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Pointing with lime mortar ~ Part 2 = Mortar

Category: Starter for 10 December 31st, 2010 by mbc

Lime Pointing Tips

As I near the end of my repointing opus magnum I feel a little more qualified to advise on pointing with lime mortar than on most of the subjects I blather on about on this blog.

So here’s my take on all things lime mortar related – others may have differing guidelines – this is very much my take. This post is this second in the series.

Firstly, I covered the tools of the (pointing) trade now I’ll move onto lime mortar and how to make it.

From Pointing ~ tools

What went before?
When repointing an old building you may want to match the new mortar to the original mortar – a similar mortar mix, with a similar colour and texture. Many lime suppliers will analyse a piece of your original mortar and suggest the best way to achieve a match. Alternatively, you might want to do your own piece of psuedo-science and like me carry out your own lime analysis with a piece of the original mortar and an acid to dissolve the lime.

From your analysis you’ll start to form a picture of the exact mortar mix you’ll be using. You need to stick with the same mix for the whole of the job to ensure consistency of finish so make sure you’ve enough raw materials before you start.

Putty or powder?
One of the first questions you need to answer is what type of lime you’re going to use. There are two main choices – lime putty or powdered hydraulic lime.

Fat lime putty is produced by slaking quicklime with excessive amounts of water, thus forming a lime putty with a high water content. This form of lime does not set unless it comes into contact with air and so is ideal where some degree of flexibility is required – below the surface the lime does not fully set and so if the mortar cracks the newly exposed lime will set and re-establish a sound joint.

Natural hydraulic lime (NHL) dry powder products are similar in appearance and usage to dry powder cement products. Differing strengths of hydraulic lime products are available:

  • Feebly hydraulic lime (known as NHL 1 & 2), is slow setting (taking up to 20 days to set in wet conditions) and is suitable for internal use or external use where the masonry being pointed is very soft.
  • Moderately hydraulic lime (NHL 3.5), faster setting and used for pointing most types of stonework.
  • Eminently hydraulic lime (NHL 5), faster setting again and used for very exposed areas of pointing or floors.

As a rule of thumb you should never use a lime that sets harder than any masonry it’s in contact with.

Personally, I work with and recommend lime putty for pointing masonry walls which is where my experience lies.

Mortar Mixing
Powdered lime mortar can be treated pretty similarly to cement and a mixed by hand or in a cement mixer.

For mixing lime putty there are three main methods, in ascending order of ease and cost:

  1. By hand
  2. Using a drill with mixer attachment.
  3. By mortar mill (a £2000+ option)

I tend to mix small amounts of mortar as I use it – the equivalent of about four shovels-full of mortar lasts me about half a day. I use a drill with a mixer attachment. For most amateurs working on their own that is more than sufficient. Each mix takes 5 or 10 minutes and usually comes as welcome relief from starring at a wall. Originally I mixed by hand, which is a lot more time consuming, but good exercise and I certainly wouldn’t dissuade anyone from starting off in that way.

One advantage of using a putty based mortar is that any left unused can be stored, covered over and kept dry and then knocked up (that is worked briskly with a trowel) the next day or week ready to be used – only the top most layer will go off in contact with the air. Add a little splash of water if it dries out a bit.

Be careful when adding water to lime mortar at any stage – a little goes a long way.

You can also buy premixed mortar in which case no mixing is required. I’ve only come across a premixed mortar when being used by a neighbour – the mortar failed to go off and needed to be replaced so I’d certainly approach premix with caution.

When using a mortar gun you’ll need a smoother and sloppier mix than normal. No stones, pebbles or lumps of mortar or you’ll clog up the gun.

The mix I use, which gives a light coloured finish similar to the original mortar is:

  • 1 part lime putty
  • 2 parts builders sand
  • 1/2 (half) part kiln dried sand (for colour and to dry down the mix a little)
  • 1/2 part sharp sand
  • – this gives me some texture and a some particles than the builders sand alone, when using the mortar gun this can be left out to ensure a smooth mix

You’ll need to derive your own mix that suits your circumstances – then stick with it for the duration of your project.

In Part 3 I go on to discuss pointing technique

Previously… In Part 1 we looked at tools for pointing

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Pointing with lime mortar ~ Part 1 = Tools

Category: Starter for 10 December 23rd, 2010 by mbc

Lime Pointing Tips

As I near the end of my repointing opus magnum I feel a little more qualified to advise on pointing with lime mortar
than on most of the subjects I blather on about on this blog.

So here’s my take on all things lime mortar related – others may have differing guidelines – this is very much my take. This post is this first part of a series of 3 or 4 (I’ll see how I get on).

