pointing a very narrow joint? (pic)

[still_adrianth]

Thanks everyone: I lurk and occasionally post; I love this forum.

Last year I started repointing our garden wall with 3:1 mix sharp sand : putty. Fine for the brickwork, but the joint between the bricks and the rounded top was too narrow to really get it in. I tried, and it looked fine at first, but the frost has broken it out. Look here:

How can that narrow joint between the rounded topping and the top course of bricks be sealed to stop water going into the wall (and freezing...)? Is making a lime mortar from soft sand an option (and what would the ratio be then)?

And, just out of curiosity, how was that rounded top formed? Is it limecrete or concrete? Original, or did all the neighbours get their walls re-topped later? All the neighbours' gardens (ca. 1918) have similar walls. There's an even finer vertical crack in the rounded top in the center of that photo. Not a big deal, but since I'm working there, what to do?

Thanks, anyone, for anything!

A.

 

[Moo]

Would it be possible to remove that top layer and re-lay it with a decent thickness mortar joint?

 

[JoceAndChris]

To me the top section looks like stone but I welcome correction. (make it severe :wink: )

Nice wall, still_adrianth!

 

[Andrew Bodenham]

You could try using a finer sand, and working the mix in with a brush, your fingers (gloved) or a very small trowel. But if you can't realistically point it then I'd just leave it alone. It's been ok for hundred years, it'll probably be ok for the next 100. Yes, water can get in, but it can also get back out again, so it's not really a problem. Certainly wouldn't consider taking it apart and rebuilding - if it ain't bust don't fix it. Ultimately it's only a garden wall.

 

[Gervase]

Essentially you're going to be tuckpointing the stones. For fine joints, use a 1:1 silver sand and putty mix, or for very fine joints, pure putty. Squash a pencil-sized sausage to the desired thickness between two sheets of greaseproof paper on your hawk and slide in a slice with a pointing iron - you may need to make your own by grinding down a piece of steel (or sacrificing a quarter-inch finger trowel like this) to the desired width.
Although, as Andrew says, it is only a garden wall, so you may just wish to brush a slurry into the cracks.

 

[OddJob]

I use a very thin,about 3mm jointer made from an old table knife on a bench grinder,the blade is about 5" long so pretty easy to get into deep cracks,1:1 silver or silica sand and lime putty,you could also add one part brick or stone dust.
To rake out thin joints in i.e. gauged brickwork or ashlar use a tungsten carbide tipped grout remover,for deeper joints rake out with tungsten carbide tipped tile saw blade or hacksaw blade,you can get them all from B&Q for a couple of quid each and the tile saw blade is particularly effective.

I happened to have one at home but the jointer is at work.
The capping looks like 5mm up sharp sand and cement,if it ain't broke don't fix it,you'll take brickwork away with it.
Open up the crack a little with a tile saw blade and use a similar mix to above but if it's cement you may as well use the same though I'd use hydraulic on the top.
You can make a slurry and inject it in with syringe,about 50p from any chemist,if it's deep fix a thin plastic tube to the syringe to get right down inside the crack,you can do the same on the joint but I normally just work off the hawk with the jointer.
I wouldn't brush it in personally,the above method will pack it in tight.

 

[OddJob]

Just to add to my previous reply the reason I don't think the rounded capping is stone is because of the lack of a bed joint which suggests a sand/cement/concrete capping that frost has lifted,I'm about to do a similar capping in hydraulic lime concrete on a ragstone wall.
You said the frost had blown the pointing you tried beneath the capping.
The crack is kind of inline with the perp below telling me it's part of the same movement in the wall.
If you open the crack slightly as I suggested you'll find out what the material is,or you could clean a patch.
Could be it is stone but look at the contours,they match the brickwork below.
Could be the mortar bed has lifted with it if it is stone and lichen etc blends it into one,but circa 1918 tells me it's a cement based capping.
In 1918 we didn't have a lot of good masons left to create a rounded stone capping,especially not on a garden wall,historically it was the end of the war and a great many of our craftsmen were lost.
If it's useful to you or anyone else I can post a pic tomorrow of the thin homemade jointer I use for such joints,it's pretty easy to make and extremely useful!

