Exposed Cotswold Stone Wall Needs Sealing


C

Charlbury

Hi

Has anyone any experience or suggestions on what to use to seal an
exposed cotswold stone wall? I have read previous threads on using a
diluted PVA mixture and will probably go with this but I thought I
would see if anyone had actually done this on a cotswold stone wall.

Thanks
 
B

bigcat

Charlbury said:
Hi

Has anyone any experience or suggestions on what to use to seal an
exposed cotswold stone wall? I have read previous threads on using a
diluted PVA mixture and will probably go with this but I thought I
would see if anyone had actually done this on a cotswold stone wall.

Thanks
Why do you want to seal it? If its an old wall, sealing generally makes
them wetter, not drier, and is not at all recommended.

PVA certainly isnt suitable.


NT
 
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M

Mike

Charlbury said:
Hi

Has anyone any experience or suggestions on what to use to seal an
exposed cotswold stone wall?
It doesn't need sealing and doing so will cause severe problems in future.
If you are having problems it may be the pointing is failing though.
 
M

mark

Hi

Has anyone any experience or suggestions on what to use to seal an
exposed cotswold stone wall? I have read previous threads on using a
diluted PVA mixture and will probably go with this but I thought I
would see if anyone had actually done this on a cotswold stone wall.

Thanks
PVA is quickly destroyed by UV exposure.

Stupid idea!
 
P

Pete C

Hi

Has anyone any experience or suggestions on what to use to seal an
exposed cotswold stone wall? I have read previous threads on using a
diluted PVA mixture and will probably go with this but I thought I
would see if anyone had actually done this on a cotswold stone wall.

Thanks
Hi,

Why the need for sealing, is it suffering frost damage?

cheers,
Pete.
 
A

Anna Kettle

After it's destroyed the Laura Ashley presumably. Damp is not trivial and
the fact that we don't tolerate it in modern buildings is a mark of
progress
IMO. People before buildings I think.
I used to have a Victorian house and on the most exposed wall, no
emulsion paint or paper stayed good for more than a couple of years.
In hindsight I should have used limewash on that wall and kept the
Laura Ashley for the other three. There's no point fighting a losing
battle
None of these is impermeable to "moisture". We need to differentiate
between
water, as in rainfall, and water vapour which, being airborne, will travel
through virtually anything. The outside of a house needs to shed water
effectively but allow the passage of vapour which, fortunately, isn't that
difficult.
PVA and masonry paint are effectively a layer of plastic so water
vapour can't get through them.
Usually in the hope of preventing damp
And usually unsuccessfully
It gets in because the render cracks and water can pour through at a rate
of
knots. Why it cracks is IMO because it didn't adhere to the surface in the
first place so it moves due to its own weight. Cracks invariably
correspond
to larger areas of blown render, though which came first is open to
debate.
Agreed. And also cos the wall is built of brick and lime mortar which
will move slightly. Sand cement render is hard and brittle and doesn't
move, just cracks :(
Out of interest (and I really do mean that :), what mix do you use for
your
pargetting?
Often I use 3 parts chalk, 1 part lime putty plus goathair. Until
about 200 years ago chalk was used instead of sand around here. Why it
went out of fashion I don't know, but it makes a lovely malleable
mortar
Do you use pozzolans?
Not much these days cos much of my work is on timber framed buildings
which move around with the seasons and pozzolans make the mortar more
brittle (and resistant to weathering). When I was working in wet and
stony Wales I used pozzolans much more
Pips Cottage looks great and I can see why restoration is high on your
agenda but trying to stop a brick built terraced house leaking like a
seive is another matter.
Its the same matter actually cos both my timber frame and Victorian
terraces were built to breathe. Luckily I don't have a plastic
emulsion paint and Laura Ashley wallpaper lust. Pips Cottage has just
turned bright Suffolk pink but I won't post any new pictures until
I've painted black stripes on it so it looks just as wacky as it used
to do 100 years ago

Anna


~~ Anna Kettle, Suffolk, England
|""""| ~ Lime plaster repairs
/ ^^ \ // Freehand modelling in lime: overmantels, pargeting etc
|____| www.kettlenet.co.uk 01359 230642
 
M

Mike

Stuart Noble wrote:
Mike:



Mike. And the experts:
http://www.periodproperty.co.uk/cgi-bin/discussing/forum2.pl
and SPAB



he just did.

NT

Thanks for the support. Actually the key people who I'd trust making this
recommendation are the RICS special interest group on old properties as they
see all the damage done by incorrect approaches.

