Mixing cement and lime- should I do it?

The houses on my 1990 housing estate where built using calcium silicate house bricks. These bricks did not have a frog and all sided of the brick were flat. Over the years all of the houses have suffered from some cracking of the mortar. Different surveyors called in have suggested a lack of ties, trees and bushes to close to houses and the wrong type of mortar mix. It is nothing too serious and a good eye is needed to spot the cracks.

I am now about to have an extension built and have managed to find some of these bricks but with frogs, as they are the only ones I could find that match. The instructions that came with the bricks state that the mortar mix should be either 1:1:6 or 1:2:9 for Cement : Lime : Sand. Do I need to insist that the builder adds lime as I have read the following post on another thread here about cement?

Re adding lime to cement mortars, this doesn't give any of the properties of a lime mortar. Also most lime/cement mixes are liable to fail prematurely, so adding a bit of lime to cement mortar or adding a bit of cement to lime mortar are both not recommended. There has been research done on this.

Reply to
informer
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Mixes with equal quantities of cement and lime work well, e.g. 1:1:6. Most other ratios of cement to lime don't work.

Reply to
Andrew Gabriel

1:1:6 is the one lime:cement mix that works well. 1:2:9 is prone to premature failure.

NT

Reply to
meow2222

Oh? I've done that a lot in a garden wall. Seems to be holding up all right after a couple of winters..mind you I used ties EVERYWHERE..

Nothing will cope with poor foundations however.

Reply to
The Natural Philosopher

Calcium silicate bricks have different properties to traditional clay bricks ( including absorbstion and expansion) and so the manufacturers guidelines should be followed. The NHBC guidelines (and others) specify that the mortar should be as per the manufacturers recommendations.

You are taking that post out of context. Lime can be added to the mix for a number of reasons, and this does not meant the mortar will "fail prematurely" - whatever that is supposed to mean?

Mortar cracks for a number of reasons too, and this does not necesarily indicate a problem. A weaker mix (with or without lime) will accomodate movement more if movement is expected. A strong mix will be less flexible but perhaps will minimise movement. Its all about horses for courses. In either case, it is the pointing to the joint that provides the weathering properties and longetivity of the mortar, and this is separate to the strength of the mortar.

You should insist that the builder uses the recommended mortar mix.

dg

Reply to
dg

1.1.6. is a fairly standard mix and should be fine. The lime makes the cement mix sticky and easier to work with. The Romans built their coliseum with it so your extension should be ok.
Reply to
noelogara

Obviously prone to premature failure doesnt mean 100% will fail within

2 years. Google should turn up the research if youre interested.

Lime mortar seems to have coped well enough with millions of houses with poor foundations so far.

NT

Reply to
meow2222

And *failed* on tens of millions that simply aren't there anymore to prove my point ;-)

Reply to
The Natural Philosopher

I find it hard to believe that millions of houses have been demolished because someone couldnt be arsed to repoint them. Can you support what you say somehow?

NT

Reply to
meow2222

I believe the figure is something like 1 in 6 Victorian houses remain today, but most were demolished for social reasons as part of various slum clearance programmes, not structural problems.

Reply to
Andrew Gabriel

Quite so. I'm surprised if its as few as 1 in 6, that would add up to a whole lot of houses then. Also bear in mind with these figures that what we have left is primarily the middle class housing, the shacks are all gone, and we wouldnt really call those houses today.

NT

Reply to
meow2222

You're not an estate agent then? Lots of those 'shacks' still survive round here and sell for £300K ... when you could buy a much more spacious

1930's semi with garden and parking for less.
Reply to
Tony Bryer

Who is talking about repointing?

Show me ONE place apart from your last comment, where any of the previous refers to pointing.

Its always a sign of someone with an axe to grind when they change the subject to appear to be more likely to win it.

Reply to
The Natural Philosopher

I don't think you can separate crumbling damp leaking housing from "social reasons".

Building regulations are in essence socially inspired.

Reply to
The Natural Philosopher

I would be surprised if its as great as 1 in 20.

Mind you, by that time they had portland cement..prior to that its a lot less ;-)

Reply to
The Natural Philosopher

You are joking right? You want to see what a Victorian 'shack' is really like - well basically you can't, because they were all (rightfully IMHO) condemned years ago..I did stumble across a derelict one once though. Wasn't really safe to go inside..Think two caravans on top of eahcother with a crumbling brick chimnney up the middle, and that was about the size of it, except subtract any insulation, heating apart from a coal fire and a coal range, water, gas, electricity or sewage facilities, and thats what it was.

A semi-permanent tent made with a few bricks, crumbly lime mortar and whatever bits of wood someone could find, plastered over with cowdung, horse hair and lime, and probably covered in rushes. Needless to say te lime mortar had failed, and only half the chimney was left..mostly the inside bit out of the weather..all te wioodwirk was rotten - most of the upper storey was in the lower - and most of the roof had gone, due to failure of first the thatch, and subsequently the corrugated iron sheets that had been nailed over.

If it had been within range of a decent water supply, or a road, the site alone was probably worth a couople of hundred though, with planning permission..

There was another one close by, but that was simply a mound of bramble infested rubble covered in grass and scrub. It just fell down. Good stuff lime mortar. Always has plenty of 'give' in it. ;-)

Reply to
The Natural Philosopher

I dont see how a shack would be considered fit for habitation nowadays. Theyre very rare in Britain because theyre not even legal, and havent been for a long time. Our fussy government wants stuff like water, drainage, bath, loo, windows, that sort of thing.

NT

Reply to
meow2222

Why does a brick house crumble? Because no-one is willing to spend a small amount to maintain it. Ditto with damp and leaks. Thats social, and will happen to any unvalued building regardless of its construction or utility. Most demolished buildings have not crumbled anyway. They were just in the way of roads, shopping malls, or bigger houses. Or were poorly maintained and the government them wanted shifted so the place looked nicer.

NT

Reply to
meow2222

huh??

Reply to
meow2222

Because its badly deigned and built.

< Ditto with damp and leaks.

Indeed :-)

Indeed. I was not talking of demolished buildings, just the ones that fell down all by themselves.

Reply to
The Natural Philosopher

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