Phil Addison wrote in message . ..
On 23 Jun 2004 04:48:41 -0700, (N. Thornton) wrote:

Phil Addison wrote in message . ..
My daughter's house has had a patch of damp appearing under the upstairs
windows since she bought the house 5 years ago from a builder (I did
warn her!!) who had done it up to re-sale. There was no sign of damp
then, it all being freshly decorated.


Hi

If the builder rendered the whole place that is something of a caution
sign. You dont generally render without good reason - although
unfortunately some fools do. Walls are often rendered when its too
much work to fix problems with them.

Eeek. I'll do some exploratory drilling to check the extent of this.

I cant think how drilling would tell you whats going on. If theyre not
cracked externally I'd leave well alone in most cases.


Must say the brickwork under the patch I exposed is pretty ropey.

The interior leaf of Victorian walls is normally rough. Yours looked
fairly OK, though I couldnt see it too well in the pic, so I might be
wrong. If the wall starts to collapse when exposed then its time to
worry. It does happen. If its nothing but a pile of loose rubble,
again attention needed. Yours looked serviceable, at least from this
distance.

I was
going to repoint it before plastering, ut maybe I should render it (with
no waterproofer additive) as well after all to bind it all together?
OTOH, it only has a few courses to self support just there.

Ideally both, but mostly people just render. Many Vic houses are a bit
borderline structurally, so maximising wall strength can matter on
some of them. Do use the right mix on Vic bricks, the wrong mix can
end up doing more damage.


Tarred surfaces stay waterproof far longer than
oil based paints and so on. You cant easily paint over tar though.

I wasn't reckoning on tarring it - don't think my daughter would
appreciate that.

It would be black. Some tar based paints can just be painted on like
any other paint.


Any waterproof paint would do for a while, but really you want

any idea how long. As I say, it is done now with silicone, but I
anticipate having to redo it unless I put an overcoat of something on,
such as one of those recommended in this thread.

only for vague ballparks, gloss tends to have fallen off in 2-3 yrs,
pliolite maybe 10 years+. But YMMV significantly.


something with good long life, as water penetration again would do a
lot of damage.

And ideally use internal plaster that lets any dampness dry, like lime
plaster. But only once the wall's properly dried.

What is lime plaster?

plaster made from lime Most plaster is gypsum based. Lime
plastering costs more, but may be easier to diy since you get more
time to work on it.


Any water penetration anywhere can be expected to freeze and slowly
disintegrate whatever its freezing in.

Right. So a dpc under the sill is not the answer, so the sill must be
waterproofed.

right

It sounds like you're on the right track if you've sealed the cill.
The chances of it being porous are quite remote and if it is, you
could probably cure this with a water repellant.

Not sure about 'sealed', but I hope so. I sprayed them twice with stuff
sold for treating penetration problems in walls. Can't recall the name
at the moment.

Sounds questionable to me.

Just have to wait and see if it dries out,

yup.

or the 'blutak dam' tells me anything.

doubtful, penetration is liable to be uneven.


I used Unibond silicone from B&Q, about £7 a tube.

try toolstation.com, something like 1.50 IIRC

Thanks. Noted for next time.

screwfix price about the same too.


Regards, NT

On 26 Jun 2004 16:42:37 -0700, (N. Thornton) wrote:

Phil Addison wrote in message . ..
On 23 Jun 2004 04:48:41 -0700, (N. Thornton) wrote:

Eeek. I'll do some exploratory drilling to check the extent of this.

I cant think how drilling would tell you whats going on. If theyre not
cracked externally I'd leave well alone in most cases.

I was thinking of a 1/4" drill just through the plaster to see if it hit
render or brick. To see if the whole wall/s is rendered or just the damp
bits.

I was
going to repoint it before plastering, ut maybe I should render it (with
no waterproofer additive) as well after all to bind it all together?
OTOH, it only has a few courses to self support just there.

Ideally both, but mostly people just render. Many Vic houses are a bit
borderline structurally, so maximising wall strength can matter on
some of them. Do use the right mix on Vic bricks, the wrong mix can
end up doing more damage.

