White on bricks

[Willy87]

Hi all it’s the first winter in our new home its a 1970 ex council property we’ve been having some really heavy rain the last few weeks with strong winds and I’m just starting to notice white staining on the exterior brickwork walls are 50mm cavity and don’t seem to have any problems with dampness inside just wondering what is causing it and if they is anyway to rectify. I will add the house is currently not lived in as we are renovating thanks

 

[^woody^]

It needs repointing

 

[Willy87]

Is that what’s causing the white on the bricks do you think? What would be the best mix to use for repointing in your opinion thanks

 

[Willy87]

Do you think it will be ok for this winter as it’s not ideal conditions for repointing at the moment thanks

 

[blup]

The white patches are likely salts deposited through efflorescence, it may have been going on for years, harmless AFAIK. Repointing may help but the salts are mostly contained in the brick.

Blup

 

[^woody^]

.... and what brings the salts out? Defective pointing

 

[Willy87]

So pointing should cure my problem? What is the best mix to use thanks

 

[blup]

The recent rain has been drawn into the brick, absorbed the salt and the solution has been drawn to the surface. The water evaporates and the salt is left. I don't think it is a problem provided there is no other source of water ingress like a dripping gutter.

Woody will advise you on the correct mortar mix.

Blup

 

[^woody^]

So pointing should cure my problem? What is the best mix to use thanks

No.

The poor pointing has exposed the brick arises which is a significant factor in walls efflorescing. You should also check for leaking gutters or verge above

You have the problem now for life, but repointing will normally stop it getting worse.

4:1 sand cement, but it's how the joint is finished which is important, not the mix.

 

[Willy87]

Thank you what do you mean how the joint is finished how compressed and smooth it is? What would happen if it was lime mortar currently and not sand and cement thanks