Advice needed on repointing.

[vannie]

I know this has probably been discussed to death on this forum but I need some urgent advice.
I have an edwardian house in need of repointing, has had some done in the past looks like a layer of cement placed over the sand and lime.
I have found some builders who are happy to point in whatever I request but would not profess to be experts in lime and sand mortar.
My question is do they need to rake out all the old mortar and what is the best ratio of sand to lime ? Also any other words of wisdom. I am terrified of it being done wrong and costing an arm and a leg. Also have only just managed to persuade my husband that we should not use cement.

Thankyou yur help.

Vanessa Southampton

 

[MdB]

I'll leave others to comment about removing the cement (my answer would be it is better to remove it unless the removal will damage the bricks).

Replace with 1 part hydrated lime to 3 parts sand. Absolutely no cement. Shouldn't be any more difficult for the builder to use compared to cement mortar but it must be allowed to dry slowly and wall should be dampened before applying. Tell builder he can also put any spare mixed up lime mortar into a sealed tub and it will be fine for use the next day (or the next month, year etc) as it won't set until dried out. Also don't be surprised that the lime doesn't have the strength of cement when dried. Its strength will improve but it will take years to reach full strength.

Show builder / husband these pics:
http://www.mikewye.co.uk/CementPointingLongwell.htm
Same applies to old bricks as they are not a strong as modern ones.

 

[tom.harrigan]

I'm interested in the use of hydrated lime for pointing. It's cheap and readily available, but there seems to be a lot of advice that it doesn't possess the magical properties of much more expensive putty.

T

 

[Nemesis]

We've had many posts on the subject.

There is opinion that it isn't as good and there is opinion that it is fine.

Take your pick.

 

[Mark]

there seems to be a lot of advice that it doesn't possess the magical properties of much more expensive putty.

Is that advice from the purveyors of much more expensive putty ?

bagged works for me. For pointing, render and plaster.

Of course you could always throw the bagged stuff in a plastic bin with water and do your own magic conversion to putty.

 

[Nemesis]

There are people who still have reservations whose opinions I respect, I have to say.

If you are using it, make sure it's fresh, and hasn't already carbonated in the bag.

And I think making putty first is a useful way ahaed.

 

[MdB]

If you are using it, make sure it's fresh, and hasn't already carbonated in the bag.

and has been stored in the dry.

For the record, I take bagged, convert to putty then leave for a couple of weeks where possible before mixing. But then I'm new to lime and I'm only really following what I've read here.

 

[Gervase]

The old mortar will need to be raked out to a depth equal to the width of the mortar course, making sure the back of the raking is squared and not rounded.
On no account should anyone be allowed near the walls with an angle-grinder fitted with a disc - although in the right hands a TCT or diamond mortar rake can be useful.
As for what sort of lime to use, my own preference is for putty - it's quicker and easier and less messy than using bagged lime, and with the quantities I get through (two or three tonnes a month at the moment) I can't be fagged to make my own putty!
The sand needs to be coarse - sometimes what a builders' merchant calls 'sharp sand' isn't gritty enough and you have to mix some concreting sand with it. If you're lucky, though, you'll be able to find an aggregate supplier or quarry who is used to dealing with conservation projects and will know exactly what you want and sell it to you for a fraction of what the builders' merchants charge.

 

[NT]

I know this has probably been discussed to death on this forum but I need some urgent advice.
I have an edwardian house in need of repointing, has had some done in the past looks like a layer of cement placed over the sand and lime.
I have found some builders who are happy to point in whatever I request but would not profess to be experts in lime and sand mortar.
My question is do they need to rake out all the old mortar and what is the best ratio of sand to lime ? Also any other words of wisdom. I am terrified of it being done wrong and costing an arm and a leg. Also have only just managed to persuade my husband that we should not use cement.

Thankyou yur help.

Vanessa Southampton

3:1 sand:lime by volume. Same ratio whether you use putty or dry lime, since dry lime doesnt change in volume significantly when made into putty. Cheap bagged dry lime works fine, no reason to buy ready made putty at profiteering prices.

The right lime is ordinary hydrated lime (not hydraulic)

No cement, that only causes premature failures.

Lime putty handles well, so builder should be quite happy working with it.

If you use dry lime it must be fully mixed, badly mixed bits would swell after application.

Lime is much slower to gain strength than cement, and this isnt a problem for pointing work.

Avoid pointing at times of frost, frost during set can break the lime up.

Normally remove only old pointing that will come away, whacking hard bits off only damages brickwork.

An angle grinder is probably the best tool for dealing with cement pointing, trouble is much care is needed with it. Put one in the hands of someone paid per job and it becomes a real menace.

Its very simple really.


NT

 

[Nemesis]

No, I'd be very wary of an angle grinder. Very wary.

