Pointing

[Antwerpman]

hi,

I need to take out some old mortar and repoint between the bricks (the mortar is very sandy and crumbles easily). Some questions:-

What is the best way to get the old mortar out? Can I use a 4" angle grinder and if yes what disk should I use?

How deep do I need to go?

What is the best way to get the new mortar in there?

How do I know if the existing mortar is with/without lime and what is the effect if I use the wrong one?

Thanks

A

 

[oilman]

How old is the house?

What type of bricks are they?

If it's an old house treat it gently and carefully remove the mortar by hand using a chisel and avoid damaging the bricks (If it's a newish 1950's or later, you need info from someone else).

If you use lime, the mortar will be porus and pass moisture to the atmosphere and can be used on all joints as it will "wear" more than the bricks. If cement is used with bricks that are softer than the mortar, the bricks wear away leaving a lattice of mortar and cavities where the bricks once were.

Do the joints really need doing? If they do that's ok, but only repoint if NEEDED.

If you look round you can find loads of repointing that may be filling up "gaps" but it uses inappropriate mixes and spoils the building, where it's done sympathetically it looks brilliant.

 

[Antwerpman]

the house is about 100 years old, and is in Belgium (not sure if that makes any difference)

I dont know what kind of bricks are available so I dont know how to tell you what these ones are. They are smooth, red bricks but that is about all I can say.

The mortar at present is very soft and crumbling in places. So soft I can brush it away with my fingers and it is like sand almost. The bits that I need to do first are inside (in the loft) and will be painted so the appearance is not important but I would like to make sure I am not doing anything detrimental to the house. However later there are some areas on the outside (the chimney stacks mainly) that will need doing.

As there is a lot of surface to do I thought an angle grinder could be quicker. How much do I actually take out? The first inch or so?

 

[masona]

As there is a lot of surface to do I thought an angle grinder could be quicker. How much do I actually take out? The first inch or so?

Not too much otherwise more mortar to fill in. See this.
If the mortar is soft and crumbling as you say, might be easier to rake it out by hand tool.

 

[oilman]

I suspect it is lime mortor, and I'd replace it using the same and try and get the sand mix the same as the original.

I think you will have people in Belgium who are very good at looking after buildings to give you advice. In all of mainland Europe they did a brilliant job of repairing buildings damaged during the 1939-45 war. Not so in England, the small brained ones had most of them pulled down if they were damaged, and the same attitude exists here today.

 

[Antwerpman]

I managed to get some (ready mixed) lime mortar so I am hoping that there are not different types. On the internal walls which I will do first I am not too bothered about a colour match for the mortar as it will be painted anyway, so hopefully it will all be ok.

I can then check the colour match before I do the outside, but even the outside bits that need doing are on the chimney stacks some 10m high...so they dont need to stand up to close scrutiny

Thanks for the info guys, much appreciated

 

[TexMex]

I agree with Oilman that this is almost definately lime mortar.

Lime does not colour the mortar so much as cement. Sand, however, varies enormously in colour. If your new mortar doesn't match the colour of your existing joints, it is most likely that the sand has come from a different source.

If Belgian sand has anything like the variability that the British stuff has, it can be anything from light grey, to dark orange. Some areas even have dark brown or almost black stuff. This isn't just dependant on area, but supplies can change over time. The sand you buy at your local builders merchant today may come from hundreds of miles away. Whereas in the past (when your home was built) it may have come from hundreds of miles away in the opposite direction.

I'd hazard a guess that you would want 1 part Lime to 3 parts sharp sand, but do check locally. Unfortunately you are unlikely to get any specification as to what colour the sand should be. The only way you will find the right stuff, is to visit your local suppliers and look at the colour of thier sand, and judge if it is right for your job.

 

[oilman]

I hope the readymixed lime mortar doesn't have cement as one of the ingredients. If it doesn't, I envious that you can get the right stuff off the shelf. Almost everybody over here is hooked on cement and put it in everything. (Even pastry ). We now have firms who specialise in repointing. They have pneumatic injection guns and put in the most in appropriate mix they can think of, ruining buildings everywhere.

You can check the make-up of the mortar by scraping out a sample, and putting it in a 1.5 to 2cm dia bottle, add some water and shake it up, then let it settle (takes hours). You will see the layers of different grades of particles, and you could do the same test with potential supplies.

What about collecting all the mortar you rake out? There will be nearly enough to fill the gaps.

The lime mortar should be made up as dry as possible to pack into the joints, and some reading of how Belgian crafstmen used to do it will help you.

The information I had was a 2:1 mix by gauged volume was about right for lime, but Texmex may well have a point with 3:1. (The mortar you have could be just a mud mix too.