Hello.

I am totally confused! I need to do some repointing on my Edwardian semi.
From investigation I'm led to believe that lime based mortar would have
originally been used. However, there seems to be lots of, often
contradictory, information about the type of mortar I should use.

1. Use 3:1 lime mix. Some say hydrated lime mixed dry is OK, others say
the hydrated lime needs to be soaked in water for as long as possible,
others say hydrated lime is unsuitable and you should use commercial lime
putty.

2. Use 1:1:6 cement:lime mix. Or use 1:2:9 cement mix.

3. Sand. Some say use sharp sand, others builders sand, others a mix of
the 2.

.....and so it goes on.

Simply, the more I search, the more differing opionions I seem to find.

I've taken a picture of the existing mortar -
http://steve.blokes.org.uk/p15678304.html

I'd be grateful for some conclusive guidance as how to go about producing
a mortar mix to as closely replicate the existing mortar.

Cheers,

Steve.

"Steve" wrote in message
news:7b7f9699466be3c5205af2c91afcfa40@localhost...
Hello.

I am totally confused! I need to do some repointing on my Edwardian semi.
From investigation I'm led to believe that lime based mortar would have
originally been used. However, there seems to be lots of, often
contradictory, information about the type of mortar I should use.

1. Use 3:1 lime mix. Some say hydrated lime mixed dry is OK, others say
the hydrated lime needs to be soaked in water for as long as possible,
others say hydrated lime is unsuitable and you should use commercial lime
putty.

First off, I am not an expert: with that disclaimer, I shall comment on your
questions.
I have heard many opinions on the amount of time needed to soak lime prior
to use. The longest I have heard to date is 60 days, plus another 28 after
you add the
sand to make lime! All I can say is it still sets if you mix it with water
24 hours ahead
of use, which is what I have done. The hydrated lime mixed with water is
called
'lime putty' by the way, whilst I believe that the lime putty with sand
added to it is
called 'rough stuff' or something daft. Lime putty and rough stuff will keep
indefinitely
if kept wet and away from the air. It takes about six weeks to set, so be
patient.
To my knowledge, what goes into commercial lime putty is hydrated lime, that
is
they take quicklime, CaO, add water to slake it ( standing well back ) then
you get
hydrated lime, which is probably CaOH2O or similar, which is what you get in
a bag of
hydated lime. AFAICS, the only difference is the length of time it's been
soaking in water,
and I'm not entirely sure what reaction is supposed to be taking place when
lime putty is
just standing around out of contact with the air ( lime mortar sets by
reation with carbon
dioxide, making calcium carbonate ).

2. Use 1:1:6 cement:lime mix. Or use 1:2:9 cement mix.

I have used the first of these mixes as well, using white portland cement as
opposed
to the grey stuff. It works too, and goes off quicker, though whether it is
as flexible and
permeable as a straight lime mortar I don't know.

3. Sand. Some say use sharp sand, others builders sand, others a mix of
the 2.

I used sharp sand ( silver sand ) as I wanted a white mortar. I have to say
that the lime
mortar ( I assume it is simple lime mortar and not lime-cement mortar ) used
on my
house originally looks to have been made with 'lime grit' instead of sharp
sand. As I
understand it, lime grit is a wide range of sizes of rounded river
particles, some of which
are quite large ( several mm ). I could not source any so used sharp sand
( silver sand ) as
it gave me the colour I wanted. It is not as nice to work/adjust/handle as
builders' sand, but
I have managed to lay bricks with it.

....and so it goes on.

Simply, the more I search, the more differing opionions I seem to find.

I've taken a picture of the existing mortar -
http://steve.blokes.org.uk/p15678304.html

I'd be grateful for some conclusive guidance as how to go about producing
a mortar mix to as closely replicate the existing mortar.

