Noticed in an earlier thread that a poster was advised to use lime instead 
of cement based mortar on a victorian house.
Is this a brick type issue?
When did cement based mortars take over?

TIA

Phil

"Christian McArdle"  wrote in message 
news:43257b0d$0$12179$ed9e5944@reading.news.pipex.net...

>> Noticed in an earlier thread that a poster was advised to use lime 
>> instead
>> of cement based mortar on a victorian house.
>> Is this a brick type issue?
>

There are other issues of course. Lime mortar is lighter in appearance than 
cement, so
using cement to repoint bits of a lime mortar bulding will look ugly. Also, 
it is said that
it is breathable, whereas cement is not, so a lime mortar render can let out 
damp that enters
via a crack in the render, whereas damp that enters through a crack in 
cement render is
stuck, causing penetrating damp and rot in the walls.

Andy

In article , phil@dropthespam.com 
says...

> Noticed in an earlier thread that a poster was advised to use lime instead 
> of cement based mortar on a victorian house.
> Is this a brick type issue?


Old bricks are often soft and porous, while cement mortar is harder and 
less permeable to moisture.  The mortar should be the weak link in a 
wall or the bricks may start to fail, or sometimes cement pointing will 
just fall out in large pieces if the wall moves.


> When did cement based mortars take over?
> 

Lime was still extensively used up until WWII.

On Mon, 12 Sep 2005 13:50:26 +0100, "TheScullster"
 wrote:


>Noticed in an earlier thread that a poster was advised to use lime instead 
>of cement based mortar on a victorian house.
>Is this a brick type issue?
>When did cement based mortars take over?


Lime based mortar is softer than concrete and allows a certain amount
of movement in a wall.

In days gone by, pointing was intended to be a sacrificial
material-the intention was that it'd be replaced every 50 years or so.


Usually, modern builders/surveyors see weathered pointing as a fault
and replace the lime mortar with hard wearing cement based mortar.
This is a mistake.

Often, when walls are re-pointed with concrete you end up with cracks
in the softer bricks as the mortar has no 'give'. This leads to
moisture getting in, bricks having to be replaced etc..etc.

If you have lime based pointing and it's wearing away then it is doing
its job correctly. Have it re-pointed with more lime based mortar and
you will get no problems in the furure.

sponix

On Mon, 12 Sep 2005 15:05:51 +0100, Rob Morley 
wrote:


>Old bricks are often soft and porous, while cement mortar is harder and 
>less permeable to moisture.  The mortar should be the weak link in a 
>wall or the bricks may start to fail, or sometimes cement pointing will 
>just fall out in large pieces if the wall moves.
>
>> When did cement based mortars take over?
>> 
>Lime was still extensively used up until WWII.


I remember a pair of semis being built across the road from my school
entrance and the kids had previously been used to walking across the
site as a short cut. There was a big pile of grey powder on the site
with a notice that said "This lime will burn your hands". It would
have been Ca. 1955 in Leeds

DG

Thanks to all respondents for illuminating discussion.

Phil

In article ,
	Derek ^  writes:

> On Mon, 12 Sep 2005 15:05:51 +0100, Rob Morley 
> wrote:
>>Old bricks are often soft and porous, while cement mortar is harder and 
>>less permeable to moisture.  The mortar should be the weak link in a 
>>wall or the bricks may start to fail, or sometimes cement pointing will 
>>just fall out in large pieces if the wall moves.
>>
>>> When did cement based mortars take over?
>>> 
>>Lime was still extensively used up until WWII.
> 
> I remember a pair of semis being built across the road from my school
> entrance and the kids had previously been used to walking across the
> site as a short cut. There was a big pile of grey powder on the site
> with a notice that said "This lime will burn your hands". It would
> have been Ca. 1955 in Leeds


Portland Cement was too expensive for widespread use in general
mortar until 1920's, when it starts appearing near the production
sites initially, but took a long time to work its way across the
whole country.

-- 
Andrew Gabriel

s--p--o--n--i--x wrote:

|| Usually, modern builders/surveyors see weathered pointing as a fault
|| and replace the lime mortar with hard wearing cement based mortar.
|| This is a mistake.

How can you tell which is which?  Does it look different?

I have a 50's built semi and the front garden walls (like the rest of the 
estate) are falling apart.  The bricks are sound, but the motar between them 
seems to have lost it's 'bond'.  Its crumbly.

Some of this is due to no capping being used, just bricks on edge so the 
failure is more pronounced where the weather gets to them.

If I rebuild the crumbling sections, should I use lime or cement?

