How to Do Lime Plastering

Using lime plaster to finish and protect exterior walls has been a common practice for centuries on homes or outbuildings made of rubble, stone and even wood and brick. Readily available, lime plaster creates a moisture-proof barrier that lasts for years. Plastering a new wall or restoring an old one takes some know how and a bit of planning.

Difficulty: Challenging

Instructions

Things You'll Need:

• Aged lime plaster
• Trowel
• Lathe scratcher

1. Purchase lime plaster that is at least 3 months old; 6 month plaster is better but difficult to find. Aged lime plaster has had time to slake and won't be prone to lime eruption once it dries.

2. Prepare the wall by removing any loose dirt, grout or old lime plaster. Make the wall as smooth as possible to ensure proper bonding and easy raking.

3. Fill any deep holes or cracks with lime plaster before you begin the first coat. Smooth the area and allow drying for several hours. Place small rocks in larger holes or gaps as filler.

4. Use handfuls of plaster to begin the first coat and force it into every crack with as much pressure as possible. Smooth out the first coat with a trowel making the finish as flat as possible.

5. Check to see if the first coat is dry enough by pushing against it with your thumb. It should resist denting but still be easily scratched with a fingernail. Score the plaster using a lathe scratcher. Create a diamond pattern across the surface so the next coat is able to bond.

6. Wet the previous layer and continue adding coats with a trowel until the surface is flat and smooth. Score the final coat with a pattern of your choosing or leave it flat if desired.

Resources

• Lime plaster supplies and support