On 31/05/2021 23:23, Rod Speed wrote:


"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 sandÂ* / 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 enoughÂ* 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.

Thanks for not answering the questions about mix and water level.

Bricklaying is a different matter as it is vertical, slab laying is
horizontal and therefore more chance of frost and ice adhering to the
mortar.

The cement is not washed away, as I did not say it was.
Never mind, if you don't know, some one else will tell me.