Looks like your mortar uses lime grit: I have no idea if it is still
available. I couldn't find any.
How much fidelity do you actually want? If you are going for a perfect match
I think you will
need to spend some time searching about for grits/sands etc and try a few
mixes out. It
won't look the same even if you match the original mix, as it has weathered.
Brand new
lime mortar made with silver sand is going to be a lot whiter than what you
have, though it will
settle down a bit over a year or two, especially if the rain can get to it.
You can get cement colourants to tweak the colour of the mortar if need be,
but you'd have to
be careful about matching batches.By the way, keep the lime mortat covered
for a week
whilst setting, as it needs moisture to set.

Andy.

In article ,
"andrewpreece" writes:
I used sharp sand ( silver sand ) as I wanted a white mortar. I have to say
that the lime
mortar ( I assume it is simple lime mortar and not lime-cement mortar ) used
on my
house originally looks to have been made with 'lime grit' instead of sharp
sand. As I
understand it, lime grit is a wide range of sizes of rounded river
particles, some of which
are quite large ( several mm ).

In Victorian/Edwardian times, sand was not so accurately graded
as it is today. I suspect the sand in the lime plaster was
probably the finest available at the time, and even that has
large lumps in it which I've found when taking bits off. That
must have made it a real bugger to get flat and polished, but
they seem to have managed even so.

A brickie (actually he teaches building, but loves doing brickwork
too) at the other end of my terrace said if they're trying to get
an authentic sand to match ~1900 properties, they usually do it
by mixing various current sand grades together, to get the large
variation in particle size which sand used at the time had.

--
Andrew Gabriel

"andrewpreece" wrote in message

lime mortar sets by
reation with carbon
dioxide, making calcium carbonate ).

Chalk being well known for its water resistance anf longevity


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Steve wrote:

Hello.

I am totally confused! I need to do some repointing on my Edwardian semi.
From investigation I'm led to believe that lime based mortar would have
originally been used. However, there seems to be lots of, often
contradictory, information about the type of mortar I should use.

1. Use 3:1 lime mix. Some say hydrated lime mixed dry is OK, others say
the hydrated lime needs to be soaked in water for as long as possible,
others say hydrated lime is unsuitable and you should use commercial lime
putty.

2. Use 1:1:6 cement:lime mix. Or use 1:2:9 cement mix.

3. Sand. Some say use sharp sand, others builders sand, others a mix of
the 2.

....and so it goes on.

Simply, the more I search, the more differing opionions I seem to find.

I've taken a picture of the existing mortar -
http://steve.blokes.org.uk/p15678304.html

I'd be grateful for some conclusive guidance as how to go about producing
a mortar mix to as closely replicate the existing mortar.

Cheers,

Steve.

The truth of the matter is that any combination of lime, cement, and
sand will more or less set hard and not crumble unless there is a huge
amount of sand and not that much of anything else.

A bag of cement will set all by itself.

Sharp sand is griity, and daoesn;t flow as well as bulders, and has
bigger spaces that tend to make it more porous if you don't use a lot of
cement. Sometimes this is what you want.

Adding lime makes the mixture take l;onger to set, and in a way a full
lime mortar never dies set - it remaions slightly crumbly.

Using a lot of cement fills up the holes between the sand completely,
making the mortar impervious, but according to another poster, it may
crack on setting, nullifying the benefits. Never seen it myself even in
lumps of 100% cement.

For brickwork, you want a mortar that is flwable enough to tamp bricks
down ion accurately, and stays soft long enough to get a decent line
laid, and yet is solid enough not to splump when you lay the next course
over it. and is relatively tough and water resistant.

A lot depends on the bricks too - porous commons will suck the mortar dy
unless soaked first, and cause it to go fairly solid fairly quickly.
Thats someimes useful, as it stabilises the course ready for the next one.

I'd say about 4:1 to 6:1 builders sand to cement makes a decent mix, and
you can add lime and subtract cement.

I never know what I mix to. Its pretty much a half bag of cement a half
bag of lime and about 20 shovelfuls of sand in the mixer..maybe a squirt
of plasticiser or winter mix.

I was laying flagstones on half a bag of cement and 20 shovels of sharp
sand. That came out porous, but hard...at 125kg of cement to 850kg of
sand..thats about 7:1 I make it, weight wise.

