Crumbling new Lime Mortar Pointing
ihate...@gmail.com
I am renovating brickwork on my chimney breast. I have raked out the
old mortar, and am repointing with some ready mixed Rough Aggregate 1:3
mix lime mortar.
Now, I left some lines too long before buffing the lime to get the nice
colour and show the aggregate in the mix. Because of this I had to
really rub hard with a brush to get the top layer off. To my dismay,
after getting through a hardened top crust, the underlying new pointing
just turned to loose sand.
OK I thought, maybe I got my pointing wrong, wet the joint too much,
maybe not enough, so I left a bit of the mortar out to dry on a board.
A lump of the lime mortar (after about 1 week drying) about the size of
a two pence piece just crumbled again to sand when I crushed it between
my fingers.
Am I doing something completely wrong here. I know its weaker than
cement mortar, I didn't expect it to be this weak! Have I got a duff
batch maybe?
Thanks in advance for any replies.
James
bi...@biffvernon.freeserve.co.uk
calcium hydroxide. It reacts chemically with carbon dioxide in the air
to form calcium carbonate. This is the hard, strong mineral that you
want. It is what limestone is made of. The reaction proceeds slowly
in the presence of air and moisture. Your hardened top crust shows
that it is happening but it takes weeks, even months, to complete the
process. Your mortar will be much stronger next year if you leave it
alone. You probably have done nothing wrong except shown a bit of
impatience.
One of the many advantages of lime mortar is that it absorbs CO2 from
the atmosphere and requires lower temperature in kilning so contributes
less to global warming than Ordinary Portland cement.
Rick
We intend to use a similar techniqe to point our hosue, so have been
expirimenting to see what happens.
It takes a good while for the mortar to set all the way through, after
a couple of weeks we can see its on its way, but we expect it to take
somewhat longer to completly set.
Rick
Andrew Gabriel
bi...@biffvernon.freeserve.co.uk writes:
> One of the many advantages of lime mortar is that it absorbs CO2 from
> the atmosphere
Well, it absorbs exactly the same amount it gave off whilst
being calcined (burned) during production (ignoring any
produced by the energy required to heat it).
It starts off as calcium carbonate in the ground, and it
ends up as calcium carbonate in your walls, but reshaped
to fit precisely around your bricks.
> and requires lower temperature in kilning so contributes
> less to global warming than Ordinary Portland cement.
--
Andrew Gabriel
Stuart Noble
quality :-)
Stuart Noble
useless for re-pointing.
I would guess that where it is effective the bulk of the mortar never
dries fully due to the skin formed by the initial set. In thin layers
the whole lot reverts to chalk and sand, and my hunch is it won't
improve, however long you leave it.
bi...@biffvernon.freeserve.co.uk
definately the most suitable material for repointing brick and stone
buildings that were built before the introduction of Ordinary Portland
cement. That means almost all building more than 100 years old and a
good many younger ones. Lime mortar does not 'dry', rather it sets by
carbonation of the calcium hydroxide to calcium carbonate, a process
that takes weeks or months. If you don't believe me because you don't
trust me as an expert in this area then please consult English
Heritage, The Society for Protection of Ancient Buildings, The National
Trust, any local authority Conservation Officer or any of the other
organizations whose business is the protection of our built heritage.
Any of these will tell you that using Portland cement to repoint old
buildings presents many problems including irreversible damage. There
would, potentially, be cases where using Portland cement, instead of
lime, to repoint a listed building could constitute a criminal offence.
It is hard to stress strongly enough that Stuart's advice should not be
heeded.
John Rumm
> I would guess that where it is effective the bulk of the mortar never
> dries fully due to the skin formed by the initial set. In thin layers
> the whole lot reverts to chalk and sand, and my hunch is it won't
> improve, however long you leave it.
Leave it long enough and it will work just fine...
--
Cheers,
John.
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BigWallop
"John Rumm" <see.my.s...@nowhere.null> wrote in message
news:42cd208f$0$2884$ed2e...@ptn-nntp-reader04.plus.net...
> Stuart Noble wrote:
>
> > I would guess that where it is effective the bulk of the mortar never
> > dries fully due to the skin formed by the initial set. In thin layers
> > the whole lot reverts to chalk and sand, and my hunch is it won't
> > improve, however long you leave it.
