About MC-Bauchemie Oxal SPM

Delhi NCR has plenty of older masonry — colonial and mid-century bungalows, boundary walls, semi-basements — built without a damp-proof course worth the name, or where the original DPC has long since failed. Add monsoon capillary rise and years of efflorescence, and the pattern repeats on site after site: crumbling plaster, white salt bloom, brickwork that’s structurally fine but chemically exhausted at the surface. Patch it with ordinary cement-sand render and the same salts attack the repair within a season, because standard OPC mortar contains tricalcium aluminate, which reacts with sulphates and expands, cracking the new render from the inside out.

Oxal SPM is MC-Bauchemie’s answer to that specific failure mode — a one-component, factory-dosed mortar built on a tricalcium-aluminate-free binder with low active alkali content, so the chemistry that destroys renders on salt-loaded walls simply isn’t present to react. On site it behaves like an ordinary trowel mortar: mix with water, apply in layers, float to finish. But it does two jobs in one pass — it levels and rebuilds the damaged substrate, and once cured it’s impermeable to water under both positive and negative pressure, holding back moisture whether it’s pushing in from outside a basement wall or wicking up from below. For interior waterproofing build-ups, MC-Bauchemie pairs it with Oxal DS-HS as a follow-on coat; used alone, it’s simply a durable, chemically stable render for masonry that keeps failing for reasons no amount of ordinary plaster will fix.

The technical insight

The defining fact on MC-Bauchemie’s own data sheet is the binder description: “tricalcium aluminate-free binder, low active alkali content.” Tricalcium aluminate (C3A) is the Portland cement clinker phase that reacts with sulphate ions to form ettringite, a mineral that expands as it crystallises — this is the mechanism behind sulphate attack, and exactly why ordinary cement plaster on salt-contaminated brickwork blisters, cracks and delaminates. Removing C3A removes the reaction pathway itself, not just the symptom; low active alkali content limits the alkali-salt interactions that drive efflorescence in the same way. Also worth noting: the data sheet’s 3-hour water-resistance window at +23°C means the mortar hardens fast enough to cope with early moisture exposure on a genuinely damp job site — the normal condition on a rising-damp repair, not the exception. All published figures are MC-Bauchemie’s own lab values at +23°C and 50% relative humidity; the sheet doesn’t cite a specific IS/ASTM/BS/EN standard, so treat the numbers as manufacturer-verified performance data rather than third-party-certified figures when writing a heritage or institutional spec.

Where it is used

• Restoration render for salt- and damp-affected brick, block and stone masonry
• Levelling, defect repair and mortar-joint filling before replastering
• Forming coved skirtings at wall/floor junctions (min. 5 cm radius after notching)
• Waterproofing basement, retaining and boundary walls against positive and negative water pressure
• Sacrificial barrier coat ahead of interior waterproofing with Oxal DS-HS
• Rising-damp and efflorescence-affected plinth walls in older and heritage buildings
• Parapets, chajjas and water-tank masonry surrounds exposed to repeated wetting
• General interior/exterior restoration render on mineral masonry substrates

Key advantages

• One-component — just add water, no separate polymer liquid or two-part dosing to get wrong
• True two-way water resistance under both positive and negative pressure, unusual for a trowel-applied render
• Sulphate-resistant, low-alkali chemistry resists the reaction that destroys ordinary cement plaster on salty walls
• Hardens rapidly even on damp substrates, which is the realistic condition on most renovation sites
• Frost resistant, useful margin for Space Arc’s North India and hill-station project sites
• Repairs and waterproofs in one material and one pass, cutting coats and site time
• Forms covings directly without needing a separate fillet/coving compound
• Part of a documented MC-Bauchemie system with Oxal DS-HS rather than a standalone product

Limitations & considerations

• Rigid cementitious render, not crack-bridging — the underlying masonry needs to be structurally sound and stable
• 2 mm maximum grain size keeps it in render/mortar territory, not a structural repair mortar for load-bearing defects
• Performance depends on correct prep — joints raked back at least 1 cm and absorbent substrates pre-wetted — or the data sheet’s numbers won’t hold on site
• Finish is cement grey only; a decorative plaster or paint system is still needed over it on exposed surfaces
• Sold only in 25 kg bags, and the manufacturer’s data sheet cites no IS/ASTM/BS/EN standard, so figures should be read as MC-Bauchemie’s own lab data rather than third-party-certified values

Selection & best practice

Specifications

Industry use cases

How we position MC-Bauchemie Oxal SPM

Oxal SPM sits within MC-Bauchemie’s Oxal range for masonry restoration, and it’s designed to be read alongside Oxal DS-HS — the interior waterproofing coat MC-Bauchemie names as its companion product for full interior damp-proofing build-ups; Space Arc can supply and apply both together as a system rather than treating SPM as a standalone render. Buyers used to defaulting to Fosroc should note that Fosroc’s closest lines — the Renderoc repair-mortar range for concrete, and the Brushbond cementitious tanking-coat range — solve concrete repair and tanking respectively, but neither is built as a dedicated sulphate-resistant render for salt- and damp-affected masonry the way Oxal SPM is. For that specific failure mode, Oxal SPM stays a fairly narrow, purpose-built choice rather than one of several interchangeable options.

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