Sovereign RenderMix - Render Additive & Waterproofer

Health & Safety Recommendations

When working with Sovereign RenderMix, it is essential to observe appropriate health and safety measures. Wear suitable personal protective equipment (PPE) including gloves, goggles, and protective clothing to prevent contact with skin and eyes.

Avoid inhaling dust from cement and other dry components during mixing. Ensure adequate ventilation when working in enclosed spaces. Consult the product label and the Safety Data Sheet before use for specific health and safety guidance.

Sovereign RenderMix should be stored in a secure, frost-free environment between +5°C and +25°C, away from children and incompatible materials. Do not eat, drink or smoke while using the product.

Substrate Suitability

Sovereign RenderMix is designed for use on masonry substrates requiring re-rendering after the insertion of a chemical damp-proof course (DPC). The substrate must be sound, stable and capable of supporting the weight of the render system.

Do not use Sovereign RenderMix in structural concrete, floor screeds or any cementitious mix intended for load-bearing applications. It is specifically developed for walls affected by rising damp and should not be used in areas subject to high water pressure unless tanking is applied.

This product is not suitable for lime-based mortars or gypsum-based substrates.

Surface Preparation

Before rendering, remove all timber skirting, wall fixings, dado rails, radiators, and any other surface-mounted elements that may obstruct application.

Existing plaster should be completely hacked off back to bare brickwork to a minimum height of 300 mm above the last evidence of damp or to at least 1 metre above the inserted DPC, whichever is higher. All loose or friable material should be removed, and mortar joints raked out to provide a mechanical key.

If dry rot is suspected or identified, appropriate remedial works must be undertaken, including treatment of the area with Lignum Pro M50 Masonry Biocide. The prepared surface must be free from dust, oil, salts and other contaminants that may affect adhesion.

The substrate should not be saturated prior to rendering, but lightly dampened if excessively dry to prevent premature drying of the render.

Mixing

Sovereign RenderMix must be shaken thoroughly before use to ensure even distribution of active ingredients. Add 175 ml of RenderMix per 25 kg of cement. This concentrate must be diluted in the gauging water and stirred well before being added to the dry sand and cement mix.

If mixing smaller quantities, reduce the amount of additive proportionally. Avoid excessive mixing times, which can affect the consistency and performance of the render.

Use only CEM I Ordinary Portland Cement; blended cements such as CEM II to CEM V, masonry cements, or high alumina cement must not be used. Washed sharp sand should be used, free from salts and other impurities. Do not add any other admixtures to the mix.

Application Method

First Render Coat

The first render coat should be applied at a thickness of 8 mm to 12 mm. The mix should consist of 3 parts washed sharp sand to 1 part Ordinary Portland Cement, incorporating RenderMix at the specified dilution.

Apply the render using firm pressure to ensure full contact with the substrate. Use only the minimum amount of gauging water required to achieve workable consistency. This promotes a dense and durable render coat.

As the initial set begins, scratch the surface horizontally or diagonally to create a mechanical key for the second coat. Do not allow the render to bridge the DPC.

Leave a 25 mm gap at floor level to avoid capillary transfer of moisture from the floor into the wall structure.

Second Render Coat

The second coat should be applied once the first has sufficiently set, usually the following day under normal conditions. It must be applied to a thickness of 6 mm to 10 mm, ensuring the combined thickness of both coats is at least 16 mm.

The mix for this coat should be 4 parts washed sharp sand to 1 part Ordinary Portland Cement, with gauging water incorporating RenderMix at the same 1:40 dilution. Apply the coat evenly over the first, and scratch the surface again to prepare for the finishing coat.

The surface should be kept damp if conditions are hot or windy to avoid rapid drying and potential cracking.

Finishing

The finishing coat should be 1 mm to 3 mm thick and must be porous to allow moisture to escape during the drying out period. It should not be over-trowelled or polished.

For best results, apply Wykamol High Impact Plaster Finish as a breathable, lightweight topcoat. If another finishing system is desired, consult our Technical Department for compatibility advice.

Angle beads should not be fixed using gypsum-based adhesives, as this may compromise the system’s breathability.

Fix skirting boards using solvent-free adhesive, such as Soudal Grip All - Sovlent Free, and ensure all timber is treated with a dual-purpose fungicidal/insecticidal solution, such as WoodGuard Dual F/I. Allow preservatives to dry fully before fixing.

Re-Decoration

Breathable matt emulsion paints may be applied after 3 to 4 weeks, depending on ambient conditions and wall drying. Non-breathable paints or wall coverings must not be applied for at least 6 months to allow full moisture evaporation.

Always check the moisture content of the wall before applying any impermeable finishes, as premature sealing may lead to trapped moisture and future failure of the surface.

