External lime plaster on straw bale wall

Lime plaster layers

Lime plaster layers

The sample shows all the layers of the external lime plaster over a straw bale wall:

1. (30cm -45cm) Straw bale of a density minimum 90kg/m3 made of wheat or rye straw

2. (0.5cm) Clay slip made of local earth and water. This layer is applied by hand, wearing thick rubber gloves to prevent scratching. Scratch marks are applied with a toothed metal trowel

3. (1-1.5cm) First layer of lime plaster made of hydrated lime (lime putty), coarse sand (0.5-4mm), clay and chopped straw. This layer is applied with metal trowel and scratched after application

4. (0.8-1.5cm) Second layer of lime plaster made of hydrated lime and coarse sand applied with wooden trowel and scratched after application

5. (0.3-0.7cm) Third layer of lime plaster made of hydrated lime and fine sand (0.4-1.3mm) and some fly ash to improve durability. This layer is applied with wooden trowel and smoothed with a wet sponge

6. Lime wash (2-4 layers)

You should give enough time for each layer to dry before applying next layer. Usually 48 hours for earth layer and 24 hours for lime layers. In the same time you must sprinkle some water with a mister just before application of a new layer. After application of lime plaster (3-5) you shouldn’t let the wall dry to quickly as it needs water to cure. In case of warm weather, you can cover the wall with plastic foil or sprinkle the wall with water daily. You should do it for at least first 10-14 days after the application of plaster to allow lime start curing properly. After that period you can paint a wall with lime wash. Usually, 2 layers are enough, but to get eye blinding white wall, up to 4 layers can be applied. Lime wash has a low opacity so you won’t see the final effect immediately. Wait minimum 2 days after the first 2 coats to see whether you need to apply more lime wash.

Posted in Lime, Lime Plaster, Straw Bale Tagged with: , ,