Repointing using lime mortar

[Marischal Ellis]

The advice from simoncmason is top rate and excellent to follow that; guide book. Gloves, goggles, really wetting the stone is most important as you dont want to suck water out of the mortar, nice to use, better than cement mix, colour agent is good when mixed and you get dark to lighter so you dont need to use it all. If facing some stone blocks then slight variations of colour looks better. Garden spray is excellent. Point twice if necessary and so point as a whole with final mix. Keep it covered and dont do it in warm weather. Can wash down wall face the next day, gently, to remove any smears as happens, with a light brush or wet sponge. Mix and mix if you are not using a mixer. Initially knowing how much to mix as a batch you will find out as you go. Lastly, Masons Mortars is good to have in Fife, Edinburgh and I think Glasgow with all necessary tools, hessian, etc and importantly the mortar mixes. A wide range of colour samples. In cities the curse to garden wall pointing is the road gritters with salt in the spray. You see the damage inflicted all over. Forgot.....rake out the old pointing to give a decent key and decent joint. You can do it in two layers to face off overall. You can use a picking hammer(ice pick) if it is hard but probably soft sometimes very soft.
Best wishes to all.

PS I have used them occasionally over the years.

 

[Sandyn]

Mix it for at least 30 minutes. Start with it looking on the dry side - you'll probably think it is too dry, leave it mixing, check after 20 minutes - it will look wetter than when you left it, you can always add a little (very little) bit more water to the mix at this point.

That's great information. How much did you mix at a time? can you leave the mix overnight then knock it up the next day?

 

[johnnyb]

I reckon as beginners always do the uk has overcomplicated the whole lime "thing". what's happened in france is what happened with portland cement years ago. the manufacturers came up with " solutions" that get sold into the building trade. nobody needs to slake there own lime or search for magic sand. they buy it in a bag and use it.
when lime was forgotten( in the 30s) it stayed at that level of technology. countries still using lime that has moved on. science experiments on building sites are difficult to repeat consistently.

 

[nickds1]

We have a large Victorian "Vine Wall" - South-facing with inbuilt chimneys to keep the frost off (very cunning, those Victorians!). Probably 15' high and 30' long...

Parts of it needed repointing as over the years it had had many 100s of iron nails & other iron bits hammered in that had since gone rusty and cracked the pointing - I filled over two builders buckets with the junk I removed from it.

There's a place near us (in Maidstone, Kent) that you can send a sample of the mortar from the wall to and they'll make up a matching mix.

Best advice they gave me: Draw a chalk line round the bit you want/intend to do and DON'T CROSS THE LINE!

There is an enormous temptation to "just do that other bit". It's a grim job, best left to some mindless oik with his headphones on...

 

[Sandyn]

It's a grim job, best left to some mindless oik with his headphones on...

That's me these days.

 

[simoncmason]

That's great information. How much did you mix at a time? can you leave the mix overnight then knock it up the next day?

I mix what I need - normally a bucket of lime and three buckets of sharp sand - which will keep me going for a few hours. If you mix a bigger load and then add a bit of water to it you can just about get away with leaving it over night if it is cool - but not freezing. But I don't think it is worth it. I just mix a load, use it, and then go and do something else - a few hours pointing at a time is enough for me. We have so much to do, house, barn and various other outbuildings inside and out that it is a case of chip away at it a bit at a time!

 

[WillM]

Anyone done it? I would like to repoint some parts of my house, using hydraulic lime, but it seems difficult to get the mix right and lots of scope for failure.

Specialists near us used building sand, but the colour is wrong for here. I asked a conservationist in Dorset what he was using: lime putty, building sand and stone dust - for the stone colour.

Lime putty is way more sticky than hydraulic so much easier to use.

I would mix hydraulic the night before and cover, minimum - the guy suggesting colour matching and a tub was on the money. It is basically how lime putty is made: slaking powder with water and leaving for a few years. For a flint wall I would sieve sharp sand to 2mm to get out any big chunks rather than use building sand. I’d mix 1:2.5, to get a stickier mix, cover and leave for a day, then knock it up again.

If you’re colour matching with old lime pointing I’d probably go for NHL5 - it’s greyer and also tougher.

 

[Adam W.]

Try not to over think it, it's really very basic.

 

[heimlaga]

The reason for slaking one's own lime is that the cheapest store bought slakelime is dry slaked. That is slaked with a shortage of water which leaves it powdery. Much easier to transport and sell as a powder in bags but much more didfficult to use.
The real stickiness is only developed when lime is wet slaked and left to react with the surplus water for a few weeks. Way easier to use especially for an amateur and no need for all those strange additives that industry wants to add to make the lime mortar sticky.
If one needs that extra stickiness in pure non-hydraulic lime one can either pay a premium for wet slaked lime or buy cheap dry slaked and wet slake it at home for a week or two.

 

[Adam W.]

You could just use bagged NHL from Kalkwerke Breckweg, which has a very high free lime content. It makes a beautiful mortar which is very different from other NHLs.

 

[Sandyn]

It is basically how lime putty is made: slaking powder with water and leaving for a few years.

not sure if I have a few years left!!