My approach to old and listed buildings which I restore is simple - no
sealing with PVA or other materials.


Can anybody tell me why I can't see any of Stuart's postings directly ?
 
B

bigcat

Stuart said:
So bricks and stones breathe, but cement doesn't?
1:1:6 does a little, but not enough for Victorian brick walls, 3:1
doesnt. Chalk does, granite doesnt. So not that simple.

After it's destroyed the Laura Ashley presumably.
you presume wrong. Millions of Vic properties are dissipating their
moisture this way, and dissipating it quickly enough that no damage
occurs to the wallpaper etc.

Damp is not trivial and
the fact that we don't tolerate it in modern buildings is a mark of
progress
IMO.
Victorian houses were dry enough 100 years ago, as they are today. The
idea that houses were horribly damp a century ago is a popular
misconception. Of course there would have been worse houses around, but
of those still up today, most didnt have a problem. Some do now as a
result of inappropriate modern work.

People before buildings I think.


None of these is impermeable to "moisture". We need to differentiate
between
water, as in rainfall, and water vapour which, being airborne, will travel
through virtually anything. The outside of a house needs to shed water
effectively but allow the passage of vapour which, fortunately, isn't that
difficult.
Cement render and gypsum allow vapour passage, but not enough.

I dont know why im writing this, you were given a good link and are
only being a wally.

cement

Usually in the hope of preventing damp.


It gets in because the render cracks and water can pour through at a rate
of
knots. Why it cracks is IMO because it didn't adhere to the surface in the
first place so it moves due to its own weight.
its one cause
Cracks invariably
correspond
to larger areas of blown render,
not always. cracks here that arent connected with blown areas.

though which came first is open to
debate.


Because a disproportionate amount gets through the cracks rather than the
impermeability of the cement.

Out of interest (and I really do mean that :), what mix do you use for
your
pargetting? Do you use pozzolans?
Pipps Cottage looks great and I can see why restoration is high on your
agenda but trying to stop a brick built terraced house leaking like a
seive
is another matter.
Controlling damp in Vic teraces is not achieved by stopping them
leaking, in fact that is moving in the wrong direction altogether in
most cases.


NT
 
C

Charlbury

It is an internal wall and it is in a kitchen. I want to remove any
(well almost any) chance of dust or debris from the wall onto work
surfaces.

Steve
 
C

Charlbury

Anna, any suggestions where I can get a small tub of Lime Putty from?

Thanks!
 
B

biff

There are quite a few places that supply lime putty now. Google for
"lime putty" and you may find one within striking distance. It usually
comes in 25litre tubs which is far more than you need but if you can
find a builder who understands how to care for old buildings he/she
will probably have some and let you have a small amount. Ring you
local Conservation Officer and ask if he knows anyone local that uses
it. As a last resort, you could use the hydrated lime that comes in
paper sacks at any builders' merchants. Put a cupful in a tub of
water, stir it up and leave for a day or two. Then use the resulting
lime putty in the way that Anna recommended.

Isn't it a shame that Stuart is so rude instead of being willing to
debate issues constructively. Some of us who use the Period Property
forum really do know rather a lot about their subjects and are more
than willing to share their experience. You won't find much enthusiasm
there for ever using Portland cement, gypsum plaster or any surface
covering that makes walls less 'breathable'.
 
B

bigcat

Charlbury said:
It is an internal wall and it is in a kitchen. I want to remove any
(well almost any) chance of dust or debris from the wall onto work
surfaces.

Steve
I think what you need is a porous stabiliser. Sealing is not
recommended. I'm told lime water is good for this.

NT
 
B

bigcat

b...@biffvernon.freeserve.co.uk said:
Isn't it a shame that Stuart is so rude instead of being willing to
debate issues constructively. Some of us who use the Period Property
forum really do know rather a lot about their subjects and are more
than willing to share their experience.
.... and are able to back up by citing the various expert bodies out
there, as well as explaining things in detail.

But you know what they say, a fool is one who calls the wise foolish,
and the foolish wise.

NT
 
B

biff

I would, and do, happily pay more than £6.50 for real lime putty made
the wet way and left to mature. Hydrated lime from a bag will do for
some purposes but there are differences. Womersleys have a good
reputation for selling good stuff. BTW I notice a bag of hydrated lime
at Jewsons is about £3 more expensive than at B&Q. Hmmm.
 