There are pros and cons re using hydrate, it is cheaper but some people think it not so good. Others think it's fine. I appreciate that people like Gervase use vast amounts and won't have time to experiment with hydrate.

If you do I would certainly make it up into a putty and leave it.

 

[charlie-ia]

how do you tell if the bag lime is old and carbonated?

 

[NT]

Gone off cement clumps, gone off lime does, it looks exactly the same. Make a little putty & see if it sets solid in a couple of days. If its had it it'll dry out but not set, or only weakly set.


NT

 

[charlie-ia]

thanks, thats excellent!
weve just had our first go at it. the bag lime was very dusty and powdery. went everywhere! i want to make sure im doing it right, but its been great fun so far.
we made putty by using as little water as possible and mixing it with gloved hands untill it was like heavy pastry, and then making sure there were no airbubbles packed it tight into a bucket. then we gently poured the water on to cover it and let it sour.
we didnt add any extra water and let it drain abit before we mixed it into damp sand, again with gloved hands.

how much water should we be using? does it matter much?
we were just experimenting this week, inside a cupboard where the smoke comes through from the chimney where no one will see if we make a mess!
first time we did it we used the mix fresh, with no resting time, and the second putty we left for two days before mixing in the sand. it didnt seem much different, if any thing the second mix was a little wetter. they both seemed to stick ok and have started to set nicely.

if it was going to crack badly, would this become aparent quicky?
the mortar wasnt quite set when we left and we wont be back for a few weeks so its wait and see!

we have also left some putty maturing for next time we're there. its ok in a tin bucket isnt it?

the stuff we made came out much greyer than the origonal. we were going to mix the soil from the french drain in. its quite sandy deeper down, but not realy subsoil as the ground is banked up so steeply. else where we have thin topsoil over rock. how much can we use insted of the sand? does it matter about the organic material?

we wanted to also make some mud mortar and render as it has been used in several of the walls, but i understand we need to use subsoil because of the higher clay content. we have found soil the same colour as the mortar, that when packed down and left to dry, looks the same, but has no strenght at all and crumbled to dust. the mud on the walls doesnt seem to have much if any lime at all, and no hair or straw, so i dont undersand what sticks it together. any ideas?

 

[Mark]

I can only talk for myself but I make putty using lots of water - all the excess should do is sit on top.

I stir very well to avoid getting clumps of dry lime then leave it. I dont do the carefull pastry making that you have - in fact I think that that is not a good thing, potentially you are tight packing lime which isnt wet enough. I've tried both making lime only and also making plaster/mortar like this and it works for me.

Careful with the lime its nasty stuff - if you are getting it everywhere then get proper goggles - lime will cause serious eye problems,

I keep a hose of water and som evinegar to hand for cleaning up.

As to your earth stuff I suspect that you dont have enough clay if it crumbles to nothing - how deep are you digging?.

You can of course add lime to earth you might try that.

 

[MdB]

I turn hydrate into putty outside whilst wearing a mask. It really isn't something you want to breath. I also just pour in lots of water, mix carefully and then leave. The excess water I pour off before mixing into mortar.

 

[NT]

I do make some bad typos....

Gone off cement clumps, gone off lime doesn't, it looks exactly the same.

fixed


NT

 

[charlie-ia]

oh well, nevermind. we'll try drying a bit out and see what happens next time.

we mixed it with gloves because it was so dusty. using a spade or a stick threw it all in the air, and even in the barn its windy.

any recomendations for a good dust mask? the ones we bought were cheap, and worse than useless as you got so steamed up. a tshirt, tied cowboy style was better, but very uncomfortable

 

[Lime]

Downwind?

 

[charlie-ia]

mostly, but easy to get caught out by an un expected swirl.
need a good dust mask- theres no getting away from it.

 

[MdB]

It sounds like you are doing large quantities where as I've only done 10 litre tub sizes at a time but in the stuff I've mixed so far, the best technique I've found is as follows:

1) Quarter fill tub with water.

2) Fill tub to almost the top with hydrate using a scoop to transfer it from the bag. Don't try pouring it as it blows everywhere.

3) Add more water. Wait a bit and then add more water. You want a layer of water on the top so as to trap the dry hydrate.

4) Probe the mixture with a stick right down to the bottom so as to let the air out and the water in. Add more water if needed to keep a layer of water on the top. Don't worry about giving it a good mix at this stage.

5) Seal tub. Leave for a day.

6) Open up tub and give a good stir. It is at this stage you want to ensure that all the hydrate is mixed up.

7) Reseal and leave for a couple of weeks if you can. Pour off excess water before use (I use a sponge to get the last bit off).

The above process keeps the amount of hydrate in the air to a minimum as most of the time it is under water. I still wear a mask though. First mask was a cheap £2 one. Current mask is better, £10, but my glasses still steam up.