So probably my mortars are 3:1 or 4:1 sand to cement. or 6:1:1 with lime?

Something around that area anyway.



,


..

Stuart Noble wrote:

"andrewpreece" wrote in message


lime mortar sets by
reation with carbon
dioxide, making calcium carbonate ).


Chalk being well known for its water resistance anf longevity





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I'm no expert either and did not read Andy's impressive attempt. But check out these guys, if anyone knows lime, they do!

http://www.lime.org.uk/

In article ,
The Natural Philosopher writes:
Using a lot of cement fills up the holes between the sand completely,
making the mortar impervious, but according to another poster, it may
crack on setting, nullifying the benefits. Never seen it myself even in
lumps of 100% cement.

Some previous occupant of my house repointed a couple of areas,
very small fortunately, with 100% cement. It resulted in a neat
crack line all the way along, and was impossible to remove without
damaging the brick faces. You probably wouldn't notice shrinkage
in a lump, but force it into a gap and let it set, and you'll notice
it shrinks lots.

For brickwork, you want a mortar that is flwable enough to tamp bricks
down ion accurately, and stays soft long enough to get a decent line
laid, and yet is solid enough not to splump when you lay the next course
over it. and is relatively tough and water resistant.

A lot depends on the bricks too - porous commons will suck the mortar dy
unless soaked first, and cause it to go fairly solid fairly quickly.
Thats someimes useful, as it stabilises the course ready for the next one.

I'd say about 4:1 to 6:1 builders sand to cement makes a decent mix, and
you can add lime and subtract cement.

Some cement:lime ratios are particularly bad though, with
the cement failing to add strength and preventing the lime's
healing properties from working. 1:1 is safe from this though.

You also need to know if the wall is intended to be one solid item,
or if it's designed to move around. Cement mortar is fine for a
solid wall, but lime mortar walls are not intended to be solid,
and mixing areas of 'solid' cement mortar in to one can cause bad
damage to the wall as a whole.

--
Andrew Gabriel

There are all sorts of reasons why you should not use any Portland
cement on an old house. The arguements between using bagged hydrated
lime and wet lime putty are analogous to the difference between a Rolls
Royce and a mini. They will both get you there but...
When the Victorian and Edwardian houses were built, the quicklime
(limestone that has been burnt in a kiln to change the calcium
carbonate to calcium oxide) was slaked on the building site and used
straight away. It was recognised that leaving the lime putty in the
slaking pit for weeks or months improved it but this was not a
practical proposition in the housing boom around the turn of the 19th
century. The lime was often not very well sieved, hence the large
particles of lime found in old mortars. These days we are just too
careful with the ingredients and find the rough and ready methods of
old difficult to reproduce.

"Steve" wrote in message
news:7b7f9699466be3c5205af2c91afcfa40@localhost...
Hello.

I am totally confused! I need to do some repointing on my Edwardian semi.
From investigation I'm led to believe that lime based mortar would have
originally been used. However, there seems to be lots of, often
contradictory, information about the type of mortar I should use.

1. Use 3:1 lime mix. Some say hydrated lime mixed dry is OK,

No - doesn't produce a nice 'fat' mix

others say
the hydrated lime needs to be soaked in water for as long as possible,

Much better

others say hydrated lime is unsuitable and you should use commercial lime
putty.

Best


2. Use 1:1:6 cement:lime mix.
Not nice to do if the house still has lime mortar intact but does work


Or use 1:2:9 cement mix.
No - cracks


3. Sand. Some say use sharp sand, others builders sand, others a mix of
the 2.

Hard one. Best thing is to take a small sample from the wall and have it
analysed for a match.


I'd be grateful for some conclusive guidance as how to go about producing
a mortar mix to as closely replicate the existing mortar.

If you google for your nearest "lime putty" centre (MikeWye, Oldhousestore,
Bleaklow, etc) they will offer lots of advice.

Steve wrote:
Hello.

