rendering cotswold stone

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mistersmooth

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alrite lads-looked at a job last night-render over cotswold stone.the stonework is probably 20 yrs old and sticks out like a sore thumb next to the older part of the building(listed)having only ever rendered brick/block b4 is there anything i need to know-bonding agents etc.cheers for any advice u can give
 
External ? Is the building of solid stone construction ? if the anwsers yes to both then its nhl render for me
 
so that,ll be non hydrated lime then?what ratios would i want?do i need any prep-rendaid for example?and finally i reckon its gonna want a couple of scratch coats-what sort of time should i leave between coats-sorry to sound a bit dumb but im used to housebashing
 
Firstly might want to run it by the customer as there is a BIG difference in cost , hydraulic lime render is a total different animal to s&c rendering not in technique but in the way you go about it , you have to protect it from the elements for 48hrs after you have finished you allow up to 7 days in between coats, the ratios are easy 2-1 sand to lime washed sharp in the scratch coats and soft washed in the top coat , you scratch in a diamond patten not like on normal outside render the lime has different strenghts 5.0 ,3.5 and 2.0 if there signs of damp use 5.0 for the first coat then 3.5 or 2.0 on the other coat finish with a wood float only rule the second coat if you do three coats keep thicknesses to around 10 - 15 mm per coat also use pig bristles in the scratch coats about 2-3 bundles per mix , mix each gauge for around 20 Min's stop let it stand then mix again , never over soak the background before render a light spray is better . If you have a local lime supplyer go and see them for prices and advice but your looking at around £55 per meter plus mats hope this helps.
 
thanks church-blimey a little bit more to it than i or the customer thought-gotta say not entirely comfortable about going over stonework(seems a shame)i think the customer would be happy enough for just sand/cement although planning have stipulated a similar colour to adjacent stone(possibly pigment+white cement)im unsure as to suction/bonding issues as cotswold stone is almost like sandstone and i dont want any falling though his very expensive conservatory roof!if this looks to be likely then rib lath maybe?any advice would be very much appreciated
 
I know what you mean mate buts that's the trouble with old solid buildings , using modern materails and bonding agents etc is a bit of a mine field and what you may get away with short term may cause problems long term, you could use rib lath and s&c render but you are restricting the buildings ability breathe and stop it doing what it was designed to do...... fook it ...i dont know my head hurts now ;D
 
arrgh! been following this one with interest, church, i'm rendering the inside of a mates stone farmhouse in france next week. i was just gonna sbr slurry it and render as normal, do you reckon i'll get away with it?
 
whenever I have used hydraulic lime i have scratched as normal ...... whats the idea of the diamond scratch then church ???

Rich
 
Pug ,two coat render no skim ?

Richard , its for a key as normal but the diamond pattern allows the moisture to escape from the next coat.... like a guttering down pipe sort of thing ;)if you scratch horizontally it holds the moisture in then it shrinks and cracks more
 
OK mate the way i see it , the sbr will act as a bonding agent yes but it also act as a tanking which will stop air and water ingress which is fine if thats what you need...... but if you dont control the suction from the stone with water and use lime in both coats and a small ammout of plastersizer
 
church said:
Pug ,two coat render no skim ?

Richard , its for a key as normal but the diamond pattern allows the moisture to escape from the next coat.... like a guttering down pipe sort of thing ;)if you scratch horizontally it holds the moisture in then it shrinks and cracks more
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I see thanks church.

Quite a few years back we were on a job using hydraulic lime and Hydrated lime the lad that was doing the mixing couldnt read and for the whole day was using the wrong lime ...... few days later we realised and spent the day brushing off the render as it had turned to dust . dopey t**t
 
you think i'll get away without the sbr? thing is i'm not sure what sort of stone it is, when i asked my mate he said "err, its just stone" was gonna do 5;1;1 scratch coat 6;1;1 top coat
 
Pug said:
you think i'll get away without the sbr? thing is i'm not sure what sort of stone it is, when i asked my mate he said "err, its just stone" was gonna do 5;1;1 scratch coat 6;1;1 top coat
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Sounds good i suppose you really need to make your mind up when your at the job .... do you need a hand to carry your suit cases ?
 
No bullsh*t it's a shame you haven't done the Flexcement course because you could have replicated the older stone no problem at all. There is a very easy antiquing method and you can also replicate efflorescence, it is even possible to replicated granite including the quartz
 
hes an old mate but he does have some funny ideas! the stonework inside looks really nice (from the photos) i offered to repoint but he wants it rendered! getting paid, fed and drunk for a week, who am i to question him? ;D

will be in touch though stone!
 
A guy from Alton asked me to replicate cotswold stone on his bungalow after extending it, when I told him how easy it was he is booking in for a course. The most common brick in the UK is a wire cut, I was asked to replicate them. I thought about it for a while and then come up with the solution, to get the texture I used an old cement covered roller and for the wire cut I used a bent coat hanger, perfect result. It's just so easy.
 
After these May courses I will have 35 installers plus national paving companies use a lot. I have had nearly 800 hits on my website this month and loads of enquiry's and I haven't got the installers to cover the work in various area's. There are over 60million people in this country and most of them have never heard of it when they do there is going to be plenty of work for all the installers.
 
Pug "St Astier" are a massive French manufacturer of N.H.L. (Natural Hydraulic Lime) might be worth looking at their website.
Lucius.
 
thing is lucius, i've got 6 days to do all internals downstairs, not an issue with s+c, not gonna happen with nhl! he's got customers lined up to rent it for holidays in june so he just wants it finished, thanks for the info though.
 
just spent 3/4 of an hour on that website lucius! got shed loads of info on lime mortars, worth a look for anyone using it, cheers mate
 
with old buildings that breathed and the moisture was evaporated inside would it not hurt to use modern methods .........especially riblathe so it wont crack? will it affect it structually?
 
You need to be careful if the building is listed or in a conservation area, the chemicals in the cement can erode the stone causing damage to the stone and ultimate failure to the render, this is where the lime render comes in. Would be interesting to use the K rend product, it's always a bit of a 'ERMMM' when doing stone work, also can the K rend be used to replicate stone for sandstone repairs etc? I normally use lime sand & pigments and match by eye.
 
Yeh Pug only looked at the site the other day after a couple of years and its definitelycome on with new products, finishes, colours etc glad it was of interest. Unfortunately Spunkey no one has come up with anway or material to match the performance of the original lime morters on older buildings all modern materials just seem to cause so many problems i live in a medieval town that has been ruined by the misuse of S+C over the years, when i was in the U.K.i maintained a country estate for part of the year and the biggest problem was repointing of 18 +19 century red brick houses in S+C it had totaly ruined them with bricks spalling everywhere because S+C is to strong and permeable dosent allow the wall to breathe from the joints and eventualy cracks because of climatic movement lets water in and when it freezes blows taking some of the brick with it.
Sorry got on one then this is a plastering forum not bricklaying.
Lucius
 
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