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Interior waterproofing system

Water in your basement is not just a nuisance — it is structural damage in slow motion.

When excavation is not an option, an interior waterproofing system is the professional answer. MPM STARFLEX liquid membranes seal walls and floors from inside — even on wet or damp concrete — without disrupting the perimeter or halting operations.

Over 70 years of Italian chemical expertise. Certified durability up to 30 years.

 

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What is an interior waterproofing system — and when do you need one?

An interior waterproofing system is a solution applied from inside a building to stop water from penetrating through basement walls, floors, or underground structures. The membrane is applied to the internal face of the structure: no excavation, no disruption to the perimeter.

It is the right choice when:

  • the building is already standing and external excavation is prohibitively expensive or disruptive
  • the project is a renovation or retrofit of an existing basement
  • urban density, adjacent structures, or active infrastructure make exterior access impractical
  • speed of execution is critical and downtime must be minimised

 

Interior waterproofing does not replace exterior waterproofing where that is feasible. It is the professional’s answer when it is not.

Hydrostatic pressure: the main cause of basement water infiltration

Groundwater does not wait for cracks to appear — it creates them. As water accumulates around a foundation, it builds hydrostatic pressure that forces its way through any imperfection in concrete: a hairline crack, a construction joint, a pipe penetration. Over time, the result is water ingress, reinforcement corrosion, spalling, and mould.

A correctly specified interior waterproofing system is the first line of defence. The membrane must resist water pressure from the negative side — from within — which demands specific chemistry and adhesion performance that standard coatings do not provide.

Interior waterproofing products: the STARFLEX range

Not every waterproofing membrane performs from the inside. Interior applications present conditions that external systems are not designed for: water pressure acting in reverse, limited airflow during curing, substrates that are rarely dry. Every product in the STARFLEX range addresses these constraints directly.

Starflex HYBRID

Liquid membrane for wet basement walls

STARFLEX HYBRID

When the substrate is wet and there is no time to wait, STARFLEX HYBRID is the answer. This single-component aliphatic polymeric membrane bonds directly on wet or damp concrete in some cases also without a primer. Rapid cure even at low temperatures, outstanding elasticity and adhesion — the complete package for interior retrofit projects where site conditions are never ideal.

Starflex H-ZERO

Polyurethane waterproofing membrane for interior use

STARFLEX H ZERO

STARFLEX ONE is a single-component elastic bituminous water-based membrane built for high adhesion even on wet or irregular concrete. UV-resistant, extremely flexible, easy to apply — a practical, cost-effective solution for basement maintenance and restoration projects

Starflex C

Cementitious waterproofing for basement walls and pools

starflex c

When a mineral-based interior waterproofing system is preferred — for compatibility, regulatory, or substrate reasons — STARFLEX C delivers. This bi-component elastic cementitious mortar cures on damp or cold surfaces, bridges cracks, and bonds firmly to concrete and masonry. Ideal for swimming pools, water tanks, and basement walls with constant water exposure.

Starflex ULTRA (FR)

Polyurea waterproofing system for underground structures

starflex ultra

Certified durability up to 30 years. Wet-on-wet application. Rain-safe after 1 hour. Fire-certified B-roof T4. STARFLEX ULTRA is the benchmark product for underground structures and foundations that demand maximum long-term reliability — the interior waterproofing system where failure is not an option.

Starflex ONE

Waterproof coating for basement concrete repair and maintenance

STARFLEX-ONE

STARFLEX ONE is a single-component elastic bituminous water-based membrane built for high adhesion even on wet or irregular concrete. UV-resistant, extremely flexible, easy to apply — a practical, cost-effective solution for basement maintenance and restoration projects.

Product Applies on wet substrate? Key advantage Best for
STARFLEX HYBRID Yes — even with no primer Bonds on wet concrete, rapid cure Retrofit, difficult site conditions
STARFLEX ONE Yes if humid Easy application, UV-resistant Maintenance and restoration
STARFLEX C Yes — cures on damp surfaces Cementitious, crack-bridging Pools, tanks, masonry basements
STARFLEX H-ZERO Yes High elasticity, multi-substrate Moving structures, confined spaces
STARFLEX ULTRA (FR) No 30-year certified durability Critical underground structures
→ Request the full STARFLEX product brochure

Why contractors and engineers choose MPM for interior waterproofing

 

It bonds on wet concrete — where most products fail

Interior waterproofing often means working in a damp, poorly ventilated basement — exactly the conditions that compromise standard coatings. STARFLEX HYBRID and STARFLEX ONE are specifically formulated to maintain full adhesion and performance on wet substrates.

