Roundtower NHL 3.5 Fine (Premix)
Roundtower NHL 3.5 Fine is a ready-mixed lime mortar manufactured from Natural Hydraulic Lime (NHL 3.5) and fine kiln-dried sand, blended in a controlled factory environment to provide a consistent, breathable mortar for fine pointing, plastering, and finish rendering applications. Supplied in a pre-blended 2:5 lime-to-sand ratio, it removes the need for on-site batching while maintaining the durability, vapour permeability, and workability associated with NHL 3.5 mortars.
Designed for both traditional and modern breathable construction, NHL 3.5 Fine offers greater strength and weather resistance than NHL 2 mortars while producing a finer finish than coarse premixed mortars. This makes it particularly suitable for fine pointing, smooth render finishes, conservation work, and exposed masonry where both durability and appearance are important.
Technical Data
| Property | Value |
|---|---|
| Product Type | Ready-Mixed NHL 3.5 Lime Mortar |
| Binder | Natural Hydraulic Lime (NHL 3.5) |
| Mix Ratio | 2:5 (Lime : Sand) |
| Aggregate | 2mm Kiln-Dried Sand |
| Yield | Approx. 13.5 Litres per 25kg Bag |
| Render Coverage | Approx. 1.4m² @ 10mm Thickness |
| Brick Coverage | Approx. 25 Bricks per Bag |
| Water Addition | 4–5 Litres per 25kg Bag |
| Open Time | Minimum 8 Hours (Weather Dependent) |
| Standard | BS EN 998-1 & BS EN 998-2 |
| Packaging | 25kg Bags |
| Vapour Behaviour | Breathable & Vapour Open |
Key Benefits
Ready-Mixed for Consistency
Factory-controlled blending ensures a consistent mix ratio throughout the project, reducing variability and improving reliability compared to site-mixed mortars.
Breathable & Vapour Open
Allows moisture vapour to move naturally through the wall structure, helping masonry dry out while reducing the risk of trapped moisture and damp-related issues.
Fine Finish Capability
The fine aggregate grading makes NHL 3.5 Fine particularly suitable for:
- fine pointing,
- smooth render finishes,
- plastering,
- and decorative lime work.
Increased Durability
The NHL 3.5 binder provides greater strength and weather resistance than NHL 2 mortars, making it suitable for exposed elevations and external applications.
Compatible with Traditional Masonry
Provides a balance of strength and flexibility, making it suitable for:
- stone masonry,
- historic brickwork,
- conservation projects,
- and traditional solid-wall construction.
Cement-Free Construction
Contains no Portland cement, maintaining compatibility with traditional building materials and breathable construction methods.
Typical Applications
- Fine pointing stone masonry
- Fine brick pointing
- Lime plastering
- Finish render coats
- External lime rendering
- Heritage restoration
- Conservation projects
- Exposed masonry repairs
- Breathable new-build construction
Why Use NHL 3.5 Fine?
Roundtower NHL 3.5 Fine combines the convenience of a ready-mixed mortar with the balanced performance of NHL 3.5.
Compared to NHL 2 Fine, it offers:
- increased durability,
- improved weather resistance,
- and greater compressive strength,
making it better suited to exposed locations and external work.
The fine aggregate grading makes it particularly suitable for:
- smooth render finishes,
- detailed pointing work,
- decorative lime finishes,
- and fine plastering applications,
while still maintaining the vapour permeability required for breathable wall construction.
For projects requiring a stronger breathable mortar with a refined finish, NHL 3.5 Fine provides an effective solution without compromising compatibility with traditional masonry.
Typical Applications by Use
| Application | Recommended Use |
|---|---|
| Fine Pointing | Narrow stone and brick joints |
| Finish Rendering | Fine float coats |
| Lime Plastering | Internal and external breathable plasterwork |
| External Masonry | Exposed elevations |
| Conservation Work | Heritage and listed buildings |
Installation Overview
1. Surface Preparation
Substrates should be:
- clean,
- stable,
- free from dust,
- and appropriately dampened before application.
2. Mixing
Add approximately 4–5 litres of clean water per bag and mix thoroughly. Allow the mortar to stand briefly before remixing and application.
3. Application
Suitable for:
- fine pointing,
- plastering,
- finish rendering,
- and decorative lime work.
4. Protection & Curing
Protect fresh work from:
- frost,
- heavy rain,
- rapid drying,
- and direct sunlight during curing.
5. Storage
Store dry, off the ground, and protected from moisture prior to use.
