That's rather a blanket statement Biff. I don't think you have demonstrated that Steve's 'old tradesman type builder' is wrong, or indeed what he is wrong about, you merely hint that he is.

I also think anyone can be lured in by respect for either tradesmen, builders or indeed wholesalers and manufacturers. In this day and age it seems everyone wants to be seen to be green - whether they are or are not. Clearly some are very knowledgable and/or genuine, some are not - same in all walks of life.

When I try to guage these things - I often ask myself who has the most to gain by distorting or ignoring the issues at hand.

But the fact is, Jon, that the use of lime mortar involves less CO2 emmision to the atmosphere than OPC mortar. What justification are you looking for?

Mike, of course mine was a 'blnket statement'. I don't know this particular tradesman or the circumstances for which he was advocating 7:1 sand:OPC, but it is entirely possible that his views are wrong.

Perhaps we have a Green Building Forum because we think that much of the practice of the building industry is very wrong.

Sorry Jon but I can't see your problem. At the risk of repetition, there are two main sources of CO2 in both lime and cement production. The fuel used in kilning and the CO2 evolved in the CaCO3 to CaO2 reaction. Lime kilning requires a lower temperature therefore less fuel therefore less CO2. With lime the CO2 evolved in the reaction is all reabsorbed from the atmosphere on setting so there is no net addition to the air, while cement sets by silicification which does not reabsorb significant amounts of the CO2.

So, all other things being equal, lime results in less CO2 going into the atmosphere than OPC. If you want to know the numbers that last link I posted tells you how to do the arithmetic. Of course all other things may not be equal - you may be air-freighting your lime from New Zealand.

Of course there are loads of other reasons why lime is a much better building material (except for airport runways, motorway bridges, multi-storey carparks and nuclear power stations, but we don't need any of them do we?). So that just leaves the foundations of wind turbines.

Eh? Once all the carbonation is complete, there is no further CO2 contribution, whether the lime or OPC lasts in the building for ten years or a thousand.

If you are talking about more than whole life, using lime to stick the bricks together means that when the building is pulled down the mortar can be knocked off easily and the bricks reused. With OPC you just get a heap of broken bricks and have to fire new ones at further fuel/CO2 cost. Just one of the many advantages of lime.

"ethically justifiable argument"...explain please?

Hi Ludite, A widely accepted mix using a combination of Lime: Cement: Sand is 1:1:5. The older mix most likely contained no cement at all, the lime being mixed with some common aggregate in your area. In South Wales, they used a lot of ash resulting in what we locally call 'black mortar'

Do you mean I could have just used 2 scoops of lime and 5 of sand and forgotten all about the cement?

Ah, now we have it. Brickies can build faster with OPC than with lime. That's the ONLY advantage, and it's no advantage at all because it just allows the chuck-em-up-quick developers to build rubbish houses.

Jon, you are going to have to put it in even more simple terms for the likes of me. Are you suggesting that a lime built house will not last as long as an OPC one? If so, 'tis nonsense.

I would not let my children anywhere near powdered lime -it is not something you want to breath in. Cement is not nice in this respect either, though it is not as fine, meaning it is not quite as bad.

Both cement and lime are also irritants, so not to be played with when wet either, again, I think Lime is worse. Get some in a cut and you will know all about it - for days afterwards - burns like hell.

Hydrated lime is really caustic stuff, its such a fine powder that it hangs in the air quite a long time, I always promise myself i'm going to wear a mask the next time i mix up and then usually I don't. but I should. also, ordinary hydrated lime-not the french hydraulic stuff- is better mixed a couple of days before it is used. very dangerous to breathe. and if used without gloves, will tend to make little holes in your hands over a couple of days.

Thanks for the health and safety info. I thought it was bad stuff. I'll use up what I have left when the kids are out of the way.

The trouble with Kids is they don't have any fear, Its all very well tellung them to wear gloves, what happens when they start to throw the stuff around? or taste it? or scratch their little bottoms with their limey covered hands.

I have young children - and I wouldn't let them anywhere near it.

There is no way that I would ever let young children near cement, come to that. The chromium salts and other things in it react worse with my skin than lime, and my hands are like leather. I use lime every day, and take the usual precautions, but on the very rare occasions I use cement I find that even a small amount on the skin causes dryness, splitting and irritation very quickly. It's nasty stuff. OPC in the eyes - or anywhere else sensitive - is just as damaging as lime. If you want your kids to play at building, just give them wet sand. Keep them away from anything else.

As for longevity, surely the fact that buildings made with lime mortar are still standing after several hundred years is rather more than hearsay.

Raising children involves introducing them to hazards, crossing the road, riding a bike, rock climbing, and even bricklaying, in an appropriate manner. I no longer have young children. All four of them grew old.

Jon, take a look at 200 year old buildings. The surviving ones are all built with lime rather than OPC.

:)

My 2 are little. I want to introduce them to all sorts of stuff, but my main goal is to go to my grave knowing that they still have all their fingers, toes, eyes - and all their other bits and pieces. Unfortunately, I'm a bit cavalier when it comes to using stuff myself. I have used Lime, OPC, formaldehyde, caustic soda, excessive heat and probably lots of other stuff over the years - but what you do to yourself is different to what you allow your kids to do - until they can make up their own minds.

Never for residential use if you're an idealist - on the other hand try getting your BCO to agree! And if you figured out how, do let me know!