Fosroc Renderoc Plaster
A cement-based, polymer-modified ready-to-use plaster that needs only water on site — low permeability, non-shrink, and finished by trowel or spray for walls and ceilings.
What is it?
A factory-blended, cement-based polymer-modified dry-powder plaster that becomes a workable rendering/plastering mortar on site with only the addition of clean water.
Where is it used?
Internal and external walls, ceilings, columns and partitions over block, brick, stone masonry and concrete substrates.
Why use it?
It removes site batching of sand and cement, gives consistent quality bag-to-bag, lowers water permeability, resists shrinkage cracking and cuts rebound wastage.
How is it applied?
Mix one bag with the recommended water using a slow-speed drill, then apply by trowel or plastering spray machine in controlled thickness and cure as for cementitious mortar.
About Fosroc Renderoc Plaster
Fosroc Renderoc Plaster is part of the well-established Renderoc range of repair and rendering mortars and is positioned as a ready-to-use replacement for traditional site-mixed sand-cement plaster. It is supplied as a pre-blended dry powder of cement, graded fillers and chemical additives, including a polymer that improves adhesion, cohesion and water resistance. On site, the contractor adds only clean water to produce a consistent cementitious mortar, removing the variability that comes from manually proportioning sand, cement and water in the open.
In the Indian market the product is commonly encountered as Renderoc Ready Plaster, the India SKU of the same family, used for both external rendering and internal plastering on block masonry, brick and stone masonry, and concrete surfaces. Because every bag is factory-graded, the plaster behaves the same on the first wall and the hundredth, which is a meaningful advantage on large residential, commercial and institutional projects where labour quality and river-sand availability fluctuate.
The headline characteristics published by Fosroc are that it is a non-shrink, polymer-modified premixed plaster with low permeability to water and excellent thermal compatibility with the concrete or masonry it covers. It can be finished by hand troweling for smaller areas or pumped through a plastering spray machine for high-output sites, and it is available in a range of colours so that in many cases a separate decorative finish coat is not strictly necessary. For Space Arc Engineering customers across Delhi NCR and Pan-India, it sits in the toolkit alongside Fosroc’s dedicated structural repair mortars (Renderoc HB, Renderoc S, Renderoc GP) as the general-purpose rendering and plastering layer rather than a high-strength patch repair material.
The technical insight
The performance of Renderoc Plaster comes from polymer modification of an ordinary Portland cement matrix. The polymer (a redispersible powder blended into the dry mix) forms a flexible film as the mortar hydrates and dries, bridging micro-voids between cement grains and the substrate. This does three things that matter in practice. First, it raises bond strength to masonry and concrete, so the plaster keys to the wall instead of relying purely on a mechanical grip — which is why a spatterdash or key coat can often be reduced on dense substrates. Second, the film reduces interconnected capillary porosity, lowering water permeability and water absorption, so the rendered surface resists wind-driven rain and slows carbonation and chloride ingress into the structure behind it. Third, the graded filler skeleton plus the polymer’s water retention reduces plastic and drying shrinkage, the root cause of the hairline map-cracking that plagues thick site-mixed plaster. The mix is also designed to be non-sagging, meaning it holds its shape on vertical and overhead work at the recommended thickness without slumping — the property that lets it be applied to ceilings and at the upper end of its thickness band in a single pass. Thermal compatibility with concrete (a coefficient of thermal expansion close to that of the substrate) keeps the render and the structure moving together through Indian summer-to-monsoon temperature swings, avoiding the debonding seen when an incompatible skim is applied over concrete.
Where it is used
- External rendering of block, brick and stone masonry on residential and commercial buildings
- Internal plastering of walls, ceilings, columns and partitions in place of site-mixed sand-cement plaster
- Plastering of RCC concrete surfaces such as columns, beams and soffits where bond to dense substrate is needed
- Levelling and finishing coat over AAC / concrete block masonry that is prone to shrinkage cracking with conventional plaster
- High-output spray plastering on large projects (apartments, IT parks, institutional buildings) using a plastering machine
- Areas where low water permeability is desired, such as external facades exposed to driving rain
- Projects requiring consistent, quality-controlled plaster finish without dependence on river-sand quality
Key advantages
- Ready to use — only clean water is added on site, eliminating manual proportioning of sand and cement
- Consistent factory-graded quality from bag to bag, independent of local sand availability
- Polymer modification gives better adhesion to masonry and concrete substrates
- Low permeability to water and reduced water absorption, improving durability of the finish
- Non-shrink formulation that reduces shrinkage and map cracking compared to thick site-mixed plaster
- Non-sagging, so it can be applied at higher thickness and overhead (ceilings) in fewer passes
- Minimal rebound and wastage, lowering material loss especially during spray application
- Can be applied by trowel for small areas or by spray machine for high productivity
- Available in a range of colours, sometimes removing the need for a separate finish coat
- Excellent thermal compatibility with concrete, reducing debonding from temperature movement
Limitations & considerations
