Is lime mortar required?

26 Feb 2017
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United Kingdom
Hi, even though large swathes of the UK are victorian built houses. I'm finding it hard to find suitable lime mortar at B&Q, Wickes etc for my victorian mid terrace to do some pointing. Why don't the major chains stock lime mortar? Do people not both and just use portland cement mixed mortar?

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You can get bags of hydrated lime from builders merchants. Often s&c mortar is used, or you can use some hydrated lime in it. As opposed to hydraulic which comes in a tub and is more for actual “lime mortar”/“lime plaster” preservation work.
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You might need to take some advice from your local lime suppliers. A lot of people use NHL3.5 for exterior pointing(often use it myself), but it does go off quite hard in time, so for a softer brick they may recommend NHL 2 or even an air lime with a pozzolan.
For pointing you are looking for a similar mix to the original, maybe just a touch weaker.
Use NHL 2 lime for pointing.
Use a 4:1 sand & lime mix with clean water.
In fact, use NH 2 for most residential work - damp proofing renders etc.
Builder's merchants will usually supply bagged NH 2 if you simply ask for "Builder's Lime".
I've always understood that the higher numbers NH 3 etc refer to how quick the mix sets up?
It's easy to get confused:

1) Hydrated lime - also known as bag lime - comes in a sack, used to mix in with cement, not as a mortar in itself (I've never used it)

2) Natural Hydraulic Lime (NHL) comes in a sack. Softer and more flexible than cement, harder and more brittle than lime putty. It's called hydraulic because it sets with water (which lime putty doesn't). The higher the number, the harder (and more brittle) the mortar will be (NHL 2, NHL 3.5, NHL 5) I agree with ted456 - I'd use NHL 2 (or NHL 3.5 if I can't get hold of 2) for repointing

3) Lime putty - comes in tub as a wet putty - keeps for ever if wet (gets better the longer you keep it). Lovely stuff to work with, especially if you're a slow amateur plasterer like me

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