I am totally confused! I need to do some repointing on my Edwardian semi.
From investigation I'm led to believe that lime based mortar would have
originally been used. However, there seems to be lots of, often
contradictory, information about the type of mortar I should use.

OK, a few basics.

There are 2 basic types of mortar: lime, and cement. (Lime & cement
mixes are all of the cement type.)


Cement mortars on soft brick cause 3 problems:

1. Bricks breaking due to normal movement. Lime mortars are softer and
will crack instead of breaking the brick, which is very much
preferable. Also lime mortars self heal by recrystallising across the
cracks.

2. deterioration of bricks due to freeze damage.
Lime evaporates damp from the wall, cement doesnt, so water at the
brick surface freezing causes bricks to slowly disintegrate in some
cases.

3. Damp: lime allows the evaporation of damp, cement does to a much
lesser extent.


So lime mortar is much preferred, although cement will work.

Cement mortar: there is only one reasonable choice, 1:1:6. 1:2:9 is now
known fail prematurely.


Lime mortar:

You can mix hydrated bagged lime into a putty, store it in a closed
container for a few weeks and use it 3:1. This is easy and cheap. Other
options are buying lime putty or using bagged lime and water without
storage. Cover the job for a while so hard rain doesnt wash it out
before its hard.


Sand: use whatever the heck you want. From your pic, use the gritty
sand, and add some lil bits of chalk if you can find it and want it to
look the same. What you have is lime mortar, cment will never match it.


NT

"Steve" wrote in message
news:7b7f9699466be3c5205af2c91afcfa40@localhost...
I'd be grateful for some conclusive guidance as how to go about producing
a mortar mix to as closely replicate the existing mortar.

Cheers,

Steve.


If you're really stuck http://www.thelimecentre.co.uk/ will analyse your
existing mortar for £85 (and presumably advise further).

--
LSR

On Tue, 31 May 2005 17:20:04 +0100, "andrewpreece"
wrote:

I have heard many opinions on the amount of time needed to soak lime prior
to use. The longest I have heard to date is 60 days, plus another 28 after
you add the
sand to make lime! All I can say is it still sets if you mix it with water
24 hours ahead
of use, which is what I have done.

Time doesn't affect the setting but affects the workability which is
how easy it is to make it do what you want

The hydrated lime mixed with water is
called
'lime putty' by the way, whilst I believe that the lime putty with sand
added to it is
called 'rough stuff'

Coarse stuff

2. Use 1:1:6 cement:lime mix. Or use 1:2:9 cement mix.

I have used the first of these mixes as well, using white portland cement as
opposed
to the grey stuff. It works too, and goes off quicker, though whether it is
as flexible and
permeable as a straight lime mortar I don't know.

Not and not

3. Sand. Some say use sharp sand, others builders sand, others a mix of
the 2.

Have a look round to see what aggregate is available and then if
necessary mix various things together to get as good a match to the
old as you can. For pointing whether you use sharp or builders sand
isn't nearly so important as getting a good colour and texture match
using a mixture of large, medium and small grains. The original
aggregate probably came from somewhere really local

http://steve.blokes.org.uk/p15678304.html

The bit in the photo doesn't need pointing. Its worth putting off
pointing for as long as you can cos it looks better old

Anna


~~ Anna Kettle, Suffolk, England
|""""| ~ Lime plaster repairs
/ ^^ \ // Freehand modelling in lime: overmantels, pargeting etc
|____| www.kettlenet.co.uk 01359 230642

Anna Kettle wrote:
On Tue, 31 May 2005 17:20:04 +0100, "andrewpreece"
wrote:

http://steve.blokes.org.uk/p15678304.html

The bit in the photo doesn't need pointing. Its worth putting off
pointing for as long as you can cos it looks better old

Anna

that brings up an important point. Where there is cement, do not remove
any sound pointing, only repoint the patches that need it. Removing
cment pointing, unless its falling apart, and unless great care is
taken, damages bricks and leads t their gradual disintegration.


NT