>
> Leave it long enough and it will work just fine...
>
> John.
>
Having never used lime mortar myself, but hearing the different site guys
talking about it on renovations and things, is it true that it's supposed to
mix more to the consistency of putty rather than just normal mortar?
Stuart Noble
I hope James keeps us informed of the progress of his lime mortar as it
carbonates over the years. I suspect it will continue to crumble between
his fingers as it does now.
big...@meeow.co.uk
Is this IMM? If not, theyll probably gang up.
For the OP, lime mortar should idally be kept damp for a few weeks to
hasten its set. It can be covered with sheeting, or sprinkled.
NT
andrewpreece
"BigWallop" <spam.guard@_spam_guard.com> wrote in message
news:Op9ze.64862$G8.2...@text.news.blueyonder.co.uk...
No, when you mix up lime with water you get lime putty, which does rather
have the
consistency of putty, but when that has soaked for a while, you then mix the
lime
putty with sand to get 'coarse stuff', which behaves exactly like mortar.
Andy.
andrewpreece
<big...@meeow.co.uk> wrote in message
news:1120744107.5...@g43g2000cwa.googlegroups.com...
Having used lime mortar, I can testify to its reluctance to set, but give it
about six
weeks and the outer surface will have set sufficiently that you cannot
scratch it
away with a fingernail. For comparison cement mortar reaches 50% strength
in about 3 days.
Andy.
Stuart Noble
> For the OP, lime mortar should idally be kept damp for a few weeks to
> hasten its set. It can be covered with sheeting, or sprinkled.
>
How would keeping it damp hasten its cure? I think you cover it until
the surface has cured/carbonated/dried sufficiently to withstand rain.
Not exactly a practical proposition, which is presumably why hydraulic
lime was used. Maybe the sand also has a pozzolan effect. How would you
ever get a house built otherwise?
BigWallop
"andrewpreece" <andrew...@onetel.net.uk> wrote in message
news:42cd...@212.67.96.135...
it had to stay as a putty consistency to be any good for pointing, which
means that the sand and lime mixture had to be equal in the mix. I like to
learn these things. :-)
big...@meeow.co.uk
At least youre now accepting you dont know the basics of lime mortar.
Thats a good start. Now you can find out. Google is your friend.
NT
Stuart Noble
bi...@biffvernon.freeserve.co.uk
try to learn about lime mortars instead of attempting to be insulting.
BigWallap, you wouldn't want an equal lime sand mix. There should be
just enough, but no more, lime to fill the spaces between the sand
grains. This is a bit tricky to work out because it depends on the
size of sand grains and, especially, whether the sand grains are all
the same size or have a range of grain sizes. In practice you won't be
far from the ideal with a 3:1 sand:lime mix for mortar. For the top
coat of lime plaster a mix with more lime, less sand can be used as
it's then easier to get a smooth finish and strength is not so
important.
Mike
guys
> > talking about it on renovations and things, is it true that it's
supposed
> to
> > mix more to the consistency of putty rather than just normal mortar?
> >
> >
>
> No, when you mix up lime with water you get lime putty, which does rather
> have the
> consistency of putty, but when that has soaked for a while, you then mix
the
> lime
> putty with sand to get 'coarse stuff', which behaves exactly like mortar.
It behaves similarly but mixed correctly lime mortar for pointing feels
different to Portland mortar - more 'fatty' for want of a better word.
ihate...@gmail.com
I will poke out some pointing I did about 4 weeks ago and see if that
is any better. What worried me was that the lump/pointing turned to
dust, i.e no moisture and therefore couldnt set any more. Now know that
it is more a reaction with the air rather than "drying" I am not quite
as worried as I was.
I'll keep you all informed of my findings with the older pointing.
Thanks again for the replies.
James
andrewpreece
<bi...@biffvernon.freeserve.co.uk> wrote in message
news:1120765441.9...@g44g2000cwa.googlegroups.com...