By 'both' you mean repoint + render, or render + plaster? I suppose the
former. The right mix is...?

only for vague ballparks, gloss tends to have fallen off in 2-3 yrs,
pliolite maybe 10 years+. But YMMV significantly.

So it'll be pliolite for this job then (or the similar magnolia
mentioned earlier).

And ideally use internal plaster that lets any dampness dry, like lime
plaster. But only once the wall's properly dried.

What is lime plaster?

plaster made from lime Most plaster is gypsum based. Lime
plastering costs more, but may be easier to diy since you get more
time to work on it.

I like the sound of that. I take it you buy it by the bag ready mixed?

Just have to wait and see if it dries out,

yup.

or the 'blutak dam' tells me anything.

doubtful, penetration is liable to be uneven.

Oh well, I'll try it anyway. If the level doesn't go down it will be
encouraging. Will have to shield it from wind and sun though.

Phil
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On Sat, 26 Jun 2004 13:01:50 +0100, "stuart noble"
wrote:


Phil Addison wrote in message ...
Had a look at it after some rain and was pleased to see droplets rolling
around on the sill. I appreciate it may not last very long though (any
estimates?)

IME 6 months or so.

Another reason for pliolite or similar.

These products are usually siloxanes which, unlike silicone,
don't form a continuous film. They cure as microscopic pellets of
grease/rubber which can be dislodged by (although not soluble in) water.
Same stuff they use for dpc injection I think.

Are you sure? I'm no chemist but once talked to the chemi-lab of the
makers of Solignum when I was injecting it as a dpc. They told me that
the stuff is not intended (indeed does not) fill up the pores of the
bricks, but coats the internal surfaces of the pores with a very thin
layer which changes the surface tension so that water does not rise past
it. The upshot of this is that you can repeat the treatment if the first
was inadequate.

I'm no chemist either but www.sovchem.co.uk might give you some ideas.

That's both of us then.

Phil
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Phil Addison wrote in message . ..
On 23 Jun 2004 04:48:41 -0700, (N. Thornton) wrote:


Eeek. I'll do some exploratory drilling to check the extent of this.

I cant think how drilling would tell you whats going on. If theyre not
cracked externally I'd leave well alone in most cases.

I was thinking of a 1/4" drill just through the plaster to see if it hit
render or brick. To see if the whole wall/s is rendered or just the damp
bits.

That wont really tell you anything about the condition of the wall. It
is external rendering that is the caution sign, not internal. And
drilling wont tell you anything useful.


I was
going to repoint it before plastering, ut maybe I should render it (with
no waterproofer additive) as well after all to bind it all together?
OTOH, it only has a few courses to self support just there.

Ideally both, but mostly people just render. Many Vic houses are a bit
borderline structurally, so maximising wall strength can matter on
some of them. Do use the right mix on Vic bricks, the wrong mix can
end up doing more damage.

By 'both' you mean repoint + render, or render + plaster? I suppose the
former. The right mix is...?

repoint and render. For repointing Vic bricks I use 1:1:6, thats
cement:hydrated lime:sand by volume. However I'm not going to state
that would automatically be correct in your case, it probably is but
its upto you to confirm.


And ideally use internal plaster that lets any dampness dry, like lime
plaster. But only once the wall's properly dried.

What is lime plaster?

plaster made from lime Most plaster is gypsum based. Lime
plastering costs more, but may be easier to diy since you get more
time to work on it.

I like the sound of that. I take it you buy it by the bag ready mixed?

I think Anna said Jewsons do it - you can search. I've not used it
yet, so cant give you much info there. G'luck.


Regards, NT

On 27 Jun 2004 06:13:27 -0700, (N. Thornton) wrote:

Phil Addison wrote in message . ..
On 23 Jun 2004 04:48:41 -0700, (N. Thornton) wrote:

I was thinking of a 1/4" drill just through the plaster to see if it hit
render or brick. To see if the whole wall/s is rendered or just the damp
bits.

That wont really tell you anything about the condition of the wall. It
is external rendering that is the caution sign, not internal. And
drilling wont tell you anything useful.

OK, I thought you meant internal. I'm not touching the external
rendering.

