Brick re-pointing

FrankGrimes

The bricks on my 1949 house need to be repointed. I have just treated them with a special acid and washed them down to clean off the layer of paint that was put on them. While doing this a lot of pointing fell out so it'd be the best job to redo the lot.

We're putting on an extension to the side so the aim was to get bricks back to original colour to get a colour match of the original colour for the bricks for use in the extension.

The existing pointing was painted black but once the acid removed this its clear it was white underneath. I'm fairly sure its a lime mortar: this white substance is only there for the final ~20mm and its normal cement mortar behind it, so the lime mortar can be chiselled out separately.

The bricks are wirecut red rustic and the pointing is the old style Struck (or Weathered) finish. I believe I need to stay with a Weathered finish as the existing bricks are not frost resistant (though the new ones will be).

Should I really go for a lime mortar finish or would a normal cement mortar finish with a Weathered pointing finish be ok? Also, we don't like the white finish of the lime, would prefer something a bit more grey - can lime mortar be dyed?

I will be removing the existing mortar myself and if its in any way possible would like to do the re-pointing aswell, but if its definitely a job for the pros I'll engage one, but would like to do it myself if possible.

Viking House

We have a few bags of Hydraulic Lime left over from a job in Shankill.
We used lime plaster internally on an extension there.
Lime plaster is much better for bricks as it lets your wall breathe and it sucks moisture out of the wall.
Just mix it 2:1 with sand.
The lime is free if you want to try it.

rooferPete

Hi Frank,

I'm afraid this is one of those times "Doctors Differ and Patients Die"

Brick work of that era was usually built using mortar and struck pointed later using a strong sand / cement mix 2:1.

The reason being the bricks were very often porous so the water was encouraged to run off the surface by the strong mix.

When re-pointing it is best to rake out the joints and start re-pointing from the top down using plenty of water poured in between the joints, this has two results, the first being the most important is the sand / cement mix will not dry out too quick and crack instead the water gives it a chance to bond to the bricks, the second is the water running down the wall will clean off any dust and debris as you go.

You will need a good scaffold and plenty of patience to do this work, a job often left for a special type of brick layer / stone mason affectionately known in the long past as a "Wigger".

When you have completed the work apply at least two coats of a product called "Enviroseal B", this allows the bricks to breathe but leaves the surface waterproof.

.

FrankGrimes

thanks for the replies, not sure I get the doctors differ comment though Pete?

I have almost finished removing the existing pointing and found that it came out quite easily in most parts, and the mortar underneath is quite crumbly. I'm thinking of using a weak mix polybond PVA diluted in water and brushing this in between the brick joints to help get a better adhesion when the new pointing is applied. Would this have any negative effects as it might provide a waterproof layer between mortar and new pointing? I'd have to be careful not to get it on the bricks.

I'll be getting the brickies to do the new pointing. The brickies agreed that the existing pointing is lime, but they say the Trowel Ready Mortar which they will be using for the blockwork will be fine for the pointing as 'it contains a good bit of lime'. I checked the Roadstone product listing here and can't see any mention of lime. Any ideas if would this be a good mortar for the 1949 bricks?

If not, how much hassle would it be for the brickies to use a lime mortar (i.e. mix time, separate applications of mortar and pointing on new bricks)? Would hydraulic or non-hydraulic be best? And can is it easy to add a dye to make it finish as a light grey?

Many thanks.

rooferPete

Hi Frank,

Doctor's differ is just a nice way of referring to the fact that Viking is a professional (Doctor) some put me in a similar class

I would Forget the PVA all it will do is stop the sand / cement from bonding to the wet brick.

As for your brickies well if you read my earlier post you can imagine what I think of them, it's not their fault they weren't raised in restoration work like I was.

Lime is not needed for pointing it's for building bricks, that is why the bedding behind the original pointing is crumbling, it was meant to allow the building to move (slightly) and to breathe.

Ask your brickies where do they want to "Sour the mix" for the pointing or the building of the new brickwork for that matter.

I am very interested in what their reply will be.

Ready mix mortar (even without cement) does not contain lime it has a chemical substituite because lime can cause efferesence (SP ?) on the brickwork, also known as lime bloom.

