Lime or cement mortar?

Lime or cement mortar?
This is specific to old buildings, and walls of similar construction. These houses typically use soft bricks that break easily, often have little in the way of foundations, sometimes none, and most have no dpc.
Movement --------
Skimpy foundations mean minor movement is a normal event for many old houses.
Cement is not movement friendly, and with any wall movement cement typically makes a single clean break. It has no self healing ability. Normal wall movement thus results in broken walls, which compromise the overall house structure, and require extra repair work.
Cement mortar is stronger than soft brick, so when movement occurs it is the bricks that will break rather than the cement. Broken bricks have their core exposed, and without the protection of the fireskin these bricks will usually begin to slowly deteriorate due to wet freeze cycles. Gradual erosion of the brick leaves the wall in need of many bricks being replaced. Its a shame to see walls like this, knowing that just a little more knowledge and no damage would have occurred. Theres a building near here that has about half the bricks near ground level badly decayed, and is now in need of large numbers of bricks replaced.
Lime mortar is weaker than the soft bricks, so when movement occurs it is the lime that cracks, not the bricks. This is the better option. No bricks need replacement.
When moved to breaking point, instead of forming a single break, lime tends to form lots of microcracks. Lime then reacts with the CO2 in the air to grow hard crystals across these microcracks, and thus rebonds itself. It self-heals. Lime mortar is not flexible, but it behaves as if it were in this way. Lime accomodates normal minor movement without incident.
Damp
--

Old houses handle damp differently to new builds. Soft bricks are
porous, and rain hitting them soaks in a little. Interior condensation
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Congrats on a cracking post :-)
PS: any ideas whether lime mortar is suitable for repointing a cemented wall ?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Colin Wilson wrote:

You can use it but it isn't as likely to stay in place.
The colour of the sand used in cement mortar controls the colour of the mortar and the strength of the mix controls the damage it is likely to do.
If using soft bricks you would use an eight to one mix -which at the price given in the OP (and the quantities of lime needed as three to one) makes it a far cheaper alternative. It is with the overall concern of the project and the consumer's tastes that the costs may seem small.
It isn't in the same category for example as the price of a new car compared to a three year old one. You can of course use any inert admixture to either sand or cement to make mortar. And you can get a pleasant effect with different sands if shortly after the bricks are pointed, the wall is washed.
Maching it all the way through the different courses would require some skill though. Too many would-be bricklayers can't even put a wall up without a great variety of shade in the allegedly same mix.
Errors to watch out for are bricks laid upside down and the poor selection of bricks by the labourer. Each course must be laid with a few bricks from each pallet to prevent the differences in batches showing up.
Also a load of bricks should never be tipped out of a lorry. This isn't so much a problem these days with most lorries transporting them having grabs.
Too frequently the developer will not have all the bricks for an house delivered on site in one or two loads. Often this is a space or security limitation.
And these days most labourers have little or no training, with bricklayers on pricework not caring nor being paid to point out tips in such craftsmanship.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 10 Aug 2006 17:19:13 -0700, snipped-for-privacy@care2.com wrote:
|Lime or cement mortar?
This post deserves a place in the FAQs Maybe after those who understand the problem have discussed it.
--
Dave Fawthrop <dave hyphenologist co uk> Google Groups is IME the *worst*
method of accessing usenet. GG subscribers would be well advised get a
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Tiptop post on lime - and very much my practice.
My process for small quantities of lime putty - buy a new plastic dustbin with tight fitting lid, half fill with water, empty a bag of hydrated (builders) lime into it, leave for as long as possible (ideally months).
I make up lime mortar when needed, half fill bucket with SHARP sand, add a third more to the volume of lime putty by eye - mix with paddle attachment on big drill, then keep bucket in binbag for ready supply- as you say, it keeps so long as it's wet.
Might be worth saying a bit about mixing - as lime mortar is so senstive to water content - the difference between a stiff mixture and soup may be half a cup of water in a bucket. Often the moisture in the sand plus the lime putty is just about the right water content - but if the sand is a bit dry, getting that easy to work with softish butter may take a little added water - go very gently to avoid ending up with soup!
Would the OP like to add a bit about using hydraulic lime?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@care2.com wrote:

Yeah, lime is so bloody marvellous that when they built the London sewer they scraped it entirely in favour of Portland cement, which has stood the test of time underground in the damp.
I won;t bother to go through pickling out the things that are plain wrong, and those that are simply exaggerated through prejudice.
Suffice to say there are good reasons why Portland cement is used rather than lime, these days.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The Natural Philosopher wrote:

The great advantage of portland cement is that it undergoes a very predictable/repeatable chemical set, and it's fast - making it more suitable for modern site bricklaying practice. For the same reasons large quantities of concrete can be cast with highly consistent properties.

Oh please do.

Any others than the 2 I've mentioned above?
For the DIY'er with a slower work rate on buildings originally constructed with lime mortar, there really isn't a downside. It's easier to use, it can be kept indefinitely and it's better for the building - and especially with soft bricks or limestone, it's a necessity.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The Natural Philosopher wrote:

PLEASE do. Most of the OP seemed very reasonable to me, but I would love to hear opposing views. (I have to say that the paens of praise for the visual appearance of lime mortar struck me as over-egging the pudding).