Cleaning

All tools, mixing equipment and trowels should be cleaned thoroughly with clean water immediately after use. Hardened material can only be removed mechanically. Clean up any spills promptly to avoid staining or contamination.

Other Information

RenderMix complies with BS EN 934-3 and forms part of the Sovereign Replastering Specification. When used correctly in conjunction with a chemical DPC system, it will prevent the migration of hygroscopic salts to the finished surface while allowing the wall to breathe and dry out naturally.

RenderMix is not designed to act as a vapour barrier and should not be used in systems requiring complete moisture containment. Always store RenderMix upright in its original container, in dry, frost-free conditions, and away from direct sunlight. Shake before each use to ensure even consistency and performance.

Q) What is Sovereign RenderMix and what is it used for?

A) Sovereign RenderMix is a high-performance liquid additive formulated to enhance the performance of sand and cement backing coats used after the installation of a chemical damp proof course (DPC). It functions both as a waterproofer and salt-retarding agent, making it particularly suitable for use in re-rendering systems where rising damp has previously occurred. By improving the workability of the mix and providing moisture resistance, Sovereign RenderMix ensures a consistent and durable render that protects interior finishes from the damaging effects of residual hygroscopic salts and moisture ingress. It forms part of the Sovereign re-rendering specification and is fully compliant with BS EN 934-3, the recognised standard for masonry admixtures.

Q) How does Sovereign RenderMix prevent salt migration to surface finishes?

A) One of the primary roles of Sovereign RenderMix is to stop hygroscopic salts from migrating through the render layer to the final decorative surface. After rising damp has affected a wall, salts can remain in the masonry and migrate towards the surface through capillary action. When these salts reach the final plaster or paint layer, they can cause staining, bubbling, and eventual breakdown of the finish. RenderMix forms a salt-retarding barrier within the render, binding these contaminants within the backing coats and stopping them from causing visible or structural damage. This makes the product vital in the prevention of long-term post-DPC decorative failure.

Q) Is Sovereign RenderMix breathable?

A) Yes, Sovereign RenderMix is designed to be vapour permeable, allowing moisture within the treated masonry to gradually escape through evaporation. Unlike some waterproofing additives that trap moisture behind a sealed layer, RenderMix maintains breathability, supporting the drying process essential after the installation of a chemical DPC. This property makes it ideal for use in older buildings, heritage projects, and remedial damp proofing systems where breathability and moisture management are key to long-term success.

Q) Can Sovereign RenderMix be used in general rendering work?

A) While Sovereign RenderMix is specifically formulated for use in backing renders following the insertion of a chemical DPC, it can be used in other remedial or specialist situations where salt resistance and breathability are required. However, it is not designed for structural concrete or floor screeds, nor should it be used in decorative topcoats or areas subjected to continuous water pressure. Its intended purpose is to form part of a post-damp proofing re-rendering system in walls affected by rising damp.

Q) How should Sovereign RenderMix be incorporated into a render mix?

A) Sovereign RenderMix should be thoroughly shaken before use and diluted directly into the gauging water before being added to the dry sand and cement mix. For each 25 kg of cement, 175 ml of RenderMix should be used, ensuring the dilution is well mixed. It is important to use CEM I Ordinary Portland Cement and washed sharp sand, and to avoid using any other admixtures or blended cements. The resulting render mix will be easier to apply and more resistant to salt and moisture penetration.

Q) What render mix ratios should be used with Sovereign RenderMix?

A) For the first coat of render, use a mix of 3 parts washed sharp sand to 1 part Ordinary Portland Cement, incorporating the diluted RenderMix into the gauging water. The thickness should be between 8 mm and 12 mm. The second coat should follow with a mix of 4 parts sand to 1 part cement, applied at a thickness of 6 mm to 10 mm. Both coats must incorporate RenderMix to ensure consistent water resistance and salt control throughout the render system.

Q) Can Sovereign RenderMix be used with lime-based renders?

A) No, Sovereign RenderMix is not suitable for use in lime-based mortars or gypsum-based plasters. It is designed specifically for use with sand and cement renders following damp proofing work. The inclusion of RenderMix in lime mortars may interfere with carbonation and breathability, and it is not compatible with the chemical makeup of lime binders. For breathable lime-based systems, alternative products should be considered.

Q) What are the benefits of using Sovereign RenderMix after DPC installation?

A) Sovereign RenderMix offers multiple benefits in walls that have undergone damp proofing, including improved workability of the render mix, reduced water absorption, resistance to salt migration, and vapour permeability. By incorporating RenderMix, contractors ensure that the render not only protects against further moisture damage but also supports the drying out of the wall. It also prevents long-term decorative failure by keeping salts within the backing coat rather than allowing them to affect the surface.

Q) How does Sovereign RenderMix improve workability of render?

