Fosroc Renderoc Plug 1
Single-component, chloride-free rapid-setting mortar that plugs running water and active leaks in roughly one minute – for concrete, masonry, tunnels and below-ground structures.
What is it?
A single-component, cement-based rapid-setting mortar that hardens in about one minute to stop running water and active leaks. It conforms to BS EN 1504 Class R1.
Where is it used?
Basements, lift pits, water tanks, tunnel and segment linings, sewage systems, manholes, foundations and any structure where water is actively seeping or gushing through cracks, joints or holes.
Why use it?
It seals live leaks instantly without dewatering, develops strength fast, bonds tightly to the substrate, has low exotherm to avoid thermal cracking and is chloride-free so it will not corrode embedded steel.
How is it applied?
Mixed roughly 1 part clean water to 3 parts powder by volume to a stiff dough, then hand-pressed (gloved) firmly into the leaking point and held until it sets and the flow stops.
About Fosroc Renderoc Plug 1
Fosroc Renderoc Plug 1 is a factory blended, single-component, cement-based mortar engineered for one job that most products cannot do well: stopping water that is already flowing. When a basement wall weeps, a construction joint in a water tank starts to drip, or water gushes through a tie-bolt hole in a diaphragm wall, conventional repair mortars wash out before they can set. Renderoc Plug 1 is designed around a flash set, reaching initial set in approximately one minute at 20 degrees C, which lets it grip and seal against active hydrostatic pressure.
The product belongs to Fosroc’s Renderoc concrete-repair family but is positioned as a specialist water-stopping plug rather than a general patching mortar. The number 1 in the name denotes its ultra-rapid one-minute set; its sister product Renderoc Plug 20 sets in around twenty minutes and is used where a slightly longer working time is acceptable and, in the case of the Plug 20 grade, where potable-water contact approval is required. Renderoc Plug 1 is supplied ready-blended in moisture-resistant bags, eliminating the site batching errors that plague hand-mixed sand-cement plugs.
In the Indian context, where waterproofing failures in basements, sumps, sewage treatment plants and metro tunnels are a recurring and expensive problem during and after the monsoon, a reliable instant plug is a frontline emergency material. Space Arc Engineering supplies Renderoc Plug 1 to contractors, waterproofing applicators and facility maintenance teams across Delhi NCR and Pan-India as part of a complete leak-sealing system. It is important to understand the product honestly: Renderoc Plug 1 is a leak-arresting plug, not a standalone waterproofing membrane. It stops the immediate ingress so that a durable repair, crystalline coating or injection system can then be applied to the now-dry surface.
The technical insight
The performance of Renderoc Plug 1 comes from a blend of high-alumina or rapid-hydrating cement chemistry with selected fillers and accelerating additives, producing a flash set that overcomes hydrostatic flow. As the mortar hydrates it expands very slightly, wedging itself into the cavity and forming a mechanical and chemical bond against the water pressure rather than being pushed out. The formulation is deliberately low-exotherm so that the rapid reaction does not generate enough heat to cause thermal micro-cracking, a real risk with fast-setting cements. It is also chloride-free, which matters in reinforced concrete because chloride-accelerated set products would risk pitting corrosion of the rebar over time. Early strength gain is high, with compressive strength of the order of 10 MPa within the first hour and day and rising to roughly 23 MPa at 28 days, enough to hold the plug permanently in place while remaining compatible with the surrounding concrete. Because the set is so fast, the material must be mixed in small batches and worked immediately; once it begins to stiffen in the hand it cannot be re-tempered.
