The mysteries of lime

by Richard
(Derbyshire)

I’m going to render & plaster the internal face of a brick wall in the lean-to conservatory in my garden. I decided to use non hydraulic lime as in the 1.1.6 cement lime & sand ratio shown on your web page (you have now got me hooked on lime plastering!). I would like to use hydrated lime putty instead of hydrated powdered lime.
The problems I have are. 1. Lime putty comes in litres and I can’t find out what ratio and measure of putty to use with the 1.6 cement & sand. Also would you still advise adding plasticiser along with the lime?
2. Your video on backing coats is brilliant but there is nothing on mix consistency as there is on your finish plaster. What should I look for?
3. I have looked at Limelite Whitewall One Coat as a finishing plaster. Would you rate it as a good choice or is there a better alternative.

Answer
1. When using lime putty you can measure it out with the sand by measures of volume - using a suitably sized container. No plasticiser will be needed.
2. Consistency of backing coat can be whatever you find usable and controllable. It still wants to be firm enough so that it peaks - but not too firm that much pressure is required to apply it to the wall. A cottage cheese like consistency would be a good average!
3. Limelite one coat is literally one coat and so can be applied directly to the brickwork, so no need for a backing coat, however it is not always easy for a beginner to master. if you are using a backing coat then lime putty will work well as a finish coat.