Repair/ dehumidifying render mortars/ desalination solution

[Morakot]

I am looking for a repair mortar that has a decent water vapour permeability coefficient.

 

An internal wall has a small damp patch with visible salt marks (superficial efflorescence). The source of the dampness is removed and the cement-based plaster needs replacing in parts.

 

Looking at what is at offer here is rather confusing; manufactures seem to market on two points "sealing" and "strength". Comparing fibre-reinforced repair mortar on offer in Thailand with one sold in Italy, I'm slightly puzzled and wonder whether I'm comparing apples with oranges.

 

Also desalination solution (like this) seems not readily available in Thailand either.

 

What's going on here?

 

ITALY-MONODRY_0116_ENG.pdf

THAILAND-24 (732).pdf

Edited October 10, 2016 by Morakot

[eyecatcher]

If you have already removed the source of the dampness,then surely you are 95% there and simply need a patching up material.

there should be no real need to worry about salts, desalination, fibre reinforcement.

 

Unless your original cement render is blowing then you can simply clean it; i doubt that it has gone black if salts are coming out but if it has, then just use bleach and let the wall dry.

 

Those two products. well the Italian product is a pukka renovating plaster. they would use this after a wall had suffered from rising damp and more usual its applied after a chemical injected dpc. the whole wall plaster  would be removed to a metre high.

this plaster already has the anti salt properties included; whereas a cheaper (lanko) patching product would probably need the desalination solution/water seal.

unless you intend hacking off a substantial amount, then there is simply no need to use pukka renovating plaster.

 

if it were me and I was confident the source of the damp had been addressed then I would patch up in something similar to the original, a patch in anything different will be as obvious as a bowling ball in a bag of diamonds.

[Morakot]

Thanks very much eyecatcher for your reassuring reply!

 

There were black stains in the immediate area where there was direct water exposure. I'm not much worried about this. By the looks of it, there are surface salt deposits much higher at the wall, which I assume happened though capillary rising damp. This is the alarming part; as I understand, the salt creates secondary dampness through attracting air humidity (with insufficient ventilation) and can damage the wall even if the source is removed.

 

The acrylic paint is completely blown off in the salt affected area, but the plaster is mostly intact. At the moment the plaster repair is minor and will only be where I ripped off the skirting boards. I have a bucket of that LANKO 731 pre-mix and it will not be used at visible places.

 

I would like to apply the desalination solution where there was salt. But I have not seen anything like it here. What kind of "water seal" do you recommend? How does it work? I'm not intending to repaint the wall with acrylic paint, but would like to try a lime-based skimcoat; would that work with a water seal solution?

 

 

 

Edited October 11, 2016 by Morakot