- It is a rendering/plastering plaster, not a structural repair mortar — for spalled, corroded-rebar concrete repair use Renderoc HB, Renderoc GP or Renderoc S instead
- Application thickness per coat is limited (the India variant is positioned for roughly 10–15 mm single-coat work); very thick build-ups need multiple coats or a separate levelling system
- As a cement-based product it requires proper curing; inadequate curing in hot, dry or windy conditions can still cause surface crazing
- It is not a waterproofing membrane — for tanking, terraces and wet areas use dedicated systems such as Brushbond, Nitoproof or Proofex
- Bond depends on correct surface preparation; loose, dusty, oily or unsound substrates must be cleaned and pre-wetted first
- Higher material cost per bag than raw sand and cement, offset by labour savings, lower wastage and consistency
- Mixed mortar has a limited working time and should be used before it stiffens; over-watering to restore workability weakens it
- Published Fosroc data for this product is largely descriptive; project-critical strength or coverage figures should be confirmed against the current regional TDS before specification
Selection & best practice
Treat Renderoc Plaster like a quality-controlled cement plaster, not a magic skim. Prepare the substrate first: remove dust, laitance, oil, mould-release agent and any loose material, and pre-wet the masonry or concrete to a saturated-surface-dry condition so the wall does not pull water out of the fresh mortar. On very dense or smooth concrete, use a Fosroc key coat / spatterdash to improve mechanical grip. Mix one full bag at a time with the manufacturer’s recommended quantity of clean water using a slow-speed drill and paddle until lump-free and consistent — never split bags by eye and never add extra water once it has stiffened, as this destroys strength and bond. Apply in even thickness within the recommended band; build up genuinely thick sections in more than one pass, allowing the first to take up. Rule and float to line, then cure the finished plaster by keeping it damp (fine spray or wet hessian) for at least the first few days, which is the single biggest factor in avoiding shrinkage cracks in Indian summer conditions. Always validate the current batch against the latest regional Technical Data Sheet from Fosroc before large-scale or specification use.
Specifications
| Product type | Cement-based, polymer-modified ready-to-use plaster (dry powder blend) |
| Composition | Blend of cement, graded fillers and chemical additives (incl. polymer) |
| Form / supply | Single-component dry powder; add clean water on site |
| Application method | Hand trowel or plastering spray machine |
| Substrates | Block / brick / stone masonry and concrete; walls, ceilings, columns, partitions |
| Application thickness (India variant) | Approx. 10–15 mm single-coat (confirm with current regional TDS) |
| Key characteristics | Non-shrink, non-sagging, low water permeability, reduced water absorption |
| Thermal compatibility | Compatible with concrete substrate (close coefficient of thermal expansion) |
| Colour | Available in a range of colours |
| Typical pack size (India) | 40 kg bag (distributor-listed; regional pack sizes vary) |
| Curing | Standard cementitious curing — keep damp after finishing |
Industry use cases
Residential & high-rise housing
Internal plastering and external rendering of block and brick masonry across apartment towers, where consistent finish and reduced shrinkage cracking cut snagging and repainting.
Commercial & IT parks
Machine-applied spray plastering of large wall areas for high daily output with low rebound wastage and predictable quality.
Institutional & public buildings
Plastering of columns, soffits and partitions in schools, hospitals and offices where labour quality varies and a controlled, low-permeability finish is wanted.
Facade & weather-exposed walls
External rendering on facades subject to driving monsoon rain, using the low water permeability to protect the masonry and structure behind.
AAC / concrete block construction
Finishing AAC and concrete block walls that crack easily under conventional thick plaster, benefiting from the non-shrink, polymer-modified formulation.
Frequently asked questions
Is Fosroc Renderoc Plaster a structural repair mortar?
What is the difference between Renderoc Plaster and Renderoc Ready Plaster?
Do I still need to add sand or cement on site?
Can it be applied by a plastering machine?
How thick can a single coat be?
Does Renderoc Plaster make the wall waterproof?
How we position Fosroc Renderoc Plaster
Within the Fosroc range, Renderoc Plaster (and its India SKU, Renderoc Ready Plaster) is the general-purpose rendering and plastering layer, distinct from the structural concrete-repair members of the Renderoc family — Renderoc HB (high-build vertical/overhead repair), Renderoc GP (general-purpose repair) and Renderoc S (sprayable repair) — which exist to reinstate damaged concrete and protect rebar. Choose Renderoc Plaster when the goal is a consistent, low-permeability finish coat over sound masonry or concrete; choose a Renderoc repair mortar when the concrete itself is spalled or the reinforcement is exposed. It is not a waterproofing product, so it is specified ahead of Fosroc membranes such as Brushbond and Proofex rather than instead of them. Against the wider market, it competes with ready-mix and polymer-modified plasters such as Sika’s plastering and rendering mortars, MYK Laticrete (MBS) wall putties and plasters, Dr. Fixit’s plaster and crack-resistant ranges, and STP (Pidilite/STP) rendering products; the practical decision usually turns on local distributor support, the published thickness and coverage for the exact regional SKU, and whether the project already standardises on the Fosroc system. As an authorised Fosroc distributor serving Delhi NCR and Pan-India, Space Arc Engineering can supply Renderoc Plaster alongside the correct primers, key coats and repair mortars and confirm the latest regional Technical Data Sheet before you specify.
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