if i use hydrated lime in my mix for exterior rendering to give me more time to work with it , assuming i use a mix of 4.1.1 , how do i integrate the lime ... do i mix it with water first and leave for a number of days or do i just shovel it in to the mixer with the s and c ... or is it easier just to use a retarder [i dont mean the labourer ;D]also on this job the original scratch coat is still intact ,how will i prep it for the top coat .. will i need to re- key [with an angle grinder ] and what about suction . will i need to apply liberal amounts of pva .. many thanks
hydrated lime
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Lime in a S&C mix is make it the material easier to spread and if your looking to slow the setting process down you will need a labourer (sorry retarder).
I take it from your question that you have been asked to re-render on top of a previous coat of rendering. I personally would have serious concerns about doing this type of work and if I was forced to I would make sure that NO guarantee was given or expected, and by the way this would be in writing. If you do go down this route ensure that you use a suitable SBR which is not effected by wet/damp conditions.
I take it from your question that you have been asked to re-render on top of a previous coat of rendering. I personally would have serious concerns about doing this type of work and if I was forced to I would make sure that NO guarantee was given or expected, and by the way this would be in writing. If you do go down this route ensure that you use a suitable SBR which is not effected by wet/damp conditions.
the use of lime in a mix will act like a plasticiser and give the mix greater elasticity when set but the down side is the resulting material is much softer than sand and cement so in high trafic areas it is not suitable. Also your ratio 4.1.1 seems to be a little strong to me you need to up the sand content to at least 6. By using 4.1.1. you may have problems with cracking due to shrinkage because your ratio is the equivolent of 2.1 ,In my experience using lime advances the initial set of rendering material which would cause you problems if you are wishing to re***d the setting capabilities of the rendering material, finally take Garys advice with regard to the first coat. The fact you feel that you need to give it more key would start my alarm bells ringing that with out suction issues. [smiley=undecided.gif]
nice one lads.. understand now about the integration of the lime and thanks for the ratios. im not too sure about the original scratch coat , the problem is i cant get it off . its absolutley solid. what issues will arise if i have to leave it in situ...even with a new key will there be problems with adhesion?...or is it just simply not worth it and should i do everything to get it off ?..... many thanks
If you leave it on its a fair bet that you will get shelling between the coats, I would also check that the rendering that is on as not already started to shell from the background. It can shell and yet at the same time be similar to granite rock LOL.
Does the job allow you to batten the walls out and fix on top of them?
Does the job allow you to batten the walls out and fix on top of them?
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