MC-Bauchemie Oxal NHL 3 historic
The cement-free NHL 3.5 lime render MC-Bauchemie built for buildings that predate cement itself.
What is it?
A factory-batched, absolutely cement-free render based on NHL 3.5 (natural hydraulic, Roman-lime-based) lime, formulated by MC-Bauchemie specifically as a breathable levelling and finishing coat for heritage masonry.
Where is it used?
Havelis, forts, temples, colonial-era bungalows, churches, ASI-protected monuments and any listed or conservation-committee-supervised building where the specification excludes OPC-based plaster.
Why use it?
Its low binder strength and high vapour permeability let old lime-mortar brick and stone walls breathe and move the way they were built to, instead of trapping moisture and pushing salts to crystallise behind a rigid cement skin.
How is it applied?
Hand- or machine-applied as a spatter coat, then a combed levelling coat of at least 15 mm cured one day per millimetre before further layers, finished with a further coat and floated smooth — never sealed under a film-forming paint.
About MC-Bauchemie Oxal NHL 3 historic
Oxal NHL 3 historic is MC-Bauchemie’s answer to a problem every conservation architect in India runs into: ordinary cement-sand plaster is chemically wrong for old lime-built masonry. Havelis in Rajasthan, colonial bungalows in Lutyens’ Delhi, temples, forts and ASI-protected monuments were built with lime mortars that breathe and move — render them in OPC and you trap moisture, push salts to crystallise behind a rigid skin, and eventually spall the original brick or stone face away. Oxal NHL 3 historic sidesteps that entirely: it’s an absolutely cement-free render built on NHL 3.5 natural hydraulic lime, a Roman-lime-based binder MC-Bauchemie formulates specifically for restoration work rather than adapting a general-purpose plaster. It sits within the company’s wider Altbau und Mauerwerk (old-building and masonry) system, and is supplied in India through Space Arc Engineering as an authorised MC-Bauchemie distributor and applicator for Delhi NCR and pan-India heritage projects.
On the wall, it behaves like the traditional lime renders it’s meant to replace or repair — applied as a spatter coat, then a combed levelling coat of at least 15 mm, cured for a full day per millimetre before the next layer goes on, and finished with a further coat before floating. That staged build-up, combined with a deliberately low binder strength and high vapour permeability, keeps shrinkage cracking down and lets residual dampness and salts migrate outward through the render rather than getting trapped behind it. It suits interior and exterior walls and ceilings on brick, stone or existing lime-mortar masonry, and it’s machine-applicable with standard plastering pumps, so contractors aren’t limited to slow hand-application on larger heritage facades. Space Arc supplies it alongside technical guidance on substrate prep, layering schedules and compatible finish coats — guidance that matters more here than on almost any standard plaster, because a heritage lime render forgives far less improvisation.
The technical insight
NHL 3.5 is a defined class under EN 459-1, the European standard for building limes — it identifies a natural hydraulic lime (burnt from a naturally impure limestone, not gauged with added cement or pozzolan) with a 28-day compressive-strength band of roughly 3.5–10 N/mm², well below any OPC-based render. That deliberate weakness is the point on heritage masonry: the render stays the sacrificial, more flexible layer, so movement and salt crystallisation happen in the plaster rather than in centuries-old brick or stone. Oxal NHL 3 historic’s own tested flexural strength (≥0.3 N/mm²) and fine 2.2 mm maximum grain size back this up — it’s formulated to go on in a thin, workable coat that still resists cracking, rather than behaving like a coarse structural render. That combination of low binder strength and high vapour openness is what conservation architects mean when they specifically ask for “NHL,” not just generic lime plaster.