B

biff

Stuart, I'm not quite sure what you mean by "explain how lime can be
made water resistant without losing the properties which distinguish it
from cement".
Lime, when used in mortar for brickwork, allows water to pass through
the bedding planes. This water can then evaporate, keeping the wall
dry and protecting bricks from damage. This is particularly important
when the bricks are relatively weak and/or the wall does not have a
damp proof course. Both factors apply in many old buildings. Using
Ordinary Portland Cement either in the bonding mortar or for repointing
inhibits this moisture flow and makes it more likely that the wall
remains damp. External damage to bricks and internal damage to
decorative finishes may result. OPC mortars are stronger and harder
than lime mortars so tend to crack if there are any movements in the
wall. This is particularly important in old buildings that were not
built on stiff concrete foundations. Lime mortars accommodate movement
by forming micro-cracks which then self-heal by recrystallization of
the calcite. A small amount of water moving through the wall helps
this process. Substanial and costly foundations and damp-proof courses
are usually not needed for lime mortar bonded walls. When used as an
internal wall plaster, lime allows the movement of water without
sustaining any damage. Gypsum plaster disintegrates when wetted as the
hydrous and anhydrous forms of the calcium sulphate crystals have
different volumes. Lime mortars and plasters are not damaged by water.
Gypsum plasters are popular in the modern building trade where the
plasterer likes a quick set. Three coats and home for tea and start on
another job tomorrow. Working with lime takes time but the results are
compatible with the proper functioning of an old building in which
moisture management is critical. The use of any waterproof membranes
and sealants tend to interfere with this and should usually be avoided.
There is a considerable literature on the subject and I would suggest
you start with Jane Schofield's little book about lime, available
through SPAB, the Society for the Protection of Ancient Buildings.
Lime mortars and plasters are now the materials of choice for most most
Conservation Officers, English Heritage, the National Trust and others
concerned with the care of buildings from before the early 20th
century.
There are also sound arguements on sustainability, cost and aesthetic
grounds, for using traditional materials such as lime, brick, timber
and linseed oil in new builds rather than Portland cement, steel,
gypsum and petroleum-based paints and sealants. As we move into the
era of oil depletion it may not be an option.
 
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B

biff

Well, I realise that you can use pozzolans to make lime set, but it
then
takes on the undesirable properties of cement and loses its self
healing
capabilities.
Yes, pozzolans and Natural Hydraulic Lime is best restricted for
special situations - lighthouses, bridge piers, maybe chimneys.
"So in a 9" wall driving rain passes through the mortar and ends up
where?
Does it evaporate to the inside?
Yes, but even in Wet Wales there is more time when it is not raining so
more water moves in the other direction. Most of the damp in a house
comes from people breathing, cooking, washing and watering their
potplants. The problem is getting rid of all this water without it just
condensing on the wall and then spoing the decoration.
If cement stops water getting in, there isn't a probelm with it getting

out. The wall doesn't get damp in the first place.
Think of the house like a goretex jacket - a plastic mac keeps the rain
out but you get sweaty, a breathable fabric keeps the rain out and
keeps you dry inside when you perspire.
They do not affect the appearance
Personal taste is involved in aethetics but on a historic building you
would probably not get Listed Buildings Consent to repoint with OPC so
if you did use it you would be guilty of a criminal offence.
5-10 year periods
are a short time in the life of a building, or should be.
sand cement
mortars do not reliably adhere to old brickwork.
Often true, lime mortar is more reliable when correctly applied. On
the other hand, brickwork bonded with OPC mortar often sticks so firmly
to bricks that they cannot be cleaned it the building is ever
demolished. The bricks cannot then be reused easily. Old bricks with
lime mortar are easy to clean and given a new life in a new building or
a repair of ann old one.
But anything on the plaster will be damaged, which rules out wall
coverings
The damage is usually caused by water from inside condensing on the
inner surface of the wall. Water from outside is more likely to come
from damaged rainwater goods or soil accumulating against a wall at its
base rather than from rain wetting the wall's surface.
All very well but, in the real world, your average punter has to deal
with
your average builder.
How terribly true. We do have a great task in educating the building
industry.
There are plenty of areas where modern materials can help with
conservation.
The Victorians couldn't have preserved the Mary Rose.
Yes, and the use of resins and steels are invaluable in preserving
historic fabric where, for example, joist ends have rotted. I'm no
Luddite, but am interested in both caring for our heritage and building
sustainably for the future.
 

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