Firstly, I’ll cover the tools of the (pointing) trade.

From Pointing ~ tools

You need some pretty specialist tools for pointing. Nothing too exotic or hard to find, but I think it’s important to get the correct tools – tools that have the right size, weight and balance for the job. As a generally

For damping down the wall before pointing, you’ll need a good bristled brush and a bucket of water. I favour the ‘flick’ technique – water – bucket – dip brush and flick! Some people advocate the use of a garden water spray but that seems a little too fiddly to me.

From Pointing ~ picks

You’ll need a good hand pick or preferably two to allow for spreading them around your work area and keeping at least one close to hand. Use the pick for hacking out the old mortar to give a repointable joint. The pick will soon blunt and so a tool for resharpening is also recommended.

There are various machinery based options involving drill attachments and angle grinders that can be used for cleaning out old pointing joints, but I avoid them for fear of damaging the stonework.

From Pointing ~ hawk

To hold the mortar whilst pointing you need a hawk. Small pointing hawks rather than larger plasterers hawks are quite hard to come by, try your lime supplier first as they tend to stock them. A small hawk, by that I mean one that can accommodate a good trowel full of mortar and not much more is pretty essential when it comes to slow, delicate repointing work. Too large a hawk with too much mortar on it becomes surprising heavy surprisingly quickly.

From Pointing ~ trowels

I use two different size trowels, a normal sized pointing trowel for initially applying mortar to the joints and a smaller ‘trowel and square tool’ for finishing off – smoothing down the fresh mortar, cleaning off excess and filling small gaps. If you have straight mortar joints or need to work mortar into narrow recesses then a finger trowel may be of use, although mine is rarely used. I must admit to probably over-using the small trowel and encourage you not to do the same. I’m sure I could have worked much more quickly if I’d used a proper sized trowel whenever I could have. I’m trying to remedy that now by working with the larger trowel whenever possible, but I soon lapse back to my old ways if I’m not careful.

From Pointing ~ I’ve pointed
100 sqm+ with this sucker…

From Pointing ~ hammer

You’ll also need a masonary or brick hammer for hammering pinning stones into the original mortar bed to achieve a firm bedding before pointing (there’ll be more on what I mean by this in the technique section).

You’ll also need a wire brush or two (I always favour doubling up on tools that you’re not using all the time – with two around it’s more likely that at least one will be at hand). A hard bristled brush is also handy for cleaning off old lose mortar and misplaced or untidy dried new mortar. Do be careful when using a wire brush and try to keep it away from your nicely pointed joints as it will easily damage them.

From Pointing ~ gun!

I bought a mortar gun way back when I first started pointing. At the time I couldn’t get on with it at all. I’d try using it and usually give up in disgust at the amount of time I was wasting filling it, clogging it up, emptying it and repeating the whole cycle whilst achieving very little in the way of pointing. However, after much trial and error I came to a happy compromise with it and learnt when to try using it and when not to bother. The key is getting the mortar to the correct consistency (much sloppier than you’d mix for normal pointing) and like a good gravy ensure there are no lumps (of stone or lime) in it. Too firm a mix will clog the gun and you’ll end up pressing water out of the mortar rather than mortar out of the gun. Any lumps of stone or lime putty will block the nozzle of the gun and nothing will come out. As you’ll be using a sloppy and smooth mortar mix it’s only really suitable for filling deep or inaccessible holes in the mortar and in relatively dry conditions that will allow the mortar to lose a lot of moisture relatively quickly – I tend to not damp the wall down prior to using this mortar. In practice I only use the gun when I have deep and / or inaccessible joints to repoint. The gun does the bulk working, pumping quantities of mortar into the joints first, I then finish the top layer of pointing in the normal way by hand.

In Part 2 I go on to discuss lime mortar

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Lime Pointing ~ time trial

Category: Barn Conversion Journal November 2nd, 2010 by mbc

I’m trying to get the pointing finished this year, but it drags on and I could do with a change of scene. So although I’ve not yet finished the northern gable end I decided to finish the more straight-forward and visible back wall. I’d completed all along the bottom of the back wall – up as high as I was able to reach on a step ladder and so to finish the top I’ll need to use an extending ladder.

(As a slight aside, pointing from a ladder isn’t as awkward as it sounds – you can rest the mortar hawk and any tools you’re not using on the rungs of the ladder ahead of you and so can point one handed – which makes a change.)

But, how long would it take me?

