Puffing Bricks

[Lady_Mari]

We are in the process of fixing laths to the now cement free walls in the sitting room prior to lime rendering.
I have noticed that when drilling into some bricks I get little puffs of the brick dust (other half refers to this as farting bricks).
I would like to know if this indicates moisture within?

 

[Penners]

I would have thought that damp would have tended to make the dust cling together in a loose "plug", rather than appearing as dry dust.

I know exactly what you mean by the puff of dust when drilling bricks. I've always just assumed that it's a build-up of ground-up brick that is just thrown out by the auger effect of the drill's flutes.

But maybe more expert people will have a different view.

 

[Lady_Mari]

I'm sure you are right, Penners, but I am still curious as to why some of them puff but most of them don't.

 

[Penners]

Well, bear in mind that a brick is far from homogenous. I suspect (and it's only my amateur theory) that the puffers perhaps have a lump of something hard in them that causes a brief backup of dust, and then releases it suddenly.

I still don't believe that the puff necessarily indicates dampness in the brick.

Any experts got a view?

 

[Nemesis]

I suggest it's because bricks are made of natural material, clay, and different firings may bring varying degrees of hardness etc within the brick. The outer face is the hardest.

If it ain't broke leave alone, can't see how it has anything to do with damp unless the bricks are obviously damp and degrading.

 

[Lady_Mari]

My other half thought it might be an indication of dampness as it only seems to happen with the lower bricks where he's been attaching battens to fix the laths to. They are nothing special just lbc's.

 

[Andrew Bodenham]

Lady_Mari,

I too have experienced this phenomenon in brick and stone, and it certainly seems to occur more frequently in damp materials.

The displaced brick dust clumps together, clogging the flutes of the drill. Friction at the business end heats up the drill, boiling off moisture in the brick into steam. The resultant pressure escapes with the characteristic puff of dust. Sometimes you will see condensed moisture building up around the mouth of the hole as water is driven out.
The masonry nearer the ground tends to be damper, hence your observation about location.

It's not a problem as such.

 

[Lady_Mari]

Thanks Andrew, that explains the phenomenon very well & I will tell my other half (Lord Tom) that he was right after all.
Thank goodness we got all the concrete off when we did!

 

[Penners]

Told you you needed an expert!

 

[Lady_Mari]

Indeed you did - rather than hazard a guess....

such as

If it ain't broke leave alone, can't see how it has anything to do with damp unless the bricks are obviously damp and degrading

Fortunately Andrew was able to confirm Tom's suspicions.

We live & learn again & again!

 

[Nemesis]

Possibly had your initial post said these were at the base of a wall and damp it would have put the query in context.

Ceramic is odd stuff - and bricks are ceramic. Firing of bricks in the past was not always a precise art. Sometimes bricks were made and fired on site in centuries past. Ceramic is a natural material also, and it varies. They have an outer face and an inner core, which can at times vary in consistency.

Yes I do have some expertise in ceramics, although I have not practised it for a long time.

If the wall is obviously damp then clearly some 'fixing' needs to be carried out. Hopefully the lime will cure the damp, and no degrading of brick will occur. In bad cases these can crumble and require replacing. If they aren't then the problem isn't acute.

 

[PC]

This puffing brick phenomenon is caused by the action of the drill and is not related to moisture in the masonry, it will occur in any substate and can sometimes also occur in timber.

I here that this happens quite a lot when certain damp proofing companies drill the bricks, to install a chemical damp proof course, into dry bricks.

Blimey did I really say that.............................wash my mouth out !!!

PC

 

[Nemesis]

Tut PC - problems with the damp proofing industry?

Whatever will you say next!

 

[Matt Green]

If you think about it: if the masonry was wet, the dust would coagulate.

You see it a lot when you drill into masonry to take damp samples. the damp ones are sticky, the dry ones are dry and dusty. Crazy huh?


Matt.