Where it is used
- Plugging live water leaks through cracks, holes and construction joints in basement and retaining walls
- Sealing water ingress at tie-bolt holes and snap-tie pockets in diaphragm walls and shear walls
- Emergency stopping of running water in tunnels, shaft linings and pre-cast segment joints
- Arresting leaks in water-retaining structures such as tanks, sumps, lift pits and reservoirs
- Sealing seepage in sewage systems, manholes, drainage chambers and below-ground access pits
- Plugging water entry in foundations, basements and mines before applying permanent waterproofing
- Anchoring and rapid fixing where a fast initial set is required against damp or wet substrates
Key advantages
- Stops running water and active leaks in approximately one minute without needing to dewater first
- Single-component, pre-bagged material – only clean water is added on site, removing batching errors
- Excellent bond to damp and wet concrete and masonry substrates
- Chloride-free, so it is safe to use against embedded reinforcement steel
- Low exotherm minimises the thermal cracking risk associated with rapid-set cements
- High early strength, gaining usable load capacity within the first hour
- Conforms to BS EN 1504 Class R1, giving a recognised repair-mortar classification
- Works on horizontal, vertical and overhead surfaces
Limitations & considerations
- It is a leak plug, not a waterproofing membrane – a permanent waterproofing system is still required afterwards
- Very short working time (about one minute) means only small batches can be mixed and it must be applied immediately
- Minimum applied thickness is around 15 mm; it is not suited to thin feather-edged repairs
- Not a structural repair or large-volume reinstatement mortar – use a Renderoc repair mortar for that
- Renderoc Plug 1 is not the grade approved for potable / public water-supply contact – the Plug 20 grade carries that approval
- Six-month shelf life and sensitivity to moisture demand careful dry storage in Indian humidity
- High exotherm-free but rapid reaction means large masses or hot-weather use need extra care and small batches
Selection & best practice
Cut out and clean the leaking area to firm, sound substrate and, where flow allows, form a small undercut or dovetail so the plug locks in mechanically. Wear waterproof gloves and mix only as much as can be applied in seconds – roughly 1 part clean water to 3 parts powder by volume to a stiff, dough-like consistency. Squeeze the mortar in your gloved hand until it begins to warm and stiffen, then press it firmly into the leak point and hold it under hand pressure for a minute or more until the set is achieved and the water flow stops. Work from the edges of a leaking zone towards the strongest jet last. Apply in a minimum thickness of about 15 mm. Once leaks are arrested and the surface is dry, overcoat with a permanent system such as a Fosroc crystalline or cementitious waterproof coating, or a Renderoc repair mortar, to deliver lasting durability. In hot Indian conditions use cool clean water, keep batches very small, and store unopened bags in a dry, covered area off the floor.
Specifications
| Product type | Single-component cementitious rapid-setting water-stopping mortar |
| Initial set time | Approx. 1 minute at 20 degrees C |
| Standard / classification | Conforms to BS EN 1504, Class R1 |
| Mixing ratio | Approx. 1 part clean water to 3 parts powder, by volume |
| Mixed consistency | Stiff / dough-like, hand or trowel applied |
| Minimum applied thickness | 15 mm |
| Compressive strength (1 hour / 1 day) | ~10 MPa |
| Compressive strength (28 days) | ~23 MPa |
| Chloride content | Chloride-free |
| Exotherm | Low (minimises thermal cracking) |
| Packaging | 6 kg bags (yielding approx. 3 litres of mortar) |
| Shelf life | 6 months in unopened bags, stored dry |
| Surfaces | Horizontal, vertical and overhead |
Industry use cases
Basement & below-ground waterproofing
Sealing live leaks at construction joints, tie-bolt holes and cracks in basement and retaining walls before a permanent membrane or crystalline coating is applied.
Metro & tunnelling
Emergency plugging of water ingress at pre-cast segment joints, shaft linings and grout-hole leaks in metro and infrastructure tunnels.
Water & wastewater (STP / WTP)
Arresting seepage in sewage treatment tanks, sumps, manholes and drainage chambers; for potable-water contact the Renderoc Plug 20 grade is specified instead.
Building maintenance & facilities
Rapid response to leaking lift pits, water tanks, terrace junctions and plumbing penetrations in commercial and residential buildings across Delhi NCR.
Industrial & mining
Plugging water entry in foundations, pits and mine workings where flow must be stopped instantly to allow work to continue.
Frequently asked questions
How fast does Renderoc Plug 1 actually set?
Can Renderoc Plug 1 stop water that is already flowing?
Is Renderoc Plug 1 a complete waterproofing solution on its own?
What is the difference between Renderoc Plug 1 and Renderoc Plug 20?
Is it safe to use on reinforced concrete?
How do I mix and store it correctly in Indian conditions?
How we position Fosroc Renderoc Plug 1
Renderoc Plug 1 is the go-to instant plug within the Fosroc system and is best understood as the first step in a leak-repair sequence rather than the finished waterproofing. Pair it with permanent Fosroc systems – a Renderoc repair mortar to rebuild profile, or a Fosroc crystalline / cementitious coating to waterproof the dried surface – and use Renderoc Plug 20 where a longer set or potable-water approval is needed. In the Indian market it competes directly with other rapid water-stopping plugs: Sika’s Sika-4a / SikaPlug, Dr. Fixit Pidiproof LW+ companion plug products and the Dr. Fixit Roofseal range, MYK / MBS water-plug mortars, and STP (Bautech) plugging compounds. All are quick-set hydraulic plugs aimed at the same problem; the practical choice usually comes down to availability, set-time grade and the wider repair system being specified. Space Arc Engineering, as an authorised Fosroc distributor, supplies Renderoc Plug 1 with technical guidance so the right grade and the right follow-up system are specified together.
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Authorised distribution, technical advice & professional application across Delhi NCR and Pan-India.