Dave

david lang wrote:

> I have a 50's built semi and the front garden walls (like the rest of the 
> estate) are falling apart.  The bricks are sound, but the motar between them 
> seems to have lost it's 'bond'.  Its crumbly.



Is the wall still structurally sound? If not, pointing is point-less.



> Some of this is due to no capping being used, just bricks on edge so the 
> failure is more pronounced where the weather gets to them.


Bricks on *edge*? Do you mean the top course?


> If I rebuild the crumbling sections, should I use lime or cement?


Both.

> How can you tell which is which?  Does it look different?


Yes. Cement mortar is much, much harder.


> If I rebuild the crumbling sections, should I use lime or cement?


Use what was originally used. 1950s front garden walls could have been lime
or cement based.

Christian.

"david lang"  wrote in message 
news:XDoVe.1766$Kk3.640@fe1.news.blueyonder.co.uk...

> s--p--o--n--i--x wrote:
>
> || Usually, modern builders/surveyors see weathered pointing as a fault
> || and replace the lime mortar with hard wearing cement based mortar.
> || This is a mistake.
>
> How can you tell which is which?  Does it look different?
>

Lime mortar is usually white. It may have weathered a bit but it's still
lighter than portland cement. Scrape a bit off and look at an unweathered
surface, I've seen it look anywhere from off-white to creamy. Of course,
the type of sand or grit used with it might colour it slightly different 
from
locale to locale.

Andy.

TheScullster wrote:

> Noticed in an earlier thread that a poster was advised to use lime instead
> of cement based mortar on a victorian house.
> Is this a brick type issue?
> When did cement based mortars take over?
>
> TIA
>
> Phil



Also there is the question of foundations and movement. 100 yr old
houses had very shallow foundations, and movement in these is normal.
With cement mortar, the weaker bricks break. With lime, the lime
cracks, but unlike cement it microcracks, then self heals. It reacts
with CO2 to grow hard crystals across the crack, so it heals itself,
with no damage done.

Also cement tends to pull the surfaces off the bricks in time, and this
loss of fireskin causes the brick to get wet, and crumble when it
freezes. Over the years bricks thus affected will slowly crumble away.

And finally theres damp. Water that gets into the wall, as is
inevitbale, evaporates out from lime mortar. It doesnt with cement, so
old walls built with porous bricks and no dpc are more prone to damp is
cement is used.


Note about cement lime mixes: almost all such mixes fail prematurely.
The only one that is ok is 1:1:6.


NT

Andrew Gabriel wrote:


> Portland Cement was too expensive for widespread use in general
> mortar until 1920's, when it starts appearing near the production
> sites initially, but took a long time to work its way across the
> whole country.


While we're having lessons - what's the difference between Portland and 
other types of cement?  I'm sure Portland is the only type I ever see at 
my usual suppliers.

David

> While we're having lessons - what's the difference between Portland and
> other types of cement?


Well Ordinary Portland cement is what we would generically call cement,
although naturally occuring Pozzolana is also often called cement,
especially in historical contexts (i.e. Roman construction). Portland cement
is a manufactured material actually based on lime, but mixed up with clay
(or sand) and baked, to modify its qualities, making it much quicker
setting, non-porous and hydraulic (able to set under water quickly).

Some lime mortars have OPC in them, whilst some have lime only (plus sand,
of course). Even with OPC mixed in, they are much more porous and suitable
for older buildings, as they allow the building to move and prevent soft
bricks from cracking.

Christian.

Chris Bacon wrote:

|| Is the wall still structurally sound? If not, pointing is point-less.

It's the top two or three courses that are unsound, the rest seems OK.  I'm 
talking about rebuilding rather than pointing.

|| Bricks on *edge*? Do you mean the top course?

Yes


||| If I rebuild the crumbling sections, should I use lime or cement?
||
|| Both.

What, cement mortar to rebuild & lime to point?

Dave

david lang wrote:

> Chris Bacon wrote:
> > david lang wrote:
> ||| If I rebuild the crumbling sections, should I use lime or cement?

> || Both.
> 
> What, cement mortar to rebuild & lime to point?


No, 1:1:6! I shouldn't put a "hard hat" on it IIWY. If you use
cement mortar to build, it's no use to have lime pointing.

bigcat@meeow.co.uk wrote:


> Also cement tends to pull the surfaces off the bricks in time, and this
> loss of fireskin causes the brick to get wet, and crumble when it
> freezes.


I would have said "cement pointing is much harder than the lime
the wall was originally built with; the excessive force on the
edges of the bricks causes spalling, which is exacerbated when
water is then allowed into the brick and is subject to the
freeze/thaw cycle".