Why do the bricks turn white

Hi All

I was wondering why in very cold dry weather like we are experiencing why do the bricks on my house plus other houses in the vicinity have a white powdery covering on them.

Is this good or bad or nothing to worry about

Spruce

 

The wetting drying cycle causes soluble salts within them to migrate to the surface & crystalise out. If its coming out then thats ok, its when they crystalise out within the masonry it can cause spalling

 

Ta Zigs

I had a feeling this was right up your street


"crystalise out within the masonry it can cause spalling"

does this mean the cement in between the bricks ?


Spruce

 

No, the masonry is the bricks or stone the wall is built from. The bedding mix should be sacrificial to the masonry, allowing salts and water to escape thru it rather than the bricks. Its cheaper to repoint than to replace the masonry.

The bedding mix used to be lime mortar, which is porous and flexable. The cement used nowdays is less porous and rigid, often cracks and allows water to penetrate.

You've probably noticed cement pointing at low level on some walls where the lime has done its job and failed rather than the masonry.

When it gets repointed with cement the water cant get out thru the pointing so comes out thru the masonry instead causing damage, especially in frosty weather.

 

now I understand

ta Zigs the Master Builder of GC

Spruce

 

The front of my house showed salt on the mortar this year. It seems to have faded away now.

 

It's called efflorescence.

 

Morning Zigs

You seem to know fair amount about this kind of thing so ...

our house (built pre 1840 of solid stone walls) has exposed internal stone walls which tend to have the salt residuals on them. They look rather unsightly and bits of stone can flake off (they are Gloucester red sand stones) . Any ideas of how to seal them? I've heard of using linseed oil, would it work?

Thanks in advance for any suggestions

 

For an example of this, come and look at my house.

 

This thread is getting interesting I would of never thought it would

 

Morning HsuH,

Sandstone is an awkward one, if I were doing it properly i'd wet the wall down and poltice it to get as much of the salt out first. I'd only use boiled linseed on an impermeable stone, probably not on sandstone.

Maybe a lime water/casein wash would consolidate it.

 

I Asked this Question to my My Brick Laying Tuter only last week and told me wot Ziggs Said & Scrungee said

its called efflorescence its Also Caused by laying Damp bricks in damp conditions creating the salt to come forward to the front of the brick

I Dont like the look of it either theres loads of this around by us we was told by our tuter to look at buildings and go back and ask questions of our findings or explain wot we had saw and this was one of my questions

 

It did rain a lot when the house was getting built

Spruce

 

You're right Nick, a lot of it is down to money, why waste money on washed sand when sand full of salt is cheaper. Never mind that its going to destroy the masonry a few years later. The cheque will have cleared and the builders long gone by then.

I feel sorry for all the folk that have bought a new build house with stone outer skin recently. They will be looking at complete masonry replacement in 30/50 years. Cement is not compatible with most masonry.

 

My god-daughter mum lives across the road the house is slowly turning green at least I have brick , more ££ to fork out to get it cleaned.

Spruce