By 'both' you mean repoint + render, or render + plaster? I suppose the
former. The right mix is...?

repoint and render. For repointing Vic bricks I use 1:1:6, thats
cement:hydrated lime:sand by volume. However I'm not going to state
that would automatically be correct in your case, it probably is but
its upto you to confirm.

Well, it's only a small area and not supporting anything much. No idea
how to confirm that other than asking on here. It goes without saying
that any advise given here is taken at ones own risk.

I like the sound of that. I take it you buy it by the bag ready mixed?

I think Anna said Jewsons do it - you can search. I've not used it
yet, so cant give you much info there. G'luck.

I'll take a look at Anna's posts. Thanks for all the advice.

Phil
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On Sun, 27 Jun 2004 19:14:43 GMT, Phil Addison
wrote:

On 27 Jun 2004 06:13:27 -0700, (N. Thornton) wrote:

Phil Addison wrote in message . ..
On 23 Jun 2004 04:48:41 -0700, (N. Thornton) wrote:

I was thinking of a 1/4" drill just through the plaster to see if it hit
render or brick. To see if the whole wall/s is rendered or just the damp
bits.

That wont really tell you anything about the condition of the wall. It
is external rendering that is the caution sign, not internal. And
drilling wont tell you anything useful.

OK, I thought you meant internal. I'm not touching the external
rendering.

By 'both' you mean repoint + render, or render + plaster? I suppose the
former. The right mix is...?

repoint and render. For repointing Vic bricks I use 1:1:6, thats
cement:hydrated lime:sand by volume. However I'm not going to state
that would automatically be correct in your case, it probably is but
its upto you to confirm.

Well, it's only a small area and not supporting anything much. No idea
how to confirm that other than asking on here. It goes without saying
that any advise given here is taken at ones own risk.

I like the sound of that. I take it you buy it by the bag ready mixed?

I think Anna said Jewsons do it - you can search. I've not used it
yet, so cant give you much info there. G'luck.

I'll take a look at Anna's posts. Thanks for all the advice.


After getting thoroughly confused about whether to point and render,
with what mix, or to just point then go straight for browning, or
bonding, onto the brickwork, I have opted to point and render, so have
bought a bag of lime, one of Ordinary Portland Cement, and a couple of
bags of sand. I propose to mix 1:1:6 by volume (OPC:Lime:Sand) with no
waterproof additive.

I'll use this to point and then go straight on to a render scratch coat,
and finish off next day (or maybe the one after) with a skim of Thistle
Finish if I can find some, otherwise multi-finish. The standard bags of
lime and cement are, I am pretty sure, far more than i need for this 4x2
patch, though it is quite deep in places, up to 1.5".

Does that sound OK? That's tomorrow's plan, so please shout quick if it
needs modifying!

Further sill treatment with w/p paint will come later.

I'll update the photos with the result if I'm not too ashamed of it - my
plastering is still in the learning phase!

Phil
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On Tue, 29 Jun 2004 22:16:45 GMT, Phil Addison
wrote:


Further sill treatment with w/p paint will come later.

Did it absorb any water in the end? Might be worth cleaning it with
silicone eater if you need to paint it.

cheers,
Pete.

Phil Addison wrote in message . ..

After getting thoroughly confused about whether to point and render,
with what mix, or to just point then go straight for browning, or
bonding, onto the brickwork, I have opted to point and render, so have
bought a bag of lime, one of Ordinary Portland Cement, and a couple of
bags of sand. I propose to mix 1:1:6 by volume (OPC:Lime:Sand) with no
waterproof additive.

I'll use this to point and then go straight on to a render scratch coat,
and finish off next day (or maybe the one after) with a skim of Thistle
Finish if I can find some, otherwise multi-finish. The standard bags of
lime and cement are, I am pretty sure, far more than i need for this 4x2
patch, though it is quite deep in places, up to 1.5".

Does that sound OK? That's tomorrow's plan, so please shout quick if it
needs modifying!

sounds like an excellent set of choices. The only thing I'm uncertain
about is what mix would be best for the internal rendering. I've asked
people here about it, on ukdiy, so will see what they say. Last time I
did something similar I put a thin layer of 1:1:6 on then filled the
rest in with 1:1:4. That way the bricks see soft mortar so they dont
get admaged later, and you still get a lot of the wall and surface
strength of a stronger mix. And I believe the lime content has limited
crack healing ability.

