The application of the lime plaster is very similar to the application of cement stucco. A few precautionary steps MUST to be followed in order to achieve good results:
PROTECT THE WORK BY USING TARPS
Curing and suction control are the most important factors. The slower the curing, the better the result. It is important to use tarps, burlap, etc. to protect the work for several days from adverse conditions such as sun, wind and rain. If conditions become too excessive, it may become necessary to mist water on the walls.
MIXING TIME
For NHL 3.5, NHL 2 & NHL 5 (when adding your own sand), mixing a minimum of 10 minutes is required. Be very careful not to add too much water at the beginning. Measure the water carefully. The lime is going to hydrate slowly and too much water will result in a “slurry”.
NOTE: for Ecologic™ Mortar (premix, no sand needed) mixing time is five (5) minutes maximum.
TIME BETWEEN COATS
Wait a minimum of 10 days (or longer) between coats.
WET THE WALLS BETWEEN COATS
At the end of the day, the day before the application of a new coat (brown and finish) we recommend that you soak the walls to allow them to absorb as much water as possible. Do not have any water running or dripping down the wall at the time of plastering.
REWORK THE PRODUCT
NHL can be reworked up to 24 hours after application depending on the weather conditions. This is possible mainly because there is no cement in it.This is a huge advantage. If some cracking occurs in the brown coat, the applicator can mist the crack and close it up the next day, allowing for a flawless result. Drying conditions can reduce that window of opportunity so take advantage of it.
Although most of the steps we recommend are similar to the recommendations of the PCA or Portland Cement Plaster (Stucco) Manual, most of applicators do not follow these guidelines. The additives that are in Portland Cement compensate for these lapses, as well as improve productivity and workability. The lime that is specified on your project is called Natural Hydraulic Lime or NHL. The European Norm EN 459-1 specifies that NHL cannot contain any additives or any additional materials. It is considered a pure and natural product. Consequently there is nothing in NHL that will help to compensate for lack of workmanship or allow the contractor to “cut corners”. The material tells the applicator how to work, not the other way around.
PLEASE, ALWAYS CONSULT – www.LimeWorks.us FOR DETAILED INSTRUCTIONS.
Please do not attempt to apply lime plaster without reading the documents contained in the section best describing your project type.
I need make large amount of lime stipple plaster for historic restoration of a massive home in NH. Horsehair plaster on wood lath with heavy stipple walls and ceilings. Only kitchen, bathrooms, and pantry are smooth. 1904 built with back plaster on inside of exterior sheathing. Dead air space for insulation. Ratio of Lime, plaster, sand. Going on 1/2” level 4 drywall ceilings with a primer and adhesive
Hello Jay,
Thanks for your questions. First, please note that lime plaster behaves differently than modern gypsum plasters. You should not use any modern primers or adhesives meant for gypsum plasters (e.g. drywall mud, joint compound, structolite, diamond veneer, etc.) with lime plasters as in our experience they can affect the bond. Going over drywall or existing gypsum coatings, we recommend you instead use a thin coat (1/8″ or so) of our Ecologic Takcoat material (https://www.limeworks.us/product/ecologic-takcoat-platinum/).
For your stipple coat, please see our General Installation Guidelines for how to make a lime-based plaster using NHL (https://www.limeworks.us/product-documents/#1572635128546-850d1be7-7faf). You’re going to be using a coarse sand and mixing it with either NHL 3.5 or NHL 2 in a ratio of 1 part lime to 2 parts sand. The sand should be clean and free of a significant amount of very fine material. Stipple coats are a lot like exterior stuccoes as well, so you may want to also review our NHL stucco guidelines on the same page I linked above.
These are the basics. I generally try to avoid going into specifics in comments because I don’t want people to apply advice for your project inappropriately to theirs. So, if you need more assistance, please give us a call Monday-Friday 8:00AM to 3:00PM Eastern and ask to speak to “Gene” our in-house plasterer. He can help you walk through the steps in more details and also provide some tips and tricks you may find helpful.