A) Sovereign RenderMix contains carefully balanced ingredients that enhance the cohesion and plasticity of the render mix. This makes the render easier to trowel, smoother to apply, and more consistent in finish without the need for separate plasticisers. The improved workability also reduces the risk of cracking and separation during application, particularly in challenging site conditions where varying temperature or humidity can affect mix performance.

Q) What substrates is Sovereign RenderMix suitable for?

A) Sovereign RenderMix is suitable for use on most masonry substrates including brickwork, blockwork and stone, provided they are stable and capable of supporting the render system. It is specifically formulated for use on internal walls affected by rising damp. It is not intended for structural concrete, gypsum-based surfaces, or for use in floor screeds or heavily water-exposed areas such as retaining walls unless other waterproofing measures are in place.

Q) Is a specific type of cement required when using Sovereign RenderMix?

A) Yes, only CEM I Ordinary Portland Cement should be used in mixes containing Sovereign RenderMix. Blended cements such as CEM II, CEM III or masonry cements, as well as high alumina cements, must not be used, as they can negatively affect the chemical interaction between the render and the additive, reducing the product’s performance and compatibility with the overall damp proofing system.

Q) Can Sovereign RenderMix be used in heritage buildings?

A) Sovereign RenderMix is well suited for heritage and conservation work, particularly in properties where rising damp has been treated and re-rendering is necessary. Its breathable formulation allows the building fabric to dry naturally, which is essential in older buildings constructed with traditional materials. It provides the needed protection against salt and moisture without trapping water inside thick masonry walls, which is a common concern in conservation projects.

Q) Can Sovereign RenderMix be used as a waterproofing system by itself?

A) No, Sovereign RenderMix is not a standalone waterproofing system. It is designed as part of a damp proofing re-rendering specification and must be used in conjunction with a chemical damp proof course and the correct render coats. While it provides excellent water resistance within render layers, it does not prevent water ingress from external sources or rising damp if used on its own without a DPC system.

Q) What are the storage requirements for Sovereign RenderMix?

A) Sovereign RenderMix should be stored upright in its original container in a cool, dry, and frost-free environment. Storage temperatures should be between +5°C and +25°C, and the container should be kept sealed when not in use. Avoid prolonged exposure to direct sunlight or heat sources, which may degrade the product over time. Always shake the container before use to ensure consistency of the formulation.

Q) Can Sovereign RenderMix be used with coloured renders or finishes?

A) Sovereign RenderMix is added only to the backing coats, which are not visible once the final finish is applied. It is not typically used in coloured or decorative finishes, which should be breathable and compatible with the system. For decorative topcoats, breathable materials such as Wykamol High Impact Plaster Finish or suitable lime-based finishes should be considered. Always consult the manufacturer for compatibility if a coloured finish is required.

Q) What thickness of render is recommended when using Sovereign RenderMix?

A) When applying render with Sovereign RenderMix, the first coat should be between 8 mm and 12 mm thick, and the second coat between 6 mm and 10 mm, for a combined minimum of 16 mm. The finishing coat, which should be breathable and porous, is applied at 1 mm to 3 mm. This build-up ensures durability, salt protection and sufficient mass to resist moisture while remaining breathable.

Q) How long should you wait before decorating over render containing Sovereign RenderMix?

A) Decorative finishes should not be applied until the wall has fully dried out. In normal conditions, breathable matt emulsion paints may be applied after approximately 3 to 4 weeks. However, non-breathable paints or wall coverings must not be used for at least 6 months, or until the wall is dry enough to prevent trapped moisture. Premature application of impermeable coatings may lead to bubbling, blistering and eventual failure of the finish.

Q) Can Sovereign RenderMix be used in external rendering?

A) Sovereign RenderMix is designed specifically for internal render backing coats applied after damp proofing. It is not intended for external rendering or surfaces exposed to weathering and driving rain. For exterior applications, other specialised additives and renders should be considered that are formulated for freeze-thaw resistance and UV durability.

Q) What is the coverage rate of Sovereign RenderMix?

A) Each litre of Sovereign RenderMix will treat approximately 5.7 mixes when used at 175 ml per 25 kg of cement. For typical internal wall areas, this equates to a high coverage rate, and the 5-litre container provides ample additive for use across multiple rooms or a full re-rendering project, depending on the wall height and thickness of the render.

Q) Is Sovereign RenderMix approved to any British Standards?

A) Yes, Sovereign RenderMix is manufactured in compliance with BS EN 934-3, which sets out requirements for masonry and plaster admixtures. This ensures it meets established criteria for quality, safety, and performance in construction applications, making it a trusted component within Sovereign’s damp proofing and re-rendering systems.

Technical Data Sheet

Safety Data Sheet