To take an extreme, if you go to a mix of 100% lime putty and no sand,
then you run into bad shrinkage problems. I know this because in my
early days of experimenting with lime, I mixed up some lime putty and
spread it straight onto a wall as a thin skim. It ended up looking like a
cracked dryed up lake bed! Had to chip it all off :-(
I agree with a previous poster about lime mortar being suitable for pointing
due to its 'fatty' consistency ( best if you soak the lime for weeks in a
closed
container with a layer of water covering it if you want the full 'fatty'
effect, I'm told ). Lime is added to cement mortar as a plasticiser
sometimes
in a 1:1:6 lime/cement/sand mix. If you don't add the lime I believe it's
necessary
to add either PVA or a proprietary plasticiser solution to get the cement
mortar to
handle well. I have been guilty in the past of mixing up mortar consisting
of
1:4 cement/sharp sand, with no plasticiser at all and found that the sharp
sand
and lack of plasticiser combination makes it hard to position bricks or
slabs
well as you often run out of movement in the mortar before you have the
brick
tapped exactly into place. There's nothing to do then but start that brick
all over
again.
More information than you require though!
Andy.
Ian Stirling
> Stuart, your comment about Taliban is in extremely bad taste. Please
> try to learn about lime mortars instead of attempting to be insulting.
>
> BigWallap, you wouldn't want an equal lime sand mix. There should be
> just enough, but no more, lime to fill the spaces between the sand
> grains. This is a bit tricky to work out because it depends on the
> size of sand grains and, especially, whether the sand grains are all
Isn't it simply worked out by taking a bucket of dry sand, and working out
how much water it takes to make it completely sodden, without any sitting
on the top?
bi...@biffvernon.freeserve.co.uk
Ian Stirling wrote:
> Isn't it simply worked out by taking a bucket of dry sand, and working out
> how much water it takes to make it completely sodden, without any sitting
> on the top?
Yes - the tricky bit comes from the fact that it was raining on your
heap of sand and you don't have a measuring jug. :-)
The best lime is the 'lime putty' that is bought from specialist
suppliers, wet, in a plastic tub. This does set pretty quickly. For
best results make sure that the bricks a wet and keep the work damp
with plastic sheeting or wet sacking if the weather is hot. Don't do
it in the winter. Frosts will damage the mortar if they occur before
it is thoughly set and this takes many weeks.
If you use dry bagged hydrated lime - the stuff available at any
builders' merchants, there is a risk that some of it will already have
carbonated. Buy from a merchant with a rapid turnover and when you get
it home empty it into a plastic dustbin of water. Once it is under
water it will be safe from furter reaction and can be kept as long as
you like. When you come to use it tip off the surplus water and scoop
out the resulting lime putty to use with your aggregate. You probably
won't need any extra water. Just keep mixing till it goes smooth.
Mixing a little lime with a Portland cement mortar may make life easier
for the brickie but is usually a BAD idea, despite being a common
practice throughout the building trade. There really is no need to use
cement in domestic buildings.
Andy Luckman (AJL Electronics)
<URL:mailto:bi...@biffvernon.freeserve.co.uk> wrote:
> Stuart, your comment about Taliban is in extremely bad taste. Please
> try to learn about lime mortars instead of attempting to be insulting.
Would you please include some context with your replies?
--
AJL Electronics (G6FGO) Ltd : Satellite and TV aerial systems
http://www.classicmicrocars.co.uk : http://www.ajlelectronics.co.uk
** Would you like to learn to post effectively? **
** http://www.allmyfaqs.com/faq.pl?How_to_post **
Stuart Noble
> Mixing a little lime with a Portland cement mortar may make life easier
> for the brickie
I don't think brickies use lime. Building sand produces a fatty enough
mix without plasticisers. It's plasterers that use it to make sharp sand
renders more workeable.
> There really is no need to use
> cement in domestic buildings.
What, ever? Is cement now banned totally?
Andrew Gabriel
Stuart Noble <stuart_no...@ntlworld.com> writes:
>
>> Mixing a little lime with a Portland cement mortar may make life easier
>> for the brickie
>
> I don't think brickies use lime. Building sand produces a fatty enough
> mix without plasticisers. It's plasterers that use it to make sharp sand
> renders more workeable.
The company which replaced my windows employed a bricky, as one
of the windows was to be reduced in size. He used lime mortar,
without any prompting from me (it is a lime mortar house).
He was quite a young chap too, so I must assume use of lime
mortar is not just an old bricky skill.
He did a very nice job of it too.