BTW the pointing can be done extremely quickly by putting on a glove
and just smearing handfuls of mortar along and into the joints. Since
its about to be rendered over it doesnt matter a monkeys what it looks
like.


Further sill treatment with w/p paint will come later.

I'll update the photos with the result if I'm not too ashamed of it - my
plastering is still in the learning phase!

Lol, I've got that to look forward to here too G'luck.


Regards, NT

On 30 Jun 2004 09:44:26 -0700, (N. Thornton) wrote:

Phil Addison wrote in message . ..

sounds like an excellent set of choices. The only thing I'm uncertain
about is what mix would be best for the internal rendering. I've asked
people here about it, on ukdiy, so will see what they say. Last time I
did something similar I put a thin layer of 1:1:6 on then filled the
rest in with 1:1:4. That way the bricks see soft mortar so they dont
get admaged later, and you still get a lot of the wall and surface
strength of a stronger mix. And I believe the lime content has limited
crack healing ability.

Oh well, it's done now with just one coat of 1:1:6. At least I aimed for
1:1:6 but the finished surface looks quite brown so I hope I haven't got
too much sand in it. It went on ok though, and stuck ok, so hopefully it
is ok.

I made a tool to level it consisting of a long straight batten that
reaches the sound wall on either side. To that I nailed a strip of ply
protruding 4mm, and length slightly less than the width of the cavity.
The idea being that this would scrape the render flat and leave 4mm
clear for a plaster skim. That worked out quite well.

I have scratched the surface and left it to go off overnight. How long
does it normally take to go off enough to plaster, or should I wait till
it is dry (Andrew said to skim after 24hrs but I think that was on a
bonding scratch coat) - I suppose it is about the same. Anyway I
finished about 8pm tonight so plan to start the skim Friday morning.

One worry I have is that I tested the brickwork to see how much it had
dried out, and according to my squawking detector, it hadn't dried out
much at all. However my window sill has droplets on it from light rain
so I reckon that is reasonably silicone proofed, and I am hoping the
squawk from the detector is due to residual salts in the bricks, along
with some moisture.

Phil
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On Wed, 30 Jun 2004 13:15:10 +0100, Pete C
wrote:

On Tue, 29 Jun 2004 22:16:45 GMT, Phil Addison
wrote:


Further sill treatment with w/p paint will come later.

Did it absorb any water in the end? Might be worth cleaning it with
silicone eater if you need to paint it.

I'm leaving that test till later and concentrating on finishing the
interior work. This is to be a nursery and baby is due in 10 weeks so my
daughter is understandably anxious to have it finished. FWIW there are
water droplets on the sill after rain so it seems to be proofed so far.

Phil
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Phil Addison wrote in message . ..
On 30 Jun 2004 09:44:26 -0700, (N. Thornton) wrote:

sounds like an excellent set of choices. The only thing I'm uncertain
about is what mix would be best for the internal rendering. I've asked
people here about it, on ukdiy, so will see what they say. Last time I
did something similar I put a thin layer of 1:1:6 on then filled the
rest in with 1:1:4. That way the bricks see soft mortar so they dont
get admaged later, and you still get a lot of the wall and surface
strength of a stronger mix. And I believe the lime content has limited
crack healing ability.

Oh well, it's done now with just one coat of 1:1:6. At least I aimed for
1:1:6 but the finished surface looks quite brown so I hope I haven't got
too much sand in it. It went on ok though, and stuck ok, so hopefully it
is ok.

should be fine in that respect.


One worry I have is that I tested the brickwork to see how much it had
dried out, and according to my squawking detector, it hadn't dried out
much at all.

Oh, I'd assumed you'd let it dry first. I'm unclear how its going to
dry out.


However my window sill has droplets on it from light rain
so I reckon that is reasonably silicone proofed, and I am hoping the
squawk from the detector is due to residual salts in the bricks, along
with some moisture.