Where it is used
- Heritage and conservation renders on brick, stone (sandstone/laterite) and lime-mortar masonry under ASI or state heritage-committee supervision
- Finishing/levelling coat over rising-damp-treated walls, typically paired with a horizontal damp-proof barrier system
- Interior and exterior wall and ceiling renders in havelis, forts, temples, churches and colonial-era bungalows
- Salt-affected masonry where a breathable, non-cementitious render is specified to avoid trapping moisture behind the surface
- Restoration of listed Grade I and II heritage buildings for museums, state heritage departments and private heritage-hotel owners
- New lime-mortar masonry where the architect specifies traditional materials for authenticity rather than cost
- Base substrate ahead of a limewash or breathable mineral-paint finish (SD ≤ 0.2 m)
- Plain render base coat prior to specialist sculptural or artificial-stone detailing on ornamental facades
Key advantages
- Absolutely cement-free, even below the declaration limit — meets conservation briefs that expressly disallow OPC near historic fabric
- NHL 3.5 Roman-lime-based chemistry gives genuine material compatibility with lime-built historic masonry, not just a modern render dressed up as heritage-friendly
- High water-vapour permeability lets residual damp evaporate outward instead of being trapped behind the render
- Low shrinkage and cracking tendency compared with straight cement or poorly gauged lime renders
- Machine-sprayable with standard plastering pumps and open spiral pump systems, speeding up work on large heritage facades
- Felted or floated finish gives an authentic traditional lime-render surface texture rather than a machine-smooth modern look
- 12-month shelf life in original unopened bags, which eases logistics for remote heritage sites with long lead times
- Sits within a documented MC-Bauchemie restoration system, so it can be specified alongside compatible damp-proofing and salt-transport products rather than as a standalone material
Limitations & considerations
- Slow, staged application — one day of curing per millimetre of layer thickness — makes it far slower than a standard cement or gypsum plaster programme
- Partially set mortar cannot be re-tempered with extra water or fresh material, so batch sizes need tight planning against crew output
- Strict working-temperature window (substrate ≥5°C, ambient ≥10°C) rules out early-morning winter application in North Indian hill and plains sites alike
- Needs a genuinely experienced lime-plastering crew — mishandled curing in sun or wind causes exactly the cracking the product is meant to prevent
- Only water-vapour-open, non-film-forming finishes (SD ≤ 0.2 m) can go over it afterward, so ordinary plastic emulsion paint is not an option later
- Priced and specified as a heritage-conservation material, not a general repair plaster, so it needs a dedicated conservation budget line rather than a standard finishing allowance
Selection & best practice
Strip any old render back to sound masonry, rake out dust, salts and loose material, and pre-wet dry or highly absorbent brick and stone before starting. Batch-mix by weight — one 25 kg bag to 5–5.5 litres of clean water with a slow-speed paddle mixer until lump-free — and never re-temper a batch that has begun to set. Apply as a full-coverage spatter or dash coat first, then build the levelling coat to at least 15 mm with a feather-edge, comb it while green with a 6–8 mm toothed trowel, and hold back further layers for a full day per millimetre of thickness already applied; this staged curing is what actually controls shrinkage cracking. Finish with a further coat of at least 10 mm, float it with a non-absorbent board, and protect the curing render from direct sun, wind and rapid drying for several days, exactly as you would a traditional lime plaster. Keep site temperatures within the stated window and finish only with SD ≤ 0.2 m breathable coatings — sealing it with ordinary paint defeats the purpose of specifying a lime render in the first place.
Specifications
| Binder system | NHL 3.5 natural hydraulic lime, absolutely cement-free |
| Maximum grain size | 2.2 mm |
| Mixing ratio | 25 kg powder : 5–5.5 L clean water |
| Working time | Approx. 30 minutes at 20°C / 65% RH (temperature-dependent) |
| Flexural strength | ≥ 0.3 N/mm² |
| Application temperature | Substrate ≥ 5°C; ambient ≥ 10°C |
| Colour | Natural white |
| Pack size | 25 kg bags; 40 bags (1,000 kg) per pallet |
| Shelf life | 12 months in original unopened packs, stored cool and dry |
Industry use cases
Heritage haveli and fort restoration (Rajasthan, Delhi NCR)
Levelling and finishing render on lime-mortar brick or sandstone walls where the conservation architect’s specification explicitly excludes OPC-based plaster.
Colonial-era bungalow and institutional building conservation
Re-rendering damp-damaged lime-plastered walls after rising-damp treatment, so the new coat stays chemically compatible with the original 19th- or early-20th-century lime construction.
Religious and monument structures (temples, churches, ASI buffer-zone buildings)
Breathable render for walls that must not be sealed with cement, keeping salt and moisture migration close to the building’s original behaviour.
Heritage hotel and adaptive-reuse projects
A felted or floated lime-render finish on repurposed heritage structures where authenticity of texture and material matters to the design brief.
Salt-affected masonry repair
Used as the main body render alongside a dedicated salt-transport plaster where efflorescence and rising damp have historically damaged the wall.
Frequently asked questions
Is Oxal NHL 3 historic the same as an ordinary lime plaster available locally?
Can it go directly onto old brick or stone, or does the wall need prep first?
How is this different from MC-Bauchemie’s other lime render, Oxal Kalkputz?
Will ASI or a state heritage committee accept this on a protected monument?
How soon can we paint or limewash over it, and with what?
What’s the pack size, and how do we plan quantities for a facade?
How we position MC-Bauchemie Oxal NHL 3 historic
Within MC-Bauchemie’s own Altbau und Mauerwerk (heritage and masonry restoration) range, Oxal NHL 3 historic is the core body and levelling render. It’s typically specified alongside Oxal HSL-W, an injected horizontal damp-proof barrier that stops rising damp before rendering begins; Exzellent STP historic, a salt-transport plaster for walls with severe efflorescence; Oxal Kalkputz, a lighter mineral lime-render alternative; and Elegant MRP, a finer natural-hydraulic-lime finishing coat that can go over the base render. Where the brief calls for sculptural or artificial-stone work rather than a flat render, MC-Bauchemie’s Oxal RM specialty spray mortar is the product to reach for instead. Outside the MC-Bauchemie stable, there is no genuine Fosroc equivalent to point specifiers toward — Fosroc’s masonry and repair range (Renderoc, Nitomortar, Conbextra) is built around modern polymer-modified and OPC-based chemistry for structural and industrial repair, not certified NHL 3.5 heritage lime. Projects working to a strict no-cement conservation brief generally stay within the MC-Bauchemie Oxal system end-to-end rather than mixing in a cement-based alternative.
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Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.