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Crumbling stone cills |
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| message from Martin Pentreath on 17 May 2004 |
The exterior stone cills on many of my windows are in pretty poor shape -
the surface of the stone seems to have cracked and crumbled, and been filled
by what looks like some sort of caulk before being painted. Anyway, the
whole lot is in need of stripping back and redoing now. What's the best way
of patching up the crumbling masonry? And how do I need to prepare it before
I put on whatever I'm going to put on?
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| Dave Plowman replied to Martin Pentreath on 17 May 2004 |
If they're going to be painted, rip them out, knock up some shuttering,
and cast reinforced concrete ones in their place.
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| BigWallop replied to Martin Pentreath on 17 May 2004 |
If they are in that bad a state, then your best bet is to get a stone mason to make
new one for you. Just think how old the property is and how long the original ones
have lasted. Patching over patching is never a great idea and stone is not really
that expensive. Makes for a better job and peace of mind.
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| Nick Brooks replied to BigWallop on 18 May 2004 |
Soft stone like Bath stone is very easy to work. It can be cut with an
old hardpoint saw and chipped away very easily with a cold chisel.
I recently repaired a damaged stone fireplace by cutting out all damaged
material with a chisel back to a square surface then letting in blocks
cut by hand.
Use stone dust ( from the sawing) and white cement ( or lime putty) for
the fixing and pointing.
Not nearly as difficult as it sounds and very satisfying
Nick Brooks
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| Lobster replied to BigWallop on 18 May 2004 |
Rather than commissioning a stone mason (arm and leg?!) it would be
worth looking in a local architectural salvage yard first; you may
well find an exact match quite easily. Though I must admit if it was
me, I'd probably try a bodge repair first and try to wring another few
years life out of it.
I've tried the car body filler trick which somebody else mentioned;
worked not badly (assuming you'd over paint it. Certainly you ought
to scratch out any old filler first though, and try to get back to a
firm substrate.
David
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| stuart noble replied to Martin Pentreath on 18 May 2004 |
If they're going to be painted, a skim with car body filler works well.
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| Carnie replied to stuart noble on 18 May 2004 |
Would your answer be different in a listed building? Replacing like
with like (stone with stone) seems preferable to introducing a new
material like car body filler. However, many purists would say that
introducing replacement materials (even of the same type) destroys the
patina of the building. The fact that the stone is unpainted makes
the selection of materials critical.
I don't ask this idly, I've been looking at some 14th century cills
that are so badly eroded that wind and rain are getting in. Something
must be done, but what is the best solution, historical interest and
practical considerations taken into account? Carnie Parkin
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| Anna Kettle replied to Carnie on 19 May 2004 |
In conservation you aim to keep as much of the old as possible and
also aim to make any repairs reversible so they can be undone if it is
later discovered that they are doing damage.
If you are English Heritage or the National Trust with oodles of money
then this is implemented rigorously. Conservation officers hopefully
realise that mere mortals have limited budgets and compromises have to
be made
But if leaving it alone is causing it to decay then purists say that
introducing replacement materials is necessary or it won't be there
for much longer
Either insert slips of matching stone or use a lime mortar with
aggregate like the original stone. Don't try to build it up to the
level that the stone was when new, just add enough stone/mortar to
stop the wind and rain getting in. Either of these options will
satisfy the conservation officer.
You might want to look at the SPAB (Society for Protection of Ancient
Buildings) web page
www.spab.org.uk
SPAB are the fount of all knowledge about such things
Anna
~~ Anna Kettle, Suffolk, England
|""""| ~ Plaster conservation and lime plaster repair
/ ^^ \ // Freehand modelling in lime: overmantels, pargeting etc
|____| www.kettlenet.co.uk 01359 230642
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| stuart noble replied to Carnie on 18 May 2004 |
I think the purists should come down from their own backsides and look at
adapting/improving modern materials. There is no reason why a polyester
resin with crushed stone aggregate shouldn't look pretty damned good.
The materials used to preserve The Mary Rose weren't exactly authentic but
it was rightly considered a worthwhile compromise.
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| MBQ replied to stuart noble on 19 May 2004 |
Well said! If the economics of car body filler v stone replacement
were the same in the 14th C as they are now, I know which would have
been used!
If the purists had been in on the act a bit earlier we'd all still be
living in mud huts.
MBQ
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| Dave Plowman replied to MBQ on 19 May 2004 |
What - you'd use car body filler on natural stone? I'd also not guarantee
how long it would last exposed to sunlight. Many types are also porous.
The problem often comes with painting stone IMHO - it seems to make it
deteriorate much more quickly - although it still takes many years.
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| stuart noble replied to Dave Plowman on 19 May 2004 |
Never had a porous one. They use polyester to make ships. The basic
properties are plenty good enough for this application.
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| Dave Plowman replied to stuart noble on 19 May 2004 |
The 'bulk' in some fillers is or was a form of talc. And all body repair
manuals still mention making sure it's properly dried out moisture wise
before painting.
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| stuart noble replied to Dave Plowman on 20 May 2004 |
I can't understand that because the resin contains no moisture, and cures
rather than dries.
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| The Natural Philosopher replied to stuart noble on 21 May 2004 |
The resin won't not cure, it just won't stick.
To get best adhesion to porous surfaces you need _dry_ crumble and a
runny resin. It is possible to thin epoxy etc with acetone or similar,
and carry it into pores. That stabilises the crumble. Then you can build
up the shape with filler later.
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| stuart noble replied to The Natural Philosopher on 21 May 2004 |
It does need a little persuading sometimes. If you quickly work it with the
dust, it becomes part of the aggregate and sticks fine. You only need
prevent the dust acting as a barrier. A quick hoover
You can thin polyester with acetone or, better still, styrene, thought the
latter is hard to get hold of. Ordinary fibreglass resin is quite viscous
but, because of the longer curing time, it generally soaks well into porous
surfaces.
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| Dave Plowman replied to Carnie on 18 May 2004 |
Replace them with identical stone. That's what they do on cathedrals, etc.
You're not changing anything - merely doing maintenance.
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