To answer that question (and make a probably misguided attempt to make pointing exciting) I decided to undertake a lime pointing time trialhow much could I get finished in one hour? (You’ve got to give me credit for a least trying to make things exciting…)

Here are my results:


From Pointing

One hour later:

From Pointing

Now I realise that my results don’t exactly standout from these pictures (no I didn’t just move a ladder during the hour – if you look closely you can see the grey / brown pointing in the joints between the stonework on the second picture). I’ll take another picture next weekend after the mortar has dried to the off-white that the dry mortar lower on the wall is [See below – picture added November 2010]. I managed to point from the right hand corner to the left side of the ladder, with a couple of patches needing some more work and pointing started on some patches to the left of the ladder. To save some time I used a mortar gun to fill some of the deeper / wider joints and placed a few pinning stones in wide joints – which eats up some time.

My conclusion was that pointing at this rate I would need 8 to 10 hours to finish the back wall. That would be a long day’s work, or more likely a day and the following morning. I can then finish the top of the northern gable end in my own time…

We’ll see…

From Barn Conversion 2010

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Lime pointing ~ before pictures

Category: Barn Conversion Journal October 21st, 2010 by mbc

As much time as I’ve spent on pointing and all the ancillary activities such as moaning, evangelising and generally bumping-my-gums about pointing, I’ve just realised, I’ve not posted a great deal of evidence related to my actually doing any pointing.

To address this, I thought a range of before photographs, showing the walls of the barn in various states before being repointed was in order, to be followed by some evidential after photographs.

From Barn Conversion 2007

This picture from 2007 gives a view of the barn from the southerly end up and across the front toward the kitchen. No repointing, no lime washing, no new window openings, no new window frames or doors and no paths. The unadulterated version of the barn as we bought it.

The southern gable end had been repointed sometime in the previous few years.

From Pointing

Unfortunately, despite originally thinking that the pointing was good and sound having been recently repointed with what we thought was a lime based mortar, the repointing had actually been done with a cement based mortar that had cracked over time and so let in a lot of water. That end of the building catches the worst of the weather as it blows in along the valley and so is exposed to plenty of rain year round. So much water had worked it way in and dribbled down inside the wall that we had stalactites in our walls.

Repointing that wall would have been very difficult as the concrete mortar was very hard and virtually impossible to hack out by hand and the use of any machine was bound to lead to damage to the stonework. But something had to be done as the mortar was as leaky as a sponge. The solution we arrived at was to limewash it – a solution I’m pleased with for its practicality, attractiveness (well I find it attractive) and for the fact that it cut down the amount of repointing I needed to do.

From Pointing

I’ve left the other small patches of concrete mortar sprinkled around the other walls of the barn as they are – they’re sound and too hard to bother removing for purely cosmetic reasons.

The mortar in the long front wall that stretches away from the closest corner in the photo up toward the barn doors was the most rotten of all. In places it had rotted out or dissolved completely with lime loving plants growing out from the crevices.

From Barn Conversion 2007

This picture, again from 2007 shows the kitchen end of the barn, not long after the chickens had been evicted from their former home (they where relocated elsewhere on the farm, but apparently used to still come back to visit). You can see how rotten the mortar is in the lower left hand corner of the barn. The north facing gable end, in shade here, is the last I started work on. The original mortar on this wall was softer than on the other walls, I think partially due to the lack of sunshine ‘curing’ the mortar over the years. It gets very little sunlight, just some weak rays at the end of the day. I also get the feeling that as the least visible wall of the barn the original pointing hadn’t been done with as much care and attention to materials and technique as the other walls.

From Pointing
From Pointing

These pictures are more recent and show the walls at the rear of the barn having been prepared for pointing by hacking out old mortar. As you can see there were some very deep holes to fill.

From Pointing

Finally, a picture from 2007 of my first fledgling and somewhat messy attempts at pointing. Unfortunately I chose the most often seen portion of the barn walls that is passed by whenever entering or leaving the barn.

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Insulation ~ Foamed Glass

Category: insulation July 7th, 2010 by mbc

A strong yet light insulator, foamed glass is suitable for load bearing applications especially those demanding water and vapour resistance.


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Foamed glass insulation is made from (usually) recycled glass that is mixed with carbon and then heated to very high temperatures. Upon heating the carbon oxidises and forms bubbles in the resultant stone-like material. It is usually supplied as a gravel, but is also available in (very expensive) batts.


Typically in the range 0.037 – 0.048 W/m.K. (Watts per meter Kelvin ~ a lower value is a better result)

With strength comes cost …for gravel at a depth of 100mm, cost is around £15 per square metre or around £150 for a cubic metre bag.

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