Those compounds get rid of the surface tension, hence the droplet
formation, but that does not block the pores. It makes less water soak
through rather than none. The thing needs proper waterproofing.

At this point I have some reservations. Maybe someone else will chip
in here.


Regards, NT

In article ,
(N. Thornton) writes:

sounds like an excellent set of choices. The only thing I'm uncertain
about is what mix would be best for the internal rendering. I've asked
people here about it, on ukdiy, so will see what they say. Last time I
did something similar I put a thin layer of 1:1:6 on then filled the
rest in with 1:1:4. That way the bricks see soft mortar so they dont
get admaged later, and you still get a lot of the wall and surface

I use 1:1:6. The render isn't the facing surface indoors anyway
(I assume you will skim it afterwards).

strength of a stronger mix. And I believe the lime content has limited
crack healing ability.

Lime acts as a plasticiser and makes the mix easier to handle.
I doubt if you are going to get much in the way of tollerance
to movement unless you take the cement out. I also use a
waterproofer (actually combined waterproofer and plasticiser,
so I end up with a lovely creamy/smooth mix to handle).

BTW the pointing can be done extremely quickly by putting on a glove
and just smearing handfuls of mortar along and into the joints. Since
its about to be rendered over it doesnt matter a monkeys what it looks
like.

It's silly to point if you're about to render. The unpointed
surface will provide a much better key for the render, and if
you are applying the right pressure, the gaps will be filled
anyway. Do remember to PVA the brick.

--
Andrew Gabriel

Phil Addison wrote:
I [ ... ] have bought a bag of lime, one of Ordinary Portland
Cement, and a couple of bags of sand. I propose to mix 1:1:6
by volume (OPC:Lime:Sand) with no waterproof additive.

To late now, except for discussion, but why no waterproofer?


I'll use this to point and then go straight on to a render
scratch coat, and finish off next day (or maybe the one after)
with a skim of Thistle Finish if I can find some, otherwise
multi-finish. The standard bags of lime and cement are, I am
pretty sure, far more than i need for this 4x2 patch, though
it is quite deep in places, up to 1.5".

If damp penetrates your internal render, you will gey problems
with the plaster. Damp and gypsum plasters don't mix!


J.B.

(Andrew Gabriel) wrote in message ...
In article ,
(N. Thornton) writes:

sounds like an excellent set of choices. The only thing I'm uncertain
about is what mix would be best for the internal rendering. I've asked
people here about it, on ukdiy, so will see what they say. Last time I
did something similar I put a thin layer of 1:1:6 on then filled the
rest in with 1:1:4. That way the bricks see soft mortar so they dont
get admaged later, and you still get a lot of the wall and surface

I use 1:1:6. The render isn't the facing surface indoors anyway
(I assume you will skim it afterwards).

I've done some 1:1:6 rendering now, and I have to agree with you
there, its plenty strong enough.


strength of a stronger mix. And I believe the lime content has limited
crack healing ability.

Lime acts as a plasticiser and makes the mix easier to handle.
I doubt if you are going to get much in the way of tollerance
to movement unless you take the cement out. I also use a
waterproofer (actually combined waterproofer and plasticiser,
so I end up with a lovely creamy/smooth mix to handle).

In lime mortar, lime reacts with CO2 to grow a crystal across the
crack, and this self healing provides some movement tolerance. I'm not
sure if there may still be a bit of this action with a lime cement
mix, but the lime can still meet the CO2, as the plaster would crack
at the same time, so it seems quite likely, unless perhaps you know
about all this in greater depth.


It's silly to point if you're about to render. The unpointed
surface will provide a much better key for the render, and if
you are applying the right pressure, the gaps will be filled
anyway. Do remember to PVA the brick.

First it depends on the depth of the gaps and how much pressure is
applied when rendering. Second it literally takes about 2 minutes to
repoint quite a big area with a glove. Its just a way to ensure you
get max strength there. It doesnt always matter, often doesnt in fact,
but Victorian buildings are sometimes marginal and those ones need any
strength they can get. With those ones filling the mortar gaps fully
does matter, so I think its worth 2 minutes to avoid a risk.