--
Andrew Gabriel
Stuart Noble
> Stuart, your comment about Taliban is in extremely bad taste.
Sorry, I just couldn't think of a better way to describe a bigoted,
jumped up little twat who rants and raves about his pet obsession and
would like to make any deviation from it a criminal offence.
> Please
> try to learn about lime mortars instead of attempting to be insulting.
Please try to refrain from being patronising. I have *succeeded* in
being insulting.
> There should be
> just enough, but no more, lime to fill the spaces between the sand
> grains. This is a bit tricky to work out because it depends on the
> size of sand grains and, especially, whether the sand grains are all
> the same size or have a range of grain sizes.
Easy. You just get a sand specification sheet from your builders
merchant stating the number of grain sizes and the number of each type
delivered, broken grains being separately listed of course. The delivery
driver should be able to help. Hard hat (or miter) required though.
> In practice you won't be
> far from the ideal with a 3:1 sand:lime mix for mortar.
Well, why not say that in the first place then?
big...@meeow.co.uk
> I'll take that as a don't know then?
I'll take that as meaning you really are a match for IMM. Maybe the 2
of you'll end up married.
NT
Rod
$WW5...@newsfe6-win.ntli.net:
>
>> Mixing a little lime with a Portland cement mortar may make life easier
>> for the brickie
>
> I don't think brickies use lime. Building sand produces a fatty enough
> mix without plasticisers. It's plasterers that use it to make sharp sand
> renders more workeable.
Ah - so that explains why all the cement that I have bought in the last
couple of years has plasticiser already added by the manufacturer?
--
Rod
Stuart Noble
Just answer the question. How does keeping lime mortar damp hasten its set?
Rob Morley
Noble" stuart_no...@ntlworld.com says...
which reacts with calcium hydroxide to form calcium carbonate.
Stuart Noble
Well, thank you for the explanation.
So the water in the mix is not sufficient to convert the surface layer
to chalk then? Presumably the thicker the layer of mortar, the longer
moisture would be migrating to the surface, which might explain why IME
it is not effective on shallow re-pointing.
As it happens I found myself standing next to a Victorian wall last
night where various types of re-pointing had been done at different
times. What I think was lime I could just about get crumbs from with my
bare finger but it was certainly sound and well adhered to the bricks.
Mike
"Stuart Noble" <stuart_no...@ntlworld.com> wrote in message
news:UkTze.5538$GV6....@newsfe7-win.ntli.net...
> Just answer the question. How does keeping lime mortar damp hasten its
set?
Okay. Lime mortar sets by absorption of CO2 from the atmosphere. Once set
is becomes difficult for CO2 to permeate through it so it must get the CO2
from the other side - i.e. through the wall. This will happen but is slow.
Also once set lime mortar actually shrinks a little and the problem is that
if this happens just on the surface it cracks.
So over several millenia since Roman times, the established practice for
pointing using lime mortar has been to keep the pointing damp using wet
sacking for several months so that it sets evenly throughout the whole width
of the wall.
Does this answer your question ?
Stuart Noble
you would with concrete on a hot day, to ensure a better quality overall
set.
Keeping a wall covered in sacks for several months is all well and good
but how practical is it in this day and age? And how many people realise
this when they buy their tubs of lime putty?
Is it worth going through all that hassle to end up with a mixture of
chalk and sand which does not accommodate movement any more than cement.
The self healing aspect whereby cracks miraculously re-seal themselves
when the surface gets wet is wishful thinking imo because, once
carbonated, the mortar is no longer re-wettable. Chalk cracks, cement
cracks and falls out. Either way I don't see how, in the case of
re-pointing, all this hysteria about lime is justified.
I still think modern additives could be capable of modifying cement to
get the best of both worlds but zealots are not interested in discussing
that.
Stuart Noble
Mike
> >>Just answer the question. How does keeping lime mortar damp hasten its
> > set?
> >
> > Okay. Lime mortar sets by absorption of CO2 from the atmosphere. Once
set
> > is becomes difficult for CO2 to permeate through it so it must get the
CO2
> > from the other side - i.e. through the wall. This will happen but is
slow.
> >
> > Also once set lime mortar actually shrinks a little and the problem is
that
> > if this happens just on the surface it cracks.
