matching (?) repairs

[charlie-ia]

im sorry i keep asking all these questions , but hopefully the quality of the questions is improving as im learning/doing more, and would really like to say thankyou to you all for your time, guidance and patience.
THANKYOU!

im a little unsure (just for a change) about matching repairs with the original materials. i can see if it shows, that colour is important just for aesthetic reasons, but if it doesnt show, does it matter?
so far we have done a little repointing in places that are going to be limewashed later. the stuff we have done is a bright grey, and the original is more of a dull brown.
contrastingly what about what ive heard called "honest repair" - we went on a lime course in malton, and the chap there had been using pieces of tile to repair broken/missing stonework, leaving them exposed to show that it was a repair rather than the original material. (i thought it looked rather nice too.)

i can see that if you repair using a different material, it will act in a different way (cement over lime will crack 'cos one moves and the other doesnt). fair enough. but what about when we have to use a different material? for example, we think we need to grout our wall. nhl5 has been recommended because lime woudnt set quick enough, but our mortar is mud. where does that leave us?

i have also read that repairs should be softer than the existing material. why? :? i know that the mortar should be softer than the stone, but should replacement mortar be softer than the existing mortar? (or just not harder than) and how do we achieve this when, as i have said, we have earth mortar?

its the general principal im having trouble getting my head round, the specifics are just for examples.

 

[JMartin]

Hi Charlie,

I can't offer much in the way of help to you as I am learning as I go along too but I know a builder told me last week that if you render on top of existing render then the top surface has to be weaker otherwise it will pull the bottom layer away from the wall and possibly the brick surface with it as it contracts when it dries.

I'm afraid though that that is the sum of my knowledge on this topic.

 

[charlie-ia]

makes sense, but the original in our house is lime plaster+ lime wash over mud mortar/earth plaster. ok, alot of the plaster is falling off, but it is original.

these are two short documents ive just read which explain why the man in malton was leaving his tile repairs exposed. interesting, but dont clarify much to me.
http://www.icomos.org/venice_charter.html
http://www.icomos.org/athens_charter.html

 

[Lady_Mari]

Charlie, I assume you have already read this about Earth Building & Repair from PPUK info pages.

http://www.periodproperty.co.uk/article032.htm

 

[NT]

If you have earth mortar surely the thing to point with is more earth mortar. Ditto for rendering.

The strength difference is to avoid stones or bricks breaking as the house moves, which old buildings with little in the way of foundations do to some degree. You want the mortar to break, not the brick. No need for repointing to be weaker than other pointing.


NT

 

[biffvernon]

I can't see a problem with lime pointing over earth mortar. That was a pretty common practice when earth was cheap and lime was expensive (no change there then) but gave better protection from being washed out by the rain. Use ordinary hydrated lime rather than NHL5 unless you are doing very exposed places like chimney flaunchings. It doesn't really matter how long it takes to set. If you don't want the bright white look of fresh lime add some earth to the mix or use very dirty sand.

 

[Mark]

I notice that Mike Wye's course descriptions cover mud mortar - maybe one of his courses?

I guess there is a lot more mud/cob about in devon than in Malton?

 

[biffvernon]

Malton? There was an article in Cornerstones, the SPAB Journal, a couple of issues ago about earth mortars in medieval buildings in Malton.

 

[charlie-ia]

we went on a tour of malton as part of our lime course. saw the most wonderful vaulted cellar all stuck together with only mud (York House). really opened my eyes

No need for repointing to be weaker than other pointing.

thanks for clarifying that. sometimes i need things spelling out. ("check that theres a lintle" was another pearl of wisdom i picked up on here once! )

we do intend to make mud mortar for where its needed. (mostly indoors)the lime in the cupboard was just a practice, and there was hardly any remaining mortar in the wall. the other side of the wall is a mix of mud and lime patches and minor cement repairs already. we,ve certainly improved things,last month he was putting his pinnings in in one room, and pushing mine out as i tried to fix the other side of the wall :lol: though its not finished. its beginning to look quite solid now and not so scarey. and the cement is beginning to leave the building!

