Lime mortar repointing project

[iang]

Hi all

I'm new to this so please bear with me.

I'm about to embark on a repointing project on my barn conversion.

The aim is to remove the cement pointing and replace with lime mortar.

It's about 160m2 and I'm working alone.

Would you recommend removing all the pointing first or taking it a section at a time?

It seems cheaper to deliver large quantities of lime rather than lots of smaller amounts.
Is it OK to keep a large quantity of lime (1 tonne) lying around on site as I slowly progress the job or will the product deteriorate
if I take this approach.

Thanks for your help in advance and look forward to more basic questions from me over the next few months.

Ian

 

[Kearn]

Pick off a square meter at a time, chip out, clean, stack and repoint. Save leaving masses exposed for a long time… and it maintains some semblance of sanity!

Lime putty gets better with age, assuming you’re getting pre-mixed tubs / bags. If your thinking of powdered NHL then it’s worth doing some research first into the right materials…

 

[iang]

Thanks Kearn.

A section at a time sounds like a good call.

 

[stuart45]

Blue lias is a lot softer than Chert, so using an angle grinder down the centre of the joints first might help cut down the damage to the stone when you cut out with the chisel.
Limebase are a really good local supplier who are happy to give advice about the correct mortar to use. You can take a mortar sample in to them.

 

[aockenden]

I actually disagree. I think knocking it all off first gives the entire wall longer to dry out in the wind before sealing it back up with Lime. Then when you start repointing, you can start from the first section you removed cement from and work towards the most recently removed areas.

As for the lime storage on-site, it totally depends on the type of lime you’re wanting to use. A slaked putty that is covered in a layer of water will be absolutely fine, and might slightly improve in plasticity and workability (if you believe the old-timers) during the period. Unslaked quicklime, semi-slaked “hydrated lime” and dry NHL powders might deteriorate in quality if they’re not stored in very dry and airtight conditions. Lastly, if you’re buying pre-mixed wet lime mortars containing NHL then you’re on the clock as it’ll start hydraulicly setting the minute it’s wet.

 

[iang]

Blue lias is a lot softer than Chert, so using an angle grinder down the centre of the joints first might help cut down the damage to the stone when you cut out with the chisel.
Limebase are a really good local supplier who are happy to give advice about the correct mortar to use. You can take a mortar sample in to them.

Thanks Stuart
I intend to get my lime from Limebase.

 

[iang]

I actually disagree. I think knocking it all off first gives the entire wall longer to dry out in the wind before sealing it back up with Lime. Then when you start repointing, you can start from the first section you removed cement from and work towards the most recently removed areas.

As for the lime storage on-site, it totally depends on the type of lime you’re wanting to use. A slaked putty that is covered in a layer of water will be absolutely fine, and might slightly improve in plasticity and workability (if you believe the old-timers) during the period. Unslaked quicklime, semi-slaked “hydrated lime” and dry NHL powders might deteriorate in quality if they’re not stored in very dry and airtight conditions. Lastly, if you’re buying pre-mixed wet lime mortars containing NHL then you’re on the clock as it’ll start hydraulicly setting the minute it’s wet.

Thanks for your reply.
I was going to use lime putty, so it seems it will keep OK on site for a while.

 

[Kearn]

I actually disagree. I think knocking it all off first gives the entire wall longer to dry out in the wind before sealing it back up with Lime. Then when you start repointing, you can start from the first section you removed cement from and work towards the most recently removed areas.

That’s another angle, and certainly how I’ve attacked stuff before when it’s not been excessive areas. God it gets tedious though…!

A lot depends on the elevation / weather / sheltering - you could also get the opposite with a ton of driving rain sucking into the mortar.

Think with all these things, when it was done historically, nobody gave it the thought now focused on it - the farm hand / labourer / local kids just got tasked with digging up and knocking up some muck and fixing stuff!

 

[stuart45]

Pointing is a tedious job, although not quite so bad when you're getting paid for it. I used to hate it when I was younger, but don't mind it so much nowadays. Depends on the job really, but I normally rake out the lot first and then repoint. This was the last barn I did a few years ago. Easy to rake out and the stone is a really hard Chert. Put a greenhouse on the end for him as well.View attachment 12312View attachment 12312

 

[aockenden]

Pointing is a tedious job, although not quite so bad when you're getting paid for it. I used to hate it when I was younger, but don't mind it so much nowadays. Depends on the job really, but I normally rake out the lot first and then repoint. This was the last barn I did a few years ago. Easy to rake out and the stone is a really hard Chert. Put a greenhouse on the end for him as well.View attachment 12312View attachment 12313View attachment 12314View attachment 12312

View attachment 12315

Beautiful work!

 

[Lacan07]

Thanks for your reply.
I was going to use lime putty, so it seems it will keep OK on site for a while.

A Lime putty ready mix bag will last forever as long as you don't expose it to extreme temperatures. NHL mortar usually comes in powdered form and should have a 'use by' date on it. I tend to ignore that though.

