Exposed Cotswold Stone Wall Needs Sealing

Discussion in 'Misc DIY' started by Charlbury, May 9, 2005.

  1. Charlbury

    Charlbury Guest


    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.

    Charlbury, May 9, 2005
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  2. Charlbury

    bigcat Guest

    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.

    bigcat, May 9, 2005
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  3. Charlbury

    Mike Guest

    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.
    Mike, May 9, 2005
  4. Charlbury

    bigcat Guest

    bigcat, May 10, 2005
  5. Charlbury

    bigcat Guest

    bigcat, May 10, 2005
  6. Charlbury

    mark Guest

    PVA is quickly destroyed by UV exposure.

    Stupid idea!
    mark, May 10, 2005
  7. Charlbury

    Pete C Guest


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

    Pete C, May 10, 2005
  8. Charlbury

    Anna Kettle Guest

    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
    PVA and masonry paint are effectively a layer of plastic so water
    vapour can't get through them.
    And usually unsuccessfully
    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 :(
    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
    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
    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 Kettle, Suffolk, England
    |""""| ~ Lime plaster repairs
    / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc
    |____| 01359 230642
    Anna Kettle, May 10, 2005
  9. Charlbury

    Mike Guest

    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 ?
    Mike, May 10, 2005
  10. Charlbury

    bigcat Guest

    1:1:6 does a little, but not enough for Victorian brick walls, 3:1
    doesnt. Chalk does, granite doesnt. So not that simple.

    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.

    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.

    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.

    its one cause
    not always. cracks here that arent connected with blown areas.

    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.

    bigcat, May 11, 2005
  11. Charlbury

    Charlbury Guest

    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

    Charlbury, May 14, 2005
  12. Charlbury

    Charlbury Guest

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

    Charlbury, May 14, 2005
  13. Charlbury

    biff Guest

    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'.
    biff, May 14, 2005
  14. Charlbury

    bigcat Guest

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

    bigcat, May 14, 2005
  15. Charlbury

    bigcat Guest

    .... 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.

    bigcat, May 14, 2005
  16. Charlbury

    Charlbury Guest

    Charlbury, May 14, 2005
  17. Charlbury

    bigcat Guest

    Well, dont pay more than £6.50 for it. A bag of lime from the local BM
    can be mixed to putty and left to mature for a few weeks in a sealed

    bigcat, May 14, 2005
  18. Charlbury

    biff Guest

    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.
    biff, May 15, 2005
  19. Charlbury

    biff Guest

    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
    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.
    biff, May 16, 2005
  20. Charlbury

    biff Guest

    Well, I realise that you can use pozzolans to make lime set, but it
    takes on the undesirable properties of cement and loses its self
    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
    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
    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
    your average builder.
    How terribly true. We do have a great task in educating the building
    There are plenty of areas where modern materials can help with
    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.
    biff, May 16, 2005
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