> >
> > So over several millenia since Roman times, the established practice for
> > pointing using lime mortar has been to keep the pointing damp using wet
> > sacking for several months so that it sets evenly throughout the whole
width
> > of the wall.
> >
> > Does this answer your question ?
> >
> >
> >
> Sort of, except that you are effectively *retarding* the set, much as
> you would with concrete on a hot day, to ensure a better quality overall
> set.
> Keeping a wall covered in sacks for several months is all well and good
> but how practical is it in this day and age?
Well I've been managing it for three years. It sort of goes with the task
of restoring a historic building.
> And how many people realise this when they buy their tubs of lime putty?
:-) You do after the first wall cracks badly and you then decide to ask the
experts.
> Is it worth going through all that hassle to end up with a mixture of
> chalk and sand which does not accommodate movement any more than cement.
> The self healing aspect whereby cracks miraculously re-seal themselves
> when the surface gets wet is wishful thinking imo because, once
> carbonated, the mortar is no longer re-wettable.
This assumes all the lime is carbonated. That takes about 100 years or
more. Once this happens, as it had on my 200+ year old property, it is
indeed time to rake it out and start again. But on an old building without
deep foundations you have to assume the building will move a lot and lime
does adapt far better than cement.
> Chalk cracks, cement
> cracks and falls out. Either way I don't see how, in the case of
> re-pointing, all this hysteria about lime is justified.
For many people it isn't hysteria, it's the law.
> I still think modern additives could be capable of modifying cement to
> get the best of both worlds but zealots are not interested in discussing
> that.
On the contrary. I've been mixing old and modern methods, looking for the
best of both to restore my house. For instance using lime mortar on a
chimney stack above roof level is senseless as the stack will only be
supporting its own weight and has no need to be flexible. Portland cement
will hold it far more rigidly and protect it from the weather more. One up
for modern techniques.
Conversely the previous occupier had poured a Portland cement concrete
floort which had both failed due to damp building up below but far worse had
pushed most of the damp into the walls where carious containment bodges had
failed one by one. Ripping the whole lot out and replacing with a poured
limecrete floor and some ventilation has resulted in dry floors and walls.
Old technique wins.
What I will agree with you totally though is the zealot thing which gives
restoration a bad name. English Heritage is quite bad but bodies like SPAB
are far worse and unfortunately a lot of conservation officers seem to take
their word as law. As a result some of our listed buildings are being
forced to use totally unsatisfactory techniques just because they are
'authentic'. IMO the only rule for all buildings should be to use to best
available technique.
Stuart Noble
>>Is it worth going through all that hassle to end up with a mixture of
>>chalk and sand which does not accommodate movement any more than cement.
>>The self healing aspect whereby cracks miraculously re-seal themselves
>>when the surface gets wet is wishful thinking imo because, once
>>carbonated, the mortar is no longer re-wettable.
>
>
> This assumes all the lime is carbonated. That takes about 100 years or
> more. Once this happens, as it had on my 200+ year old property, it is
> indeed time to rake it out and start again.
So the longer the lime remains uncarbonated the better then? Assuming a
reasonable depth of mortar, it would actually be more water resistant if
the bulk could be prevented from carbonating.
> On the contrary. I've been mixing old and modern methods, looking for the
> best of both to restore my house. For instance using lime mortar on a
> chimney stack above roof level is senseless as the stack will only be
> supporting its own weight and has no need to be flexible. Portland cement
> will hold it far more rigidly and protect it from the weather more. One up
> for modern techniques.
Hm. I can see some flack coming your way....
I was kind of thinking about even more modern innovations. Plasticisers,
polymers etc. SBR produces a slightly rubberised mortar, which sounds
horrible but doesn't affect the texture or the appearance at all. It's
the basis of latex floor screed but I'm sure there are other
applications for it.
>
> What I will agree with you totally though is the zealot thing which gives
> restoration a bad name. English Heritage is quite bad but bodies like SPAB
> are far worse and unfortunately a lot of conservation officers seem to take
> their word as law. As a result some of our listed buildings are being
> forced to use totally unsatisfactory techniques just because they are
> 'authentic'. IMO the only rule for all buildings should be to use to best
> available technique.