Seamless liquid membrane: no joints, no weak points

A liquid-applied interior waterproofing membrane conforms to every surface it touches: corners, pipe penetrations, irregular walls, construction joints. There are no laps, no overlaps, no seams where water finds a path through.

Certified performance: up to 30 years of documented durability

Certified durability up to 30 years. Independent testing to ETAG 005, CE 1504, CAM, BBA, and Broof T4. More than 100 international certifications across the STARFLEX range. When an engineer or building inspector asks for proof, MPM provides documentation — not reassurances.

Made in Italy — 70 years of applied chemistry, training and support included

MPM has been developing protective chemistry for construction since the 1950s. Five R&D laboratories, over 40 certified products, production capacity exceeding 50,000 kg per day. Every STARFLEX membrane is manufactured in Italy — and the expertise comes with the product: training programmes, site visits, specification guidelines, and ongoing support from the technical team that knows these systems from the inside out.

→ Become a STARFLEX distributor: talk to our tech team

Interior waterproofing system: application fields

Any below-grade or internal surface exposed to water pressure, ground moisture, or sustained humidity is a candidate for STARFLEX interior waterproofing. These are the most common applications.

Waterproofing an existing basement from inside

The most frequent application. Excavating around a standing building to waterproof from outside is expensive, disruptive, and often impossible in urban environments. Applying a STARFLEX system from inside stops infiltration without touching the perimeter — restoring the usability of the space with minimal disruption to the building or its occupants.

Foundation and retaining wall waterproofing — interior application

Foundations face constant attack from ground moisture and hydrostatic pressure. Where the external face is inaccessible, an interior waterproofing membrane applied to the internal surface stops the ingress pathway — preventing reinforcement corrosion and the slow-motion structural damage that follows unchecked infiltration.

Underground car park and trafficked slab waterproofing

Below-grade parking structures face water infiltration, chloride ingress from de-icing salts, and heavy mechanical load. STARFLEX HR-M — a self-levelling bi-component polyurea membrane with pedestrian and vehicle load resistance — provides combined structural and waterproofing protection for these demanding environments.

Swimming pools, water tanks, and water retention structures

Constant water contact, chemical exposure, and the need for a permanently watertight finish make interior waterproofing essential for pools, water tanks, and treatment basins. STARFLEX C deliver the chemical resistance and permanent adhesion these applications demand.

Tunnels, underpasses, and underground infrastructure

Structural movement, constant humidity, and sustained hydrostatic pressure define tunnel environments. MPM’s liquid membranes adapt to complex geometries without joints, providing long-term protection for infrastructure assets where maintenance access is infrequent and failure is costly.

Industrial facilities: pits, tanks, and buried structures

Underground service pits, inspection channels, buried process tanks, and technical basements in industrial plants need protection against both water and chemical aggression. STARFLEX products are selected according to the chemical agents present — delivering combined waterproofing and chemical resistance in a single system.

→ Talk to our technical team

Common questions about interior waterproofing

Can I apply an interior waterproofing system to an already-wet basement?

Yes. STARFLEX HYBRID and STARFLEX ONE bond directly on damp or wet substrates — the condition found in most retrofit projects. Active leaks should be stopped with injection mortar before membrane application, but the presence of surface moisture alone does not prevent application.

How long does an interior waterproofing system last?

STARFLEX ULTRA FR carries certified durability of up to 30 years. All products in the range are designed for long-term performance, combining high elasticity, crack-bridging, and resistance to sustained water pressure. Actual service life depends on correct application and substrate condition.

Does interior waterproofing work against hydrostatic pressure?

Yes. STARFLEX polymer and cementitious systems both resist sustained negative-side water pressure. Product selection and application thickness are matched to the pressure level expected for each project. 

Do I need a professional applicator for STARFLEX systems?

For guaranteed performance and warranty coverage, yes. MPM trains and certifies applicators and supports projects from specification to completion. Using a trained applicator is the difference between a system that lasts 30 years and one that fails in 3.

Stop water infiltration before it becomes structural damage

Water damage does not announce itself. An interior waterproofing system applied now costs a fraction of structural repair later.

MPM’s technical team will assess your project, identify the right STARFLEX system, and support the entire process — from specification through to completed application.

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