Lime mortar

[lurker]

My house was built around 1937 and the mortar used was a traditional lime mortar, I assume.
The joints have been re pointed with Portland cement and inevitably its falling away.
What I want to do is gradually sort out the bad bits and was planning to use traditional lime. There are lots of recipes on the internet but I have greater trust of folks here.
So.. anyone with any experience and a tried and trusted way of making it?
I guess I would use a heap about the size of a bag of sugar at a time( I have a low boredom threshold ) .
I have "garden lime" (is this OK?) and will probably "experiment" with sand colours to get the shade I want.
I understand its works best when you let it "age" for a few weeks in an airtight bucket.
Would a PVA placticiser be any improvement to a traditional mix?

 

[Selwyn]

Buy lime putty and mix with sharp sand 4 to 1

 

[topchippyles]

Google ty mawr lime and it will give you all the info required

 

[Beau]

Dont think there is one perfect answer.

What mix you use is dictated by the hardness of the stone/brick, aggregates used, NHL brand and how exposed the wall is. I used an NHL 3.5 lime for our barn but this was on uneven stone with big gaps to fill. Find a supplier you like the look of and take their advise would be my suggestion.

 

[MikeG.]

Just to chuck a minor spanner in the works.......much lime mortar wasn't made with sand. It was often mixed with chalk. This produces quite a different mortar to sand. My cottage used sand & lime for the very bottom course only, and everything above that was lime & chalk. Ty Mawr or Anglia Lime will be able to advise, but take a good look at what you've got first.

 

[lurker]

Thanks Mike

The mortar between the courses is sand I am sure.
In bad places it looks like no more than compacted yellow sand.

 

[Doug71]

You can send a sample of your mortar off to be tested and they will tell you what is in it.

A friend of mine re pointed his barn in lime mortar. It came ready mixed in sealed buckets, it was probably an expensive way to do it but it kept for ages, he could just drop on it and do a bit whenever he got chance and he knew it would be a consistent mix.

I was working on a barn conversion a while ago where the ridges and valleys were pointed with lime mortar and it was just washing out. The gutters and no doubt the drains were full of it, guess they had got the wrong mix.

 

[lurker]

I did acquire some of this stuff, but it is far too gritty for pointing a brick wall. it would be perfect for a stone wall however.

I am going to experiment with lime and sand.
As advised will not use PVA.

 

[Paul200]

Found these people incredibly helpful when we bricked up a window on our 1920's built bungalow in Somerset and wanted to match into the existing lime mortar.

https://www.limebase.co.uk/

Don't know where you're based lurker, but the website alone has masses of information that may be of use.

Cheers

Paul