Regards, NT

On 1 Jul 2004 05:44:05 -0700, (N. Thornton) wrote:

Phil Addison wrote in message . ..
On 30 Jun 2004 09:44:26 -0700, (N. Thornton) wrote:

Oh well, it's done now with just one coat of 1:1:6. At least I aimed for
1:1:6 but the finished surface looks quite brown so I hope I haven't got
too much sand in it. It went on ok though, and stuck ok, so hopefully it
is ok.

should be fine in that respect.

Yes, it dried out hard enough (and didn't fall off overnight - hooray!),
but the surface had lots of loose sand from the scratches, which I
brushed off before skimming. I had a 'test sample' of mix left over and
that seems hard enough to do the job though you can dig into it with a
screwdriver blade.

Oh, I'd assumed you'd let it dry first. I'm unclear how its going to
dry out.

Can't wait for it to dry out any more - pregnant daughter needs the room
decorated as a nursery. My hope is that the remaining dampness in the
wall will dry through the non-waterproofed render and the skim. If it
all goes pear-shaped, at least this render is very weak and will hack
off easier that the rock hard stuff that was on before.

However my window sill has droplets on it from light rain
so I reckon that is reasonably silicone proofed, and I am hoping the
squawk from the detector is due to residual salts in the bricks, along
with some moisture.

Those compounds get rid of the surface tension, hence the droplet
formation, but that does not block the pores. It makes less water soak
through rather than none. The thing needs proper waterproofing.

I hear what you say and intend to apply some Pliolite type paint as belt
and braces when I can find my round tuits. However, my understanding is
that Solignum works by coating the inside of each pore such that the
capillary attraction required for porosity is negated. As I said
earlier, their lab told me it is not intended to block the pores, and I
suspect that would be impossible to achieve in practice. The evidence of
my eyes in seeing perfectly spherical raindrops sitting on the treated
sill tells me that those drops are not penetrating it. I'm not saying
this is how it works, it's just what they told me, but I am inclined to
believe it.

At this point I have some reservations.

Err.. ?

Phil
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On Fri, 2 Jul 2004 09:51:58 -0700 (PDT), Jerry Built
] wrote:

Phil Addison wrote:
I [ ... ] have bought a bag of lime, one of Ordinary Portland
Cement, and a couple of bags of sand. I propose to mix 1:1:6
by volume (OPC:Lime:Sand) with no waterproof additive.

To late now, except for discussion,

Very true, skimmed it today.

but why no waterproofer?

To let the damp bricks dry out via it (hopefully!).

If damp penetrates your internal render, you will get problems
with the plaster. Damp and gypsum plasters don't mix!

I am working on the assumption that I have cured the on-going water
penetration and there is a limited quantity of damp left in the 11" wall
that needs to breath its way out. I may be wrong, in which case I could
be doing it all again next summer :-(

Phil
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On 2 Jul 2004 11:07:36 -0700, (N. Thornton) wrote:

(Andrew Gabriel) wrote in message ...

It's silly to point if you're about to render. The unpointed
surface will provide a much better key for the render, and if
you are applying the right pressure, the gaps will be filled
anyway. Do remember to PVA the brick.

First it depends on the depth of the gaps and how much pressure is
applied when rendering. Second it literally takes about 2 minutes to
repoint quite a big area with a glove. Its just a way to ensure you
get max strength there. It doesnt always matter, often doesnt in fact,
but Victorian buildings are sometimes marginal and those ones need any
strength they can get. With those ones filling the mortar gaps fully
does matter, so I think its worth 2 minutes to avoid a risk.

It was not so much pointing, more just filling the crevices before
spreading on the render coat. A couple of the bricks were actually loose
so I wanted to stabilise them. Didn't know about the glove trick, but as
it was all to be covered I just offered up a blade of muck and shoved it
in the gaps with a small trowel. It didn't take any significant time.

Phil
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On 2 Jul 2004 12:45:33 GMT, (Andrew Gabriel)
wrote:

I use 1:1:6. The render isn't the facing surface indoors anyway
(I assume you will skim it afterwards).

Yes, done now with Thistle Finish.

Lime acts as a plasticiser and makes the mix easier to handle.

