Lime: bagged versus putty

[Anonymous]

I just want to raise a few points about limes, in the hope of seeing what your thoughts are.

I have been repointing a rubble cottage recently, partly using lime putty, and partly using bagged hydrated lime. Now, I realise that lime putty is undoubtedly the better material, and if used properly will guarantee good results. However, my experience is that for my purposes, hydrated lime has produced identical-looking and performing mortar to the putty. This is despite me simplifying things to the minimum by mixing it dry with sand and then water rather than soaking first to produce a putty. And hydrated lime is much cheaper than lime putty. It also avoids the problem of sloppy mortar which one tends to get occasionally when putty is used, even when no extra water is added.

I do not use bagged lime for plastering, and I would not use it if I was repointing Windsor Castle. However, I do feel that by insisting on the use of lime putty on all occasions, the conservation movement is sometimes making the best the enemy of the good. My contention is that the average builder, doing the average repointing job, is much more likely to switch from OPC to bagged lime, which is cheap and can be mixed in the same way as cement mortar, than he is to switch to putty, which is expensive, not available at builders merchants, and of alien appearance.

Any thoughts?

 

[Anonymous]

I agree.

And furthermore, I was doing some lime morter work With bagged hydrated lime, a few weeks ago and had half a bucket left over. So I stuck it of a wattle hurdle that I'm planning to plaster when the weather warms up, thinking it will probably crumble and need doing if the frost gets to it. The temperature got down to minus 4 the next night. But it's fine. <IMG SRC="http://www.periodproperty.co.uk/discussing/smileys/smile.gif" BORDER=0 ALT="">

 

[Anonymous]

Please correct previous post using these words 'mortar' and 'on' and 'again' as appropriate.

 

[Anonymous]

My thoughts are that you've been reading Jeff Howell and that's about what he said.

Many do disagree of course, and consider that a decent putty is really better, but better bagged lime than cement.

But I'm inclined to leave it to form a putty of sorts for a while rather than mix and use.

 

[Anonymous]

I would have thought that the only real reason that hydrated lime gets bad press is because of the lack of turnover at the merchants. If you buy portland from somewhere like Focus DIY, the chances are it's been there a few weeks and has already gone off.

Buy hydrated from somewhere with a high turnover of hydrated, the chances are it will be fine, otherwise, you just don't know how much of it has carbonated.

 

[Anonymous]

Sometimes I think lime is like wine. Some folk (rich folk) claim that certain vintages from certain vineyards kept for certain periods under certain conditions taste better. Some of us just enjoy what's on special offer at the Coop this week.

But the best wine is always what you find in a little cave up a long track to nowhere on a very hot day and buying it involves a fair bit of arm waving.

 

[Anonymous]

There are tales of mature lime putty being handed down through generations.

 

[Anonymous]

Just like wine then.

 

[Anonymous]

What mix ratio of dry bagged hydrated lime to sand do you recommend for repointing old brickwork?

 

[Anonymous]

hydrated is just as good as putty i have used it for over 10 years with no failure. the only difference is the amount of water added to quicklime in the production process - more water makes a putty, less makes a hydrate - the less water added to quicklime, the better the binding capability. used as a 1:2 mix it will do most jobs and also makes a great limewash (note: the 1:3 mix is based on the historic use of quicklime and aggregat mixed pre slaking - post slaking the lime volume almost doubles.... so; most historic mortar is a 1:1 1/2 - 2 mix not 1:3 .... this is too sandy)cas*le do hydrate in a plastic inner liner now.... so, no carbonation in the bag. why pay more? and yes, lime was passed down the lines of 'stuccodour' familys in italy.

 

[Anonymous]

I have used 1:3 lime to sand very successfully. Make sure you use sharp sand rather than building sand.

I mix them dry (using a cement mixer, but you could do it with a shovel) then add as little water as possible to get a workable mix. I normally keep the mixer going for about 20 minutes as a really thorough mix helps the quality of the mortar. Then I leave it overnight before use, protected by polythene. It will keep indefinitely in an airtight container.