Can you put lime render over cement render?

Can you put lime render over cement render? The short answer: No, you shouldn’t. Lime render and cement render are incompatible.

In our experience as your plasterers in Cheltenham and Gloucestershire, they work in fundamentally opposite ways, and combining them can lead to structural and aesthetic issues in your building. Here’s why:

Why Lime and Cement Don’t Mix

Lime render is breathable. It allows moisture to escape, helping a building “breathe” and reducing the risk of trapped moisture, which can lead to dampness or decay. On the other hand, cement render is dense and impermeable. It traps moisture, forcing it into the structure or pushing it to the surface.

If you apply lime render over cement render, the cement layer will block the breathability of the lime. This can cause the lime to fail prematurely, leading to cracks and flaking. Additionally, moisture trapped beneath the lime render can cause significant damage to the building fabric over time.

Why Lime Render Matters for Old Buildings

For older properties, particularly those originally built with lime-based materials, lime render is essential. These buildings rely on breathable materials to manage moisture. Replacing lime with cement or applying lime over cement disrupts this balance. The result? Rising damp, crumbling plaster, and even damage to the building’s structural integrity.

Using lime render ensures the building remains breathable and better protected. If the property was originally constructed with lime, it’s always best to stick with lime for repairs and maintenance.

Advantages of Lime Render

• Breathability: Lime absorbs and releases moisture, unlike cement, which locks it in.
• Sustainability: Lime is an eco-friendly material with a low carbon footprint.
• Flexibility: Lime is less brittle than cement, making it more resistant to cracking as buildings settle.
• Aesthetic Appeal: Lime renders offer a softer, traditional finish that suits period properties.

Precautions When Using Lime Render

Lime render is not dangerous but should be handled with care. During application, lime can cause skin irritation or burns. Wear gloves and protective clothing to avoid direct contact. Additionally, lime dust can be harmful when inhaled, so always use a mask and ensure good ventilation when mixing or applying lime.

What to Do Instead

If your property currently has cement render but needs restoration, it’s best to remove the cement before applying lime. A professional plastering service can safely remove the incompatible material and apply a proper lime render that supports your building’s health and longevity.

For expert help with lime rendering in Cheltenham, Gloucestershire, and the Cotswolds, contact us today. Our team specializes in preserving period properties with high-quality lime plastering.

FAQs

1. Can I repair lime render with cement render?

No, cement render is not suitable for repairing lime render. Cement is rigid and impermeable, while lime is flexible and breathable. Repairing with cement can cause damage to the original lime and the building itself. Always use lime-based materials for repairs.

2. How can I tell if my property has lime render or cement render?

Lime render typically has a softer, more natural finish with visible texture. It feels slightly powdery when touched. Cement render, on the other hand, is dense, smooth, and hard. A professional can help you confirm which material is used.

3. Is lime render more expensive than cement render?

Lime render can be slightly more expensive upfront due to the materials and expertise required. However, it’s a long-term investment. Lime reduces damp issues, prevents structural damage, and lowers maintenance costs, making it more cost-effective over time.