To be fair, the OP did start:

With a new build, hard-fired bricks, DPC, and extensive foundations, a lot of the arguments for lime go away.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Martin Bonner wrote:

As someone has already said, there is no mention of hydraulic lime. For example, brick dust acts as a pozzolan (as does any material that has previously been baked, volcanic ash, iron oxide dyes etc.) and this causes the mortar to set in varying degrees. This aspect seems to be shrouded in mystery (I suspect deliberately). How much of the alleged self healing property is lost, and how does it then differ from cement? I doubt the Victorians could build houses at the rate they did without some form of set taking place.
IME, if you can't protect ordinary lime mortar from the weather, shallow applications such as pointing will be washed away by the first rainfall. Hanging damp sacks all over the place doesn't seem that practical to me.
The other issue is the degree to which modern additives have improved the properties of cement. At a basic level I'm sure we're all familiar with how pva reduces cracking and doubtless there are more sophisticated products around.
There is of course a large element of brown eggs and bicycles about all this too. Right on types who want to turn the whole thing into an art form and congratulate each other on their good taste via various conservation websites.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Do you mean heavy rain washing out new pointing? The initial set of at least the surface should take a few hours. After that I would be surprised if it washed out to a significant degree with normal rainfall. I have heard at (at a limes seminar) of a heavy section of new/repair lathe and plaster ceiling detaching - as a consequence of poor mix and poor application. Potentially quite dangerous - it does take time (weeks/months) for a thick area of lime mortar/plaster to carbonate right through and gain it's full strength.

I don't think you can get away from the fact that cement pointing will trap moisture and lead to soft bricks spalling. It also acts as a sacraficial material around limestone, so it's the mortar that slowly erodes and not the stones.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 11 Aug,

It can be hundreds of years, I gather a survey was done of the columns in Durham Cathedral some years ago, and some of the Norman mortar in the middle of the columns was not fully cured.
I gather there are two stages to lime setting, the final (very slow) stage being back to the CaCO4 it started off as.
--
B Thumbs
Change lycos to yahoo to reply
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@gglz.com wrote:

My impression is that lime pointing does it worse actually.
Old bricks are soft and porous and crumbly, they need a soft crumbly porous mortar like lime. Modern bricks are not like that.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Stuart Noble wrote:

What a silly post.
The OP was discusing the use of limes as a compound best suited for soft bricks.
As it happens the Romans who were responsible for the building of sewers in the first century, built with concrete materials. I don't know if that came from Pozzolan but it sounds suspiciously like it may have:
Materials which enable lime mortars to set more rapidly include ash and brick dust. Known as 'pozzolans' after the volcanic additives used by the Romans, these materials are widely found in the lime mortars used in old buildings and monuments.
Where conservation work is required, new mortars ought to match these mortars, not only to ensure continuity with the past, but also to ensure that the new work is both visually and physically compatible with the old. It is therefore important that we know more about the performance of these additives.
A simple everyday definition of 'pozzolan' could be 'a finely powdered material which can be added to lime mortar (or to Portland cement mortar) to increase durability and, in the case of lime mortars, to provide a positive set'.
A more formal definition is given by ASTM C618 as 'a siliceous or siliceous and aluminous material which, in itself, possesses little or no cementitious value but which will, in finely divided form in the presence of moisture, react chemically with calcium hydroxide at ordinary temperature to form compounds possessing cementitious properties'.
http://www.buildingconservation.com/articles/pozzo/pozzo.htm
The sewers built in Britain were not built until the Victorian era for precisely that reason. Cement is a far better material to use such places. As the bricks were of the very finest available, capable of withstanding traffic in the world's busiest cities, you can see that they chose well.
As for the Victorians building houses quickly; to build the sewers they removed thousands of squalid hosuese and dug trenches by the mile in which the sewers were laid. They then had gangs upon gangs putting the housing on top of them.
I the eras befor modern planning laws it was very easy to use skilled with semiskilled men to get the most out of both.
Such a situation is recurring these days now that there are no apprentices growing into the trades. But that is a topic for alt.politics.thatcherism.
***
One can use lime mortar in modern facework. Just remember to close the gaps up. If you look at some of the fines examples of redbrick face work still standing after a cetury or so, you may notice that they too used lime mortar but that the distances between bricks are a lot smaller than the present standards.
But the OP was not discussing modern standards you damn fool.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

As usual the OP wasn't *discussing* anything, just delivering another sermon.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

To me that's quite a plus. When repointing, you wait for an initial set, then give it a going over with a stiff brush. Result is an appearance very close to undamaged areas and is very forgiving of skill levels - uniform consistant results for all of us.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Fri, 11 Aug 2006 09:23:33 +0100, The Natural Philosopher wrote:

Indeed and there are good reasons why lime should be used and not Portland cement in some circumstances. It's completely bloody stupid to point, patch or repair brickwork on a property built using lime mortar with Portland cement. It will do more damage than good.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@care2.com writes

Snip excellent post....
I think I'm safe from most of the problems. No expected movement, little evaporation and appearance not really an issue. Currently brick waste is sought for crushing as hardcore: avoids the mineral tax:-) However, I can easily shove an extra ration of hydrated lime to the mix as a half measure.
regards
--
Tim Lamb

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@care2.com wrote:

What's the "chemical cycle" of cement?
What about the production cycle? How much CO2 is released in processing and transporting v. cement?
MBQ
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@hotmail.com wrote:

I don't think the lime cycle is quite carbon neutral - as (fossil fuel derived) heat is put into the kiln. However the CO2 driven off in the kiln should be exactly balanced by that absorbed on the mortar taking its final set. The fossil fuel footprint of transportation is probably equal for cement and lime. I think the larger culprit is using large amounts of concrete in construction - quick,convenient, relatively cheap - and a lot of energy consumed in its manufacture/delivery.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@hotmail.com wrote:

I can't remember the details, but my recollection is that the chemical changes in the production of cement release more CO2 than is taken up during its setting (so there is a net release).

Lime is heated less than cement, so it doesn't take as much fuel to produce.

Lime powder and cement are much of a muchness for transportation. Lime putty of course will be a lot more expensive to transport.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.