And to keep things in perspective. Houses are for people to live in, so
either compromise on the restoration standards or knock the bloody place
down. I know of one such edifice that is visited by people with
clipboards now and again, and hopefully it will eventually fall on them
rather than the family who live next door to it. Shame, because it is
(was) a superb example of a small industrial building. It is, however,
quite near the Olympic Village site so maybe there will be some money
for a quick Victorian makeover.
Hamie
He appears to be in the minority then... I had arguments with abricky
(Who told my wife to shut up & that she didn't know what she was talking
about. Unfortunately when I wasn't present) when he insisted that Lime
Mortar was sand/cement/lime. And that you HAD to have cement in it.
Needless to say the company didn't get to finish my conversion... Sadly
they're still in business.
big...@meeow.co.uk
> He appears to be in the minority then... I had arguments with abricky
> (Who told my wife to shut up & that she didn't know what she was talking
> about. Unfortunately when I wasn't present) when he insisted that Lime
> Mortar was sand/cement/lime. And that you HAD to have cement in it.
People who dont know to be more careful often get cement and lime
wrongly described as 'lime mortar.' The other common problem is they
add 5% cement when youre not looking to make it go off quick. Beware of
builders bearing cement.
NT
ihate...@gmail.com
Something I didnt mention in the original post (sorry), the reason I
was raking out the new lime pointing was that it was very white on the
surface. ( I hadnt buffed it when I should)
My supplier said that this is lime and has been brought to the surface
by the lime drying too quickly. Leaving too little lime "in the mix" to
harden everything nicely. Now I did wet down the joints, but I and
going to do moreso in my next attempt. The pointing I have done
previously which isnt white, (its a nice yellowy colour) has set
nicely.
Ill let you know how it goes!
James
Bob
There are at least three types of lime and it can be confusing.
1 Hydrated Lime - easy to get, used as an additive to cement, useless for lime
pointing.
2 Lime Putty - does not set when kept wet, no use for foundations.
3 Natural Hydraulic Lime - does set when wet and comes in three strengths NHL
2, NHL 3.5 and NHL 5.
best in my opinion for all lime work. see
http://www.lime-mortars.co.uk/articles/hydraulic-lime-which-nhl
--
for full context, visit http://www.homeownershub.com/uk-diy/crumbling-new-lime-mortar-pointing-732335-.htm
harry
> big...@meeow.co.uk wrote:
>
> > For the OP, lime mortar should idally be kept damp for a few weeks to
> > hasten its set. It can be covered with sheeting, or sprinkled.
> >
> How would keeping it damp hasten its cure? I think you cover it until
> the surface has cured/carbonated/dried sufficiently to withstand rain.
> Not exactly a practical proposition, which is presumably why hydraulic
> lime was used. Maybe the sand also has a pozzolan effect. How would you
> ever get a house built otherwise?
Outside walls have to be covered to aid drying and stop rain leeching the lime out.
harry
The scaffolding has been up for months and the whole tower wrapped in woven plastic.
Must be costing a fortune.
DICEGEORGE
by Jane Schofield (Author)
A practical guide to the use of lime for repairing and redecorating old buildings. Suitable for homeowners, builders or even interested professionals who are unsure where to start or what to do. It contains basic, simple recipes with easy rule-of-thumb measures and advice on preparation, techniques and materials. There is an up-to-date suppliers list.
https://www.amazon.co.uk/Lime-Building-Practical-Jane-Schofield/dp/0952434121
I bought a copy years ago from soewhere, amazon seems a trifle expensive
[george]
DICEGEORGE
[g]
Adam Aglionby
https://constructionweek2012.files.wordpress.com/2012/09/a-practical-guide-on-lime-in-building.pdf
http://www.buildinglimesforum.org.uk/
Some Councils offer useful advice shock:
https://www.southsomerset.gov.uk/media/410713/lime_book_2010_revised_draft.pdf
http://www.shetland.gov.uk/planningcontrol/advicenotes/documents/AdviceNote13-LimeMortarsandRenders_000.pdf
Am now incumbent of 1869 , ex railway, building that has been previously had some well intentioned , but wrong, re pointing done in cement.
Haven`t seen Stuart here in a while, but can assure him that repointing a rock faced stone building with cement is liable to blow the front of the stone off with frost.
The areas with open pointing have actually survived better.
Any tips on cutting cement out of the joins?
tabb...@gmail.com
NT