Pointing Old Brickwork

[Edward W. Thompson]

I need to repoint some old brickwork (circa 1920). What mortar mix should I use? I have 'Googled' and find the advice there both confusing at sometimes contradicatory. There seems to be 'ready' mix mortar available (just add water) but some advise against shed bought pointing mortar mixes.

A related question, has anyone any experience of pointing using a 'pointing gun'? From 'Google' they seem to be a very neat answer to the job but I guess their usefulness can only be gauged by someone without hours of experience and practice. I need it for a one off job, about 30feet or so, 5ft high wall and at about £20.00 it may be worthwhile provided they 'work'.

[Andrew Gabriel]

Depends on the bricks and the existing mortar used. The mortar needs to be weaker than the bricks (or it will damage them), and if the wall is built with lime mortar, it needs to be able to cope with movement of the wall. You haven't given enough info.

It is unlikely that's suitable for repointing a 1920's wall. It's likely to be too strong and rigid.

I would suggest you find out how to do it properly, and start with an area which doesn't show, not the front wall of your house.

[Stuart Noble]

IME they don't work at all with mortar.

[4square]

I once repointed outhouse, at back of my 1925 house, but it was not on view really. Raked out joints to about an inch, used weak mix, no lime. More difficult than it looks! If this wall is highly visible, I reckon best to seek out a local builder who does work on older houses. Most local councils coservation sections know of such, for work on listed buildings, maybe worth a call.

[Phil L]

If you've never done re-pointing before, I wouldn't contemplate using one of these applicators. And definately *NOT* ready mixed mortar - it's far too sharp and far too strong for pointing. You need red building sand, mixed at 4 or 5 to 1 with ordinary portland cement (use a measure so that the same ratios are used every day until it's finished - it can be anything - a plantpot or an old cup etc)

Start at the right hand side of the wall and work to your left, that is, so that you are dragging the pointing trowel from left to right when smoothing off the courses - this gives you something to work to - if you do it the other way, you are dragging it towards an empty joint.

Do a 3ft wide patch at a time and do all the down joints first, then the cross joints.

If the wall has been whizzed out with a grinder or it's in poor condition, you may need to wet it down before you start - use a watering can and pour water down the wall which will remove dust and also give the mortar a better bond, don't worry about wetting it too much - it dries out within minutes.

[Stuart Noble]

Good advice

Have you found a way to do the down joints easily? No problem tucking the horizontals in off a mortar board or whatever, but those verticals I find frustrating

[Phil L]

You should be able to slice off a suitable sized piece of mortar and hold it vertically on the trowel without it falling off, if you can't then the mixture is wrong. Soft sand. Little water. Plenty of fairy liquid - at least a teaspoonful for every Kg of mixture, it should end up like soft clay....the fairy gives it adhesion qualities

[Stuart Noble]

Cheers. I'll pay more attention to texture in future

[Anna Kettle]

If you were using lime mortar you wouldnt hve to mess about with fairy liquid ...

Anna

[Edward W. Thompson]

How do I tell whether the bricks are 'hard' oir 'soft'? It appears to me that the bricks are 'soft'. Incidentally the project is a garden wall, not the house. It is my 'inclination' to use lime mortar. I would think that would be suitable regardless of brick 'type' (am I wrong here?). After all lime mortar use to be used on stone built structures and you can't get bricks much harder than that.:).

That's exactly what I thought.

I have done pointing before, whether it was done 'properly or not is debatable :-)! My primary question, that no one yet seems to have answered, is what mortar mix should I use? I suppose 'Google' will give me that info if I opt to use a lime mortar. Is there any reason not to use lime mortar?

I don't really understand comments made with respect to 'pointing' guns. Having viewed videos from 'Google', they really do look to make the job much 'easier' but clearly the consistency of the mortar mix is all important so it extrudes from the 'gun' smoothly. In this respect I would have thought a 'plasticiser' would help but many seem to warn not to use plasticisers, why?

[Anna Kettle]

Dont do it until the risk of frost is past.

Rake out the joints well, damp down and pack with the lime mortar, trying to keep it off the face of the bricks. Protect with hessian sheeting or similar. Leave until there is some resistance to your pointing tool (24hrs or so), then go back and consolidate. Aim to get the pointing more or less level with the surface of the bricks dont do raised or struck pointing or such frippery. Protect and leave again. When the mortar is firm to touch then bang it with the bristles of a stiff brush. Protect a few days longer

Thats off the top of my head so I may have missed something out

I'd go for

3:1 soft sand:hydraulic lime (NHL3.5 or NHL 5 depending on risk of / concern about frost damage)

Anna

[David in Normandy]

I'd add some cement dye too if you need to match the colour of the existing mortar. Lime mortar is almost white otherwise.

[Anna Kettle]

Do the arrises tend to rub away (soft) or chip off (hard)

Anna

[Andrew Gabriel]

I wouldn't use fairy liquid anyway. It's packed with soluable salts to thicken it which you don't want left in the wall. Buy a bottle of proper plasticiser, or use cement with plasticiser included (which half the bagged cement sold has anyway, if you check the packet).

[Stuart Noble]

You say don't mess around with Fairy Liquid. Then you go on about having to protect the pointing with hessian for a few days. Now I call that "messing around". One of these days someone is going to explain the real world difference between hydraulic lime and a weak soft sand cement mortar. I suspect it's mostly cosmetic

[Anna Kettle]

I'm not the expert but I can point you in the direction of the definitive answer:

Hydraulic Lime Mortar published by Donhead Publishing

Cement is heated to a higher temperature than is hydraulic lime which must affect the chemistry somewhat but you are right that strong hydraulic lime and weak cement are on the same scale. I have seen a scale of hydraulicity which from memory was something like

0 - Putty lime 3.5 - Natural hydraulic lime NHL3.5 5 - Natural hydraulic lime NHL5 8 - Early cement (it was invented in 1820) 20 - Modern cement

But there are all compared using a standard amount of aggregate.

A weak mix of concrete ie lots of aggregate and little cement doesnt fit on that scale so I dont have a comment there. Maybe the book does

- its the report of a lot of research done for British Standards or EU standards or suchlike

Anna

Anna

[Steve Firth]

Yes, I have a huge amount of pointing to do on a wall built of rubble, stone, brick and tile fragments. It's near impossible to point in a reasonable period of time because of the complexity of the joints. I bought a gun last year and have been working away bit by bit doing about a square metre at a time.

The builder sneers at me and makes comments about "amateurs" but I'm working faster than he does and making a better job of it. You still need a pointing trowel, a frenchman for finishing the joint and I find a number of window and margin trowels useful because of the varying widths of joints.

helps a lot if you can get two guns and also if you can have someone to mix the mortar and fill the guns. Scaffolding or a platform also helps.

[mail]

Dear Edward Read "Mortars, Plasters and Renders in Conservation" by J Ashurst (obtainable from the SPAB) All will be revealed On a quick skim of the other posts I agree entirely with Anna I would never use a gun to apply as to get it filled and working requires an in appropriate mix in the first place Basics are to

1) find out if it is a lime or cement based mortar in the first place 2) make up a similar mortar 3) rake out well and point only arris to arris at the horizontal part (ie JUST the bed depth if there is any wear on the arris) Chris