If you're planning on buying hydrated lime from a builders yard and making putty you should put a little aside and see if sets hard. That way you know that batch is good to go.

 

[iang]

Pointing is a tedious job, although not quite so bad when you're getting paid for it. I used to hate it when I was younger, but don't mind it so much nowadays. Depends on the job really, but I normally rake out the lot first and then repoint. This was the last barn I did a few years ago. Easy to rake out and the stone is a really hard Chert. Put a greenhouse on the end for him as well.View attachment 12312View attachment 12313View attachment 12314View attachment 12312

View attachment 12315

Thanks Stuart. Nice job. What tools did you use for raking out please?

 

[Toby Newell]

That’s another angle, and certainly how I’ve attacked stuff before when it’s not been excessive areas. God it gets tedious though…!

A lot depends on the elevation / weather / sheltering - you could also get the opposite with a ton of driving rain sucking into the mortar.

Think with all these things, when it was done historically, nobody gave it the thought now focused on it - the farm hand / labourer / local kids just got tasked with digging up and knocking up some muck and fixing stuff!

Well. Either small children, idiot farm hands OR 7 year apprentice trained tradespersons who were more skilled and experienced than most tradespeople today.

One of the two. Why do you think all these 400 year old houses made from lime and horse poo are still standing? Remember, a lot of work was done in kind and traded for other work or goods.

Now. Farmers. That's another matter altogether... I suspect farmers have always been farmers, Benny and the newborn to the rescue...

 

[stuart45]

Thanks Stuart. Nice job. What tools did you use for raking out please?

For raking out it depends on the type of brick/stone and mortar. For that barn it was easy because most of the joints were soft lime and worn back, and the stone is Chert which is really hard. For the few bits that were patch pointed in sand/cement I used an SDS.
However for yours, which is a much softer stone a lot more care is needed.
Here's a few of the tools I use for raking out.
Plugging chisels, some ground down a bit thinner, scutch hammer, brick hammer, serrated knife for tight joints.

 

[Kearn]

Why do you think all these 400 year old houses made from lime and horse poo are still standing?

Mostly because they were maintained and looked after correctly, evolving and adapting with time… equally, there are far more that aren’t here to show their neglect / poor initial construction methods and materials.

Remember, a lot of work was done in kind and traded for other work or goods.

That was precisely my point… it just got done. Can’t say I remember it though…

 

[iang]

For raking out it depends on the type of brick/stone and mortar. For that barn it was easy because most of the joints were soft lime and worn back, and the stone is Chert which is really hard. For the few bits that were patch pointed in sand/cement I used an SDS.
However for yours, which is a much softer stone a lot more care is needed.
Here's a few of the tools I use for raking out.
Plugging chisels, some ground down a bit thinner, scutch hammer, brick hammer, serrated knife for tight joints.View attachment 12389

Thanks Stuart. This is very helpful. Some of the stonework is quite soft so I'll use hand tools for most of the raking thanks to your advise and if I get stuck I'll use the SDS with great care and on a low setting to protect the stone.

 

[stuart45]

You can also try an angle grinder carefully along the centre of the joints to make it easier with the hand tools. It's usually a case of seeing what works best on the job. Problem with a hard mortar on a soft stone is that bits of stone often come away with the mortar.
All you do is damage limitation, and make it look good with the new pointing. Picking a good colour for the mortar can help improve the looks of the wall.

 

[iang]

You can also try an angle grinder carefully along the centre of the joints to make it easier with the hand tools. It's usually a case of seeing what works best on the job. Problem with a hard mortar on a soft stone is that bits of stone often come away with the mortar.
All you do is damage limitation, and make it look good with the new pointing. Picking a good colour for the mortar can help improve the looks of the wall.

Thanks again Stuart.
The angle grinder advise is very helpful. I'll be off to Screwfix to get one.
I've noticed that some of the newer additions to the barn have been built with cement but I'll need to complete the whole house and these areas will need to be repointed for cosmetic purposes even though there is no lime mortar under the cement pointing. I guess the angle grinder and sds drill will come in handy here.

 

[Stevers]

I've been working round my garden walls knocking out hard cement mortar and replacing with NHL mortar. I have a Makita SDS drill, and until you push hard it has an astonishing ability to gently 'tickle' the hard mortar out. The stone in my walls is variable, but includes softer Doulting stone. The SDS drill is absolutely my tool of choice for this work supplemented by plugging chisel and my Faithfull mortar pick. I do have angle grinders, but if I were to attack the wall with those, things would get very messy very quickly!

 

[Kearn]

Thanks Stuart. This is very helpful. Some of the stonework is quite soft so I'll use hand tools for most of the raking thanks to your advise and if I get stuck I'll use the SDS with great care and on a low setting to protect the stone.

As feeble as they seemed, and it was a cheap punt, a set similar to these have actually proven really useful. Obviously only once stuff is loose enough to remove (they’d struggle to do any damage themselves!), but you can get in behind to pull awkward shapes out from behind, rather than with other tools you end up pushing bits in further trying to get some purchase on them!

https://amzn.eu/d/brVkQne