The bag I got said it wouldn't 'work' unless you used cement as well (as
sand presumably), and said it is better still to mix it up as a
lime-putty and let it marinade for 24 hrs. Didn't do that, but without
digging out the actual words again, I got the impression it had some
strengthening effect as well as plasticising - in fact it didn't mention
plasticising, though I know from previous use that what you say is
right. And yes, it was pretty easy to handle.

Do remember to PVA the brick.

Oh dear ,I didn't, is it doomed? :-(

Phil
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Phil Addison wrote in message . ..
On 2 Jul 2004 12:45:33 GMT, (Andrew Gabriel)
wrote:

Do remember to PVA the brick.

Oh dear ,I didn't, is it doomed? :-(

not at all. Brushing the wall with water is another way to do it:
yours is already wet.

Regards, NT

Phil Addison wrote in message . ..
On Fri, 2 Jul 2004 09:51:58 -0700 (PDT), Jerry Built
] wrote:

If damp penetrates your internal render, you will get problems
with the plaster. Damp and gypsum plasters don't mix!

I am working on the assumption that I have cured the on-going water
penetration and there is a limited quantity of damp left in the 11" wall
that needs to breath its way out. I may be wrong, in which case I could
be doing it all again next summer :-(

Lets just hope your idea's right.

Regards, NT

In article ,
(N. Thornton) writes:
(Andrew Gabriel) wrote in message ...

strength of a stronger mix. And I believe the lime content has limited
crack healing ability.

Lime acts as a plasticiser and makes the mix easier to handle.
I doubt if you are going to get much in the way of tollerance
to movement unless you take the cement out. I also use a
waterproofer (actually combined waterproofer and plasticiser,
so I end up with a lovely creamy/smooth mix to handle).

In lime mortar, lime reacts with CO2 to grow a crystal across the
crack, and this self healing provides some movement tolerance. I'm not
sure if there may still be a bit of this action with a lime cement
mix, but the lime can still meet the CO2, as the plaster would crack
at the same time, so it seems quite likely, unless perhaps you know
about all this in greater depth.

No, and I've found it pretty impossible to get definative info.

However, a lime mortar is flexible, so in the event of movement,
you get many smaller-than-hairline cracks which are self-healing
as you say -- lime is exposed and reacts with CO2 to make more
chalk, which is what the lime becomes when it sets. However,
1:1:6 is not flexible to the same degree, and you will get fewer
larger visible hairline cracks, which the lime isn't going to be
able to do much about. I think the significant things about the
1:1:6 mix is it's not so strong that in the face of movement it
makes the bricks crack, and it doesn't take the days/weeks a
lime render takes to go off -- you can skim it after 24 hours.

--
Andrew Gabriel

(Andrew Gabriel) wrote in message ...
In article ,
(N. Thornton) writes:

strength of a stronger mix. And I believe the lime content has limited
crack healing ability.

Lime acts as a plasticiser and makes the mix easier to handle.
I doubt if you are going to get much in the way of tollerance
to movement unless you take the cement out. I also use a
waterproofer (actually combined waterproofer and plasticiser,
so I end up with a lovely creamy/smooth mix to handle).

In lime mortar, lime reacts with CO2 to grow a crystal across the
crack, and this self healing provides some movement tolerance. I'm not
sure if there may still be a bit of this action with a lime cement
mix, but the lime can still meet the CO2, as the plaster would crack
at the same time, so it seems quite likely, unless perhaps you know
about all this in greater depth.

No, and I've found it pretty impossible to get definative info.

However, a lime mortar is flexible, so in the event of movement,
you get many smaller-than-hairline cracks which are self-healing
as you say -- lime is exposed and reacts with CO2 to make more
chalk, which is what the lime becomes when it sets. However,
1:1:6 is not flexible to the same degree, and you will get fewer
larger visible hairline cracks, which the lime isn't going to be
able to do much about. I think the significant things about the
1:1:6 mix is it's not so strong that in the face of movement it
makes the bricks crack, and it doesn't take the days/weeks a
lime render takes to go off -- you can skim it after 24 hours.


Lime mortars seems to be a complex and confusing subject! I guess not
many folk using it, so info is patchy.

Regards, NT