

[Willsa]

Wow! That wall must have been soaking wet for a long time. I've never seen salts like that. I'm guessing the photo is of the outside of the wall? Do they brush off?

The damage was probably done while the wall was stewing in water. The minerals will have probably dissolved out of the bricks themselves. I wouldn't worry about getting it wet as it's only the surface you will affect and it looks like it is now good at drying out.

It's all internal walls, where the dry rot was spreading mostly.
Those same internal walls have damp proofing injection holes and were plastered in hard cement.

Something(!) must have been very wrong here but I won't necessarily find out what, as the brick is drying out wonderfully since me being in this house.

Once I'm sure the drying cycle is done, I'll repoint and replaster with lime internally. Hopefully without issues. Hopefully.
The moisture can't escape via the concrete floor, so the walls will have to try and do their best!

 

[Willsa]

I quite enjoyed reading up on these specific salt crystals:

They are Magnesium sulphate salts also known as Epsom Salt.

Magnesium Sulphate usually starts as a mineral of marine evaporation type. The kinds of minerals left behind by lakes, seas and rivers evaporating.

When Magnesium Sulphate was found on Mars, that was the indicator of there having been biologically rich water at some point.

I suppose my local bricks would have had local clay used and that would fit the bill for being a river evapourite.

The minerals in the clay would be stable until... Water. The minerals dissolve.

Rapid evaporation (count me surprised it happened in winter) forms Magnesium crystals in the brick pores, that expand and destroy the brick.

I read a scientific paper on bricks soaked in different salt solutions and dried. Many times over. Then tested for damage.
The Magnesium salts were noted for large crystals and pulverising the surface layer to dust. Seems like deep cracks are usually not observed, so might get away with it!

As all salts, Magnesium Sulphate is hygroscopic (attracts moisture) so I'll brush away as advised!


I'll recite this to the next builder who steps in my hall. Straight on the list of bening but eccentric

 

[steveb]

Somewhere behind this father Christmas beard I have a brick..

This is a sleeper wall under the (rotted out) wooden floor

 

[mardinor]

The only 'wet work' I'd suggest is for the builder who added the cement render...

 

[Stevers]

Very impressed by your crystals that put mine to shame! Did your dry rot come with fruiting bodies and a sweet smell?

There are other theories about the name, but I was taught that dry rot is called 'dry' because once it starts it can spread to areas that are drier because it can transport the moisture it requires in root like hyphae. Dry rot is typically found under floors and in unventilated voids, whilst 'wet' rot is found in windows, exterior wood work, and in my case in the wall plates under the joists of my well ventilated floor. In my experience where there is wet rot there will be woodworm too. :-(

The result of both types is dry crumbly wood, but dry rot is much, much scarier.

 

[Matt Green]

There was plenty of dry rot .... in the woodwork close to the ground level.

Unlikely at ground level with that much salt. Brown rot decay, probably cellar rot.

 

[steveb]

I have no idea what kind of rot I had to be honest. Everything was wet and a lot of what was left was the consistency of compost. I have weird mushrooms growing under the floor in the kitchen that I can't get to - hopefully I have made some more through vents with a bolster and hoovered out a load of building detritus through the new holes which should help. And fixed a water leak from the flat above that was under my floor (their supply pipe was leaking).

I had some interesting kind of I assume fungus or plant that was growing between the old stone wall and the plastic tanking membrane - covered a very large area with long and 1mm sized "roots" over a wide area.

This is some of the timber that was left. The outer 2 pieces were on the sleeper wall, the middle one was a 4x2 joist rotted down to 2x2 where it met the sleeper wall (or didn't meet any more, as the case was)

 

[Willsa]

Very impressed by your crystals that put mine to shame! Did your dry rot come with fruiting bodies and a sweet smell?

The sodium chloride salts cause deposits more like the white tide marks. Magnesium salts grow crystals.
In my case, I'd rather not see crystals - apparently Magnesium ain't a friend of concrete and I do have concrete floors.

Always surprised what sort of nose would describe the dry rot smell as sweet
To me, it smells like the very essence of an earthy mushroom plus a pungent mould - like odour. It takes my breath away, it's so strong! I used to go wild-mushroom picking and the smell is similar to that of the root (mycelium) of the wild shrooms.

Dogs can be trained to identify the locations of dry rot. With a bit of training, I could do it too. 50 quid to sniff about an average 3 bed terrace

 

[Cubist]

No disrespect intended but please don't come sniffing round here.