Lime Render

Lime render is a traditional, breathable plaster used for centuries on old buildings. Unlike modern cement renders that trap moisture, lime render allows walls to breathe and release moisture. This prevents damp issues, timber rot, and other problems often caused by moisture being trapped within the building's fabric. It's the ideal choice for renovating old homes and heritage properties.

The main difference is how they set. Non-hydraulic lime is a pure lime putty that sets very slowly by reacting with carbon dioxide from the air. It's soft, highly breathable, and flexible, making it perfect for internal walls. Natural Hydraulic Lime (NHL) contains natural impurities that cause it to set quickly with water. It's much harder and more durable, making it the best choice for exterior walls and areas exposed to dampness.

The right choice depends on your specific needs:

- For soft, historic masonry and internal walls: Use non-hydraulic lime. Its flexibility won't damage the delicate brickwork or stone beneath.

- For external walls or damp environments: Use a Natural Hydraulic Lime (NHL). The higher the number (e.g., NHL 5), the faster and harder the set, which provides more protection against the elements. A good all-round choice for most external work is NHL 3.5.

- For specific projects: Always consider the wall's material. The render should always be softer than the underlying masonry to avoid causing damage.

While the upfront cost of lime render may be slightly higher, it's often more economical in the long run. By allowing walls to breathe, it prevents expensive moisture damage, wood rot, and crumbling masonry, which are common problems with cement-based products. Using the correct materials on an old building saves you money on future repairs.

Proper preparation is crucial for success.

1. Remove any old, failed render, especially cement-based materials.
2. Clean the surface thoroughly to remove all dirt, moss, and loose particles.
3. Repair any cracks or voids in the wall.
4. Dampen the wall evenly with water using a spray bottle. This prevents the wall from drawing moisture out of the render too quickly, which can cause cracking and a poor bond.

Apply lime render in thin coats, typically no more than 15-20mm at a time.

1. The scratch coat: Apply the first layer firmly, ensuring good contact with the wall, then scratch it with a stick or render scratcher to create a key for the next coat.
2. Subsequent coats: Apply these once the previous coat has started to set but is still damp.
3. Finishing: The final coat should be applied thinly and floated to a smooth finish.

Lime render cures very slowly. A good rule of thumb is to allow one day of curing for every millimeter of thickness, but this can vary depending on weather. It must be protected from direct sun, wind, and frost. The key is a slow, steady cure to develop strength and durability.

Yes, but you must use a breathable paint or a limewash. Using standard modern paints like vinyl or acrylic will seal the surface and trap moisture inside the wall, defeating the purpose of using lime render in the first place. Limewash is the most traditional and effective finishing option.