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Mortar for Re-pointing 1901 House Wall |
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| message from Phil Young on 18 May 2004 |
Apologies for asking this, but googling the group is giving me a massive
information overload. There must be thousands of posts about repointing
old wall, many of which contradict each other.
The situation is that I need to repoint a section of of wall of my 1901
end of terrace house (in Leamington Spa if that helps).
Looking at the wall, the bricks seem modern-ish - by which I mean that the
surface looks hard, almost shiny and the edges are well defined (except
the ones that have spalled below the DPC !).
Areas of mortar seem to have been replaced already in what looks like
concrete mortar - mid grey, very fine sand, very hard, can't press a
palette knife in at all. Under this is a much darker, much softer mortar
which I'm assuming is water damaged since you can more or less sweep it
out with fingers.
Finally, at little higher up there looks like the original mortar
(untouched). Dark grey, almost black, with large sharp-edged 'sand'
particles up to about 2 mm across, you can just about scratch it with a
palette knife.
So what is safest mix to use to repoint ?
From the zillion post I've read, it looks as if the consensus is a 6:1:1
mix (soft sand: Portland cement: Hydrated lime). This would be softer
than pure cement mortar and more convenient to make up that the Second
favourite, lime mortar (3 or 4:1 soft sand:lime putty).
Definitely to be avoided unless your certain the bricks are modern is the
cement:sand mix sold as pre-mixed mortar in the sheds.
I'd like to avoid the lime mortar option (for reasons of time), so will
the 6:1:1 mix be okay ? Does anybody have anything to add ?
Thanks,
Phil Young
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| steve replied to Phil Young on 18 May 2004 |
a cement dye to get desired colour? if just pointing a small area or
to match in with the neighbours etc
Also an easy way to rake out crumbly lime mortar is to use a wire
brush, hell of a lot easier than a pluging chisel.
If taking out the cement mortar over the lime try and crack it first
with a bolster as pluging chisel can sometimes bring away the suface
of the brickwork along with the cement
Pointing a smallish hawk (6" square) is usefull easier than using a
brick trowel I find
Steve
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| Phil Young replied to steve on 19 May 2004 |
Thanks for that. I wasn't too worried about a colour match so much as a
suitably weak/flexible mortar mix. So I'm going to try the 6:1:1 mix as
suggested by Michael. This will be a lot easier to make up than lime
mortar, since I can buy everything off the shelf (palette ?) at a shed.
Cheers,
Phil Young
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| Michael Mcneil replied to Phil Young on 18 May 2004 |
"Phil Young" <phil.y@ntlworld.com> wrote in message
news:pan.2004.05.18.14.46.22.800089@ntlworld.com
No problem.
The mortar in brick (and blockwork) should be softer than the brick.
Perhaps the replacement pointing has caused the lower bricks to spall.
They sound like engineering bricks though so perhaps not. Good quality
housing in the early 1900's would have had engineering facework with
very narrow beds and joints of mortar -usually sand and lime. Commons
and soft block would use 8 to 1 portland cement and sand (with small
particles.)
You can scratch the old pointing out a quarter to three eighths inch
with a peck hammer or use a grinder if the bricks are close together. An
hammer and chisel will take forever. See if you can get help with the
job. Either that or do a small section at a time. If the lower courses
are in a very bad way it might be worth thinking about rendering part of
the way up.
So was the house in a posh area in it's day? It doesn't matter much
-just nosey. You will be OK with 6:1:1. Use a small mix as it is a long,
tedious job until you get the knack of it. Don't use feb (plasticiser.)
Fill the joints flush and let them dry. As soon as possible an hour -or
not much more after, either brush the surface clean and level with a
soft handbrush, or use a "bucket handle" trowel.
You can get quite a nice effect on stonework pointing using a real
bucket handle to cut a parallel set of lines in it with a nice curved
bead inbetween. If the pointing is wide enough you might want to try
that. There is a knack to that too though. And more trime taken.
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| Phil Young replied to Michael Mcneil on 18 May 2004 |
Thanks, that was quick.......
Just popped out for a look, it's only a couple of bricks that have
saplled. Mixture of old and new pointing. The damaged bricks are all
under the original slate DPC and a more recent injected one though.
Probably not - the mortar joins all look about the normal 10mm. They're
'brick' coloured bricks btw, not the blue sort which is what I think of as
engineering bricks.
It's in a posh area now ! Just North of the town centre, so not as posh
as the Georgian bits. It did a step jump down the posh-o-meter recently
when a modern estate was built over some allotments a few hundred yards
away - my road is now on the shortest route to- and from- the fleshpots of
L/spa. As you can tell by the hordes of thugs passing by on Friday and
Saturday night.
<snip useful info>
I did a short brickwork course earlier in the year, so I'm quite happy
with the techniques. I just wanted to clarify what would be a suitably
weak mix to use to avoid doing any actual or further damage.
Thanks,
Phil Young
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