 

[essexbearhunter]

I used the PlasPlugs carbide hacksaw blades regularly (the yellow plastic mount shown in the picture was actually a ruler!) until they disappeared. They had shut down by February/March 2009 but later re-opened, initially in limited form. In their (temporary) absence I tried the Silverline ones and haven't really noticed any difference - apart from the price.

 

[still_adrianth]

That's all very interesting and useful: thanks everyone!

Yup, the top must be aggregate+cement: not stone, it was originally a continuous piece. Sorry my first photo didn't show that, so here's another:

I wan't sure if cement would have been used at the time (though it looks like it to me too), and was wondering how the rounded shape was formed - can you do it with just a stiff mix and a dextrous hand, Oddjob, or do you use some sort of former?

Thanks for the excellent suggestions to point the gap. You wouldn't think it would matter, but surprisingly it looks much nicer if the gap is filled. Even my wife said so, and she's free of pride-in-job bias on this one. We're on a hill, and there's a level change at this wall (hence the feeling that it ought to have some mortar in it) so it's prominent.

Is a "slurry" just the sand/putty mix with sufficient extra water added to make it brushable or injectable? I hadn't heard of these techniques: thanks. By the way, another source of syringes is printer ink cartridge refill kits. Good for injecting wallpaper paste into tricky places too.

Really pleased to know what to do now!
Adrian.

 

[OddJob]

You form the rounded top with a stiff mix and a wooden or plastic float,a bit like flaunching a chimney,best not to do it in one go though,I run a course of bricks through first(I'm doing this next week atop a ragstone wall)then part form the round with mortar,scratch it up then when it's dry finish with a second fairly thick coat.
You probably could use some kind of running mould but I've never tried,I've got Millars Plastering Plain and Decorative and I think there's something in there about it,not sure.

I know what you mean about pointing the gap,it'll look unfinished otherwise.
Yes the slurry is just a very wet mix,for deep grouting you can use casein,I know a stonemason who uses skimmed milk.
You'll have to use the stuff in the syringe pretty quick or it may clog,you could try a mastic gun but I'm not sure that would work,I've got the old Cox pointing/grout gun but it doesn't work well with lime,I've just bought the Pointmaster but not tried it yet.
For what you need to do you can just use a thin jointer and if needed a syringe.
Pic of homemade jointer.

The homemade jointer is second from right,all those jointers were in my tool bucket today and I've got more somewhere :shock:
I've lost my favourite,it'll turn up,I hope!
There's even a couple of genuine tuck pointers there about 200 years old and some handmade pennyrolls for good measure.
You don't need that many different sizes generally but I use different jointers for different jobs,three sizes are all most people need,the thin one is a very,very useful tool,I had another but gave it to my mate as he kept borrowing my good one and he gets pug all over the handles of tools even when cleaning them :roll:
A little tip,if you don't want to cut down a knife or perfectly good jointing iron go to the pound shop and get a pointing trowel for 99p then cut that down :wink:

 

[still_adrianth]

Thanks, OddJob, that really helps! And it's nice to understand how this might have been built.

It's wonderful how the web "democratises" trade knowledge (skill and experience remaining the tricky bits...), but this sort of thing very much relies on this forum.

One of the videos I saw on the web emphasised whacking the green mortar really hard with a stiff brush. I shouldn't have bothered because I pointed carefully so there were no gaps to compact. I got something like tennis elbow; no DIY for 6 months, had to brush teeth with left hand at the worst of it, more or less better after 8 months but weaker and fatter after not enough DIY and gardening! (I know I said this on another thread, but I really want to warn: tennis elbow is far more common from DIY than tennis. The psychological effects are worse than the physical if, like me, you get a sense of fulfillment from getting physical stuff done.).

A.