Exposed Cotswold Stone Wall Needs Sealing

[bigcat]

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

NT

[bigcat]

... 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

[Charlbury]

Thanks

I think I'll be going for a delivery of Lime Putty from these guys:

[bigcat]

can be mixed to putty and left to mature for a few weeks in a sealed container.

NT

[biff]

I would, and do, happily pay more than =A36.50 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 =A33 more expensive than at B&Q. Hmmm.

[Stuart Noble]

I'm perfectly willing to debate issues constructively but turning the clock back 100 years and refusing to budge doesn't constitute debate in my view. And constant references to a website where people gather to congratulate themselves on their good taste doesn't either. Can *you* explain how lime can be made water resistant without losing the properties which distinguish it from cement? Let's debate it!

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[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.

[Stuart Noble]

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.

So in a 9" wall driving rain passes through the mortar and ends up where? Does it evaporate to the inside?

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.

I can only say not in my experience. I have re-pointed loads of brickwork with cement mortar but I have combined it with modern polymers. They do not affect the appearance but seem to give it added flexibility. Certainly none of it has cracked over 5-10 year periods.Without modification, sand cement mortars do not reliably adhere to old brickwork.

But anything on the plaster will be damaged, which rules out wall coverings.

All very well but, in the real world, your average punter has to deal with your average builder.

There are plenty of areas where modern materials can help with conservation. The Victorians couldn't have preserved the Mary Rose.

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[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.

[Mike]

I was agreeing with everything you said wholeheartedly until you got to this. I know a lot of people share your view but my counter argument is that a failed joist should be removed and an exact copy made in the same wood. Yes it will take many years for it to age enough to look the same but my belief is that you have a more exact preservation of the original building for those to come in the future and will require less work in future to keep it so. Resin bonded joists could be a real pig to remove when the time does come to replace them when they fail completely.

After all would you try to repair a failed brick or try to find a similar one, preferably from that period ?

[Anna Kettle]

Pozzolans form very weak cements, like the early cements of 150 years ago. Modern cements are about 20 times as strong

Driving rain hits the wall but only makes it through the first 1mm or so, and then the surface layer is waterlogged and no more rain can get in. Water vapour moves through the mortar much more freely

Indeed that is true. But can you guarantee that water won't get in? Especially on an old house without rigid foundations?

Thats interesting. You mean Febmix or suchlike? Lime is sometimes used as a plasticiser in cement render too. Do you think it is less successful, or is Febmix just more convenient for you?

Perhaps it is time for wallhangings to come back into fashion!

Anna

~~ Anna Kettle, Suffolk, England |""""| ~ Lime plaster repairs / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|

01359 230642

[Charlbury]

Another suggestion has been made:

and delivery. I >personally would not use this route. Although what you have been told is correct, I use >silicate fixative to do a much better job with no discolouration. Very breathable too.

so don't get it on your >skin or in your eyes and you cannot use limewash after using it.

Does anyone have any experience with this or a view on the suggestion?

Thanks again

Steve

[Mike]

The price of hydrated lime does appear quite random. I have a line of plastic dustbins used to mature lime putty which I make from hydrated lime. It needs several months for best result. I also get ready made putty from Bleaklow (near Buxton - proper Buxton lime) just down the road but for most applications there is little difference in the final result. I find the choice of sand far more critical to a good or bad result and go far and wide to look for better types. Three years ago Wickes sharp sand was superb but then of course they changed quarry and couldn't/wouldn't tell me where they used to get it.

[biff]

Yes, Mike, I agree about the joist ends. It just seemed a simple example to illustrate that there may be some good uses for modern materials. Not a very good example, on reflection. There are better examples in Richard Oxley,. Survey and Repair of Traditional Buildings: A Conservation and Sustainable Approach. Donhead 2003

There's some information about sodium silicate or waterglass and its effects in cement here:

on nearby pages.

[Stuart Noble]

I don't really buy this. I've seem many examples where rain comes straight through the wall summer or winter, which would seem to rule out condensation.

Yes but nothing you can apply to the outside of a house is as effective as a plastic mac. Cement behaves like the goretex, keeping water droplets out but allowing vapour to pass outwards.

I don't think the humble abodes I work on are likely to fall in that category. Mostly people who just want to protect their families from damp.

This is all a bit nerdy isn't it? People first, conservation where possible, but not at any cost.

Now this simply isn't true. Most houses are centrally heated and have adequate ventilation. If human activity produces condensation on the walls, then one or other must be lacking.

On the odd occasion that's true. Mostly it's just driving rain hitting porous walls.

IMO the restoration culture is essentially fuelled by money. What people perceive as heritage fetches more money in the housing market.

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[Stuart Noble]

I don't think one should lose sight of the fact that houses are just places where people live. The rest is just fashion.

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[Stuart Noble]

I wish I could believe that. I expect it's true in ideal conditions where the overall depth of mortar is several inches but, in the realms of patching up old brickwork, the thickness is likely to be less than an inch. IME this doesn't survive the first downpour.

I'm not a great believer in rising damp in brickwork but I guess it's more relevant in your neck of the woods. I've seen walls where the lower part was damper than the rest but that doesn't mean the damp is rising. Usually it's falling damp.

brickwork

Feb make an awful lot of additives, including SBR, which increases the flexibility and adhesion of cement mixes. Allows much thinner layers to be applied.as a render for example. I know plasterers use lime in cement renders because it makes the mix more "buttery" (as one described it). A true plasticiser reduces the amount of water required to get a workable mix, which in turn results in a stronger end result.

Wow, that would make makeovers even faster.......

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[Mike]

It's just the one where restoration people get very entrenched on what is the correct way. They were "repairing" the joists on one of the Grand Designs recently under the orders of the conservation officer and I was literally screaming at the TV much to the wife's amusement.

Other thing I hate are those tie-rods through the building pulling it back together. The historic way to do it would have been to demolish and rebuild the wall in the same materials but this seems to have become a total no-no with COs.

Yes - excellent book. Highly recommended to anybody starting work on an old building.

[Anna Kettle]

There is historical precedent for tie rods though. I have a 18thC tie rod in my house. If I didn't, it wouldn't be here now

Anna

~~ Anna Kettle, Suffolk, England |""""| ~ Lime plaster repairs / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|

01359 230642

[biff]

I have a 18thC tie rod in my house.

So have I. I suppose, Mike, you thought the Leaning Tower of Pisa should have been demolished and rebuilt upright instead of having its foundations supported. :-)