The colour is not a problem, you can add cement dye to your barrel of water that you will be using in the mix, that way you get an even colour in the pointing.

.

Viking House

Hi Dr. Pete and Frank

This is what I think;
If you point with cement the mortar is harder than the bricks and keeps the wall damp, when you get frost the front part of the brick can crumble and breaks off.
The lime being softer prevents this from happening. The lime lets the wall breathe and dry out.
Hydraulic lime gets harder quicker so is better for your job.
I also appreciate that Pete has more experience than me on this.

Here is an article on lime,
http://www.constructireland.ie/articles/0212lime.php

FrankGrimes

Thanks again for the insightful responses.

So is it a case that if I use cement based mortar rather than lime the bricks will suffer or is it a case that they may be damaged?

The brickies seem decent enough and know what they're at (e.g. they mentioned the frenchman tool for Weather Struck pointing) but if its as you both say then it seems theyre systematically using incorrect mortar on all their jobs? Is that common? Do you recommend using lime mortar for the entire joing or just the last 20mm up to the outer edge?

They mentioned that doing it with lime mortar would involve mixing the lime with white cement he called 'snow' and sharp sand - does that sound right?

Whats the working time of a lime mortar mix using hydraulic lime (i.e. if I mixed it for them on Sunday how long would it last?)

The joints between the existing blocks are roughly 16mm and they explained this was due to the lack of plastic aditives in the old days so a large bed of mortar was needed to get work the brick into it. They suggested best way of replicating this in the new bricks will be waiting for the trowel ready mortar to dry out a bit so that it will take the weight and still stay 16mm deep.

Appreciate all the advice and am just trying to find out if this is a big enough issue to kick up a fuss about as if its not a red-flag issue I'll avoid taking them to task on it.

FrankGrimes

Considering as tomorrow is pretty much deadline day for me to make a call on this it would be great if you guys could outline what you think the best approach would be here so I can put it to the brickies. The more clued in I sound the less likely they'll be to try fob me off .

What mix would you recommend and should it be used for the entire joint in the new bricks or just the last 20mm?

We want the pointing to finish to a dark grey, as considering the pointing is 16mm the colour of it has a major impact and we feel bright colours look cheapish alongside these bricks for some reason. What would need to be added to the mix to get this colour?

Go raibh maith agaibh.

Viking House

Give me a call Frank 087 6558699

FrankGrimes

Many thanks for all the excellent info over the phone Viking House, much appreciated.

I talked the brickies into going with the lime mortar for the pointing, so I'll gladly take that hyrdaulic lime you have.

I'd be able to collect in Shankill tomorrow morning if that suits?

What is the correct name of the type of sand I should use?

Thanks again.

FrankGrimes

Many thanks again to RooferPete and Viking House for valuable info on this subject, and thanks for the lime Viking House, much appreciated.

I mixed up a little bit of lime and sand to do a test area to see how it turns out. I asked for sharp sand in Heiton Buckleys but they said all they had is 'building sand' which says 'Plastering Sand' on the front, pricey stuff too. Not knowing what 'sharp sand' is or the difference I took what they offered cos it'll end up in concrete along the way somewhere if not right for the lime mortar.

I basically got 1 small scoop of hydraulic lime, and 3 scoops of sand and dry mixed it just using a trowel in a bucket. I then added a small bit of water (surprised how little was needed) and again mixed with a trowel for a minute. When doing it properly I'll obviously be using a cement mixer. I then put this in as a small bit of pointing and sponged off where I got it on the bricks. The sand is quite gravelly and so is giving that kind of effect, but won't know what it really looks like until tomorrow I suppose.

Is there anything I should be doing to ensure its a better mortar and better finish? To be honest, in terms of substance it didn't appear much different to cement mortar, but maybe thats due to the coarse sand.

If necessary can I use normal cement dye to get the colour I'm looking for?
The restoration of the bricks and pointing has become a labour of love I suppose and I'm delighted with getting the bricks back to their original colour and am optimistic that the new bricks are a good colour match, so just want to get this last bit right.

Viking House

If you mix in cement or dye the lime or paint over the pointing you could affect the hydroscopic (the ability of your wall to sweat) properties of the mortar.
It will get greyer in the next few months.