we're going to mix more earth in next time, so hopefully that will blend the lime mortar we;ve already done, to the earth mortar at the edges. theres still quite a bit left to do. at 12mm (give or take!) a layer on 18" thick walls we're taking things steadily at a 2 layers a month.

i had read that page lady mari, but it was a while ago.

what about "honest repair" compared to "invisible repair?"

obviously you wouldent want it looking all patchy and has its limits , but i see that leaving signs of where youve been has its uses.

weve been throwing any left over lime at the kitchen wall to replace the thrown render outside.its not the same to look at at all and probably softer, but an easy way of using up leftovers. should we go to the extra effort of mixing it up to match whats there, or just say its an "honest repair" (otherwise known as bu***r it im tired) and limewash over it with the rest later on? the texture is pretty similar and will probably blend in nicely when its painted.

the houses in malton were a bit patchy. where the stone had failed the man had put in stacks of broken tile and left them showing. surely if he had finished them over with lime, them anyone doing future repairs would still find them, so why not cover them up? (it did look good though, so maybe he just liked it?)
and if youre going to do that, except for mechanical reasons,why bother to match anything? im being argumentitive now but im confused. he made sure the lime matched in every way he could and then put it round repairs that carefully didnt match :?

 

[chuckey]

The process of sticking things into lime courses is called garnetting. It is a local style in some places (don''t know where). In Carperby in Wensleydale the market cross has been "restored" using lime with garnets. A it looks awful and B, its the only example of garnetting I have ever seen. Is this a good thing to do? What its saying to me is "some over qualified restorer has tried out his idea on our cross" :twisted:
Frank

 

[Nemesis]

Galeting. See picture 24. It's a traditional building technique.


http://www.norwich.gov.uk/webapps/citywall/23/report.asp

Nothing at all to do with 'honest repair' showing the new work as being not trying to ape the old.

 

[biffvernon]

Galleting is usually associated with flintwork in East Anglia but this picture shows bits of ironstone in a sandstone wall in Surrey.

Garnetting is more of a textile thing.

 

[Nemesis]

Lovely! Ta for that pic!

 

[worms]

Interesting! I've seen this in Aberdeenshire, with slate chips inserted in the pointing in granite buildings from the first half of the 20th C. Looks pretty awful to me, but I might look at it in a new light if I thought it was based on a local tradition!

 

[Flyfisher]

I also thought it looked pretty awful, so I assumed there must have been a good reason. A quick Google found this explanation:

Gallet - (galleting, garnetting or garreting)
- chip or spalls of stone, brick etc pressed into mortar joint. Garnetting or garreting are two regional variations (Galet is French for a small river washed pebble). Can be decorative but purpose is primarilly to reduce amount of mortar required, and hence the possibility of shrinkage, prior to the wall being rendered. Cherry cocking is essentially the same process, but the stones are inserted in a more even and regular pattern to achieve a decorative effect

 

[Nemesis]

http://www.genealogy.guernsey.net/LRoyindx.html

I think it very decorative, adds to the texture of a wall.

(galet - biscuit it says...)


http://www.wordwizard.com/ch_forum/topic.asp?TOPIC_ID=19081

In his book on the Brecklands, W. G. Clarke says that Galleting, i.e., insertion of pellets in the mortar joints, may be seen at Swaffham, Narborough, Beechamwell, Gooderstone, Northwold, Methwold, and Feltwell. Red-brick, tile and flint-chips are used at Gooderstone; cinders at Northwold; red-brick, cinders, quartzite pebbles, flint-flakes and carrstone pellets at Feltwell. Galleting is done partly to prevent the pointing from weathering and partly to add to the beauty of the building.

 

[charlie-ia]

the thread on modern sensibilities is answering a lot of my questions.
i do keep finding references though about new mortar needing to be softer than the origonal mortar. none of the articles say why though. could it be purely so that the modern stuff is sacrificial, and will drop off in preference to damaging the historic mortar? or could there be another reason?

 

[Nemesis]

Mortar needs to be softer than the original building material - is that not what it means?

 

[chuckey]

Nemesis, am I forgiven?
Charlie, I think the theory is that if the building settles and/or the old mortar gives way, you don't get the front edge of a brick or stone sitting on a narrow strip of really hard mortar that might flake the front of the brick/stone.
Frank