"RobH" wrote in message
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On 31/05/2021 21:27, Rod Speed wrote:


"RobH" wrote in message
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On 31/05/2021 11:01, Rod Speed wrote:


"RobH" wrote in message
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On 30/05/2021 18:57, Rod Speed wrote:


"RobH" wrote in message
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On 30/05/2021 18:40, NY wrote:
"NY" wrote in message
o.uk...
On 30/05/2021 17:48, NY wrote:
Our house has a patio of stone slabs (slightly irregular size,
shape and thickness - not rectangular concrete slabs). They seem
to have been laid on bare earth, as far as I can see from looking
into the gaps, without levering up a slab to look.

Some of the mortar "grouting" between the slabs has cracked and
disintegrated, so I'm trying to re-mortar the broken bits. I've
removed the broken bits and brush away as much of the powder
residue that remains. I'm using ready-mixed mortar from B&Q, with
water added to form a stiff paste which is thick enough to adhere
to a palette knife so I can direct it into the gap (typically
5-20 mm) and then tamp it down with my fingers (wearing rubber
gloves in case the cement causes skin irritation).

I forgot to say: the mortar is brand new and the bag was only
opened a few days ago and has been kept in a dry garage.

It's made with grey Portland cement, not white lime.

Another thing I forgot to say. Where I've dug up the loose mortar
from when the patio was first laid (about 10 years, according to
neighbours), it's been a thin crust, in some places only about 5 mm
thick, with a large void below it down to the level of the base on
which the slabs have been laid. Is this normal? I'd have thought
the whole depth of the crack between slabs would have been filled
with mortar.


When I laid my patio , about 20 years ago, I put all the pavers /
slabs on a bed of sharp sand / cement mixed at about 7 or 8:1. I
have had to re point the gaps about 3/4 times since and I use a 3:1
mix of builders sand and cement with just enough water to make it
damp and no more. .

That works of for me.

Not very well tho given that you have had to redo the mortar 3/4
times.

That was over a 20 year period tho'.

Still nothing like what it should be. You dont have to repoint
brickwork at anything even remotely like a 7 year interval.

I'm not a builder so I have been learning as I go along so to speak.
Also I put it down to frost / extremely cold weather that has caused
the mortar to break up or go crumbly on the surface

You dont get that with brickwork either.

No I know that you don't get that with brickwork, but as I'm not a
builder what should I have done, ie method, mix or anything else, so it
doesn't crack, crumble or break up with cold weather.

Do a better job of point the slabs, correct mix, correct
water level, correct time of year when doing it.

Ok, so what is the correct way of pointing the slabs, if not with a trowel
What is the correct mix if not 3:1
What is the correct water level if not just enough to dampen the mix

Thats your problem. Thats not what is done with bricklaying.

And finally what is the correct time of year to do the job.

When the cement isnt washed away.