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?
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.
If they're going to be painted, rip them out, knock up some shuttering, and cast reinforced concrete ones in their place.
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
If they're going to be painted, a skim with car body filler works well.
What sort of stone is it?
J.B.
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
Replace them with identical stone. That's what they do on cathedrals, etc. You're not changing anything - merely doing maintenance.
Sorry, it's covered in paint and filler, and I don't think I would know one type of stone from another even if it wasn't!
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.
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
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
Anna
~~ Anna Kettle, Suffolk, England |""""| ~ Plaster conservation and lime plaster repair / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|
"stuart noble"
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.
Never had a porous one. They use polyester to make ships. The basic properties are plenty good enough for this application.
In article , stuart noble
I can't understand that because the resin contains no moisture, and cures rather than dries.
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.
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.
Thanks for all the advice, I've done the first cill now. My house is of no particular historical value, just an 1880 terrace. Finances prevented me following the counsels of perfection involving stone masons. Instead I just hacked off all the crap, and got back to sound stone (which incidentally was of a yellowish tint, and made up of lots of layers in the same way as slate). I used a whole 2.5kg bag of quick set cement and built the cill up to where it should have been. It's ready for painting and looks fine now, and seems to be very solid. Only the onset of winter and some freezing water will tell whether it's actually any good, but it cost £2.79 and took
30 minutes, so I've not got much to lose.Here's the stuff by the way
Only another eight cills to go.
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