IDROSTOP B25 N

Mapei Idrostop Waterbar – Hydrophilic Expanding Waterstop for Concrete Construction Joints

Mapei Idrostop is a pre-formed, flexible hydrophilic rubber profile designed to create watertight construction joints in concrete structures. Manufactured with an acrylic polymer base, it gradually expands when in permanent contact with water, forming an active barrier that helps prevent water passing through construction joints.

Unlike bentonite-based waterstops, Idrostop contains no bentonite. Its composition is designed to maintain its properties through repeated expansion and contraction cycles and in contact with aggressive water, including seawater and water found in sewage treatment plants and sewers.

Key Benefits

• Hydrophilic expansion: Gradually expands in permanent contact with water to create an active waterproofing barrier.
• Up to 5 atm water resistance: Mapei states impermeability up to 5 atm under its test conditions.
• Bentonite-free: Acrylic polymer-based formulation without bentonite.
• Positive and negative water pressure: Expanding profile creates a barrier against water pressure.
• Flexible pre-formed strip: Suitable for different concrete joint configurations.
• Resistance to aggressive water: Maintains its properties in contact with seawater and water in sewage treatment plants and sewers.
• Multiple installation options: Can be fixed using Idrostop Mastic or suitable mechanical fixings.

Applications

Idrostop is designed to create watertight construction joints in civil, industrial and hydraulic structures, including:

• Joints between concrete floor slabs and vertical walls.
• Construction joints in foundations and retaining walls.
• Contact joints between different materials, including PVC or steel pipes passing through concrete.
• Swimming pools and sewage treatment tanks.
• Reservoirs, cisterns and hydraulic structures.
• Construction joints in tunnels and dams.
• Drinking-water reservoirs.
• Joints where conventional waterstops are difficult to install because of dense reinforcement.

Available Sizes and Packaging

Mapei Idrostop is available in the following sizes:

• Idrostop 10: 20 x 10mm – 6 rolls of 10 metres (60 metres total per box).
• Idrostop 15: 20 x 15mm – 6 rolls of 7 metres (42 metres total per box).
• Idrostop 25: 20 x 25mm – 6 rolls of 5 metres (30 metres total per box).

Technical Information

• Manufacturer: Mapei.
• Product: Idrostop.
• Product type: Hydrophilic expanding rubber waterstop.
• Form: Pre-formed flexible profile.
• Base material: Acrylic polymer.
• Colour: Blue.
• Density: Approximately 1.5g/cm³.
• Water solubility: Insoluble.
• Waterproofing performance: Up to 5 atm.
• Elongation at break: 70–100% according to ASTM 638 M-89.
• Temperature stability: -30°C to +50°C.
• Storage: 36 months in a dry place at temperatures between +10°C and +40°C.

Expansion Performance

Idrostop gradually expands when in permanent contact with water. The manufacturer's stated expansion figures are:

• After 24 hours: Approximately 45%.
• After 2 days: Approximately 70%.
• After 3 days: Approximately 82%.
• After 7 days: Approximately 120%.

Installation Guidance

The concrete surface must be clean and sound before Idrostop is installed. Remove cement laitance, dust and loose material. The profile can be applied to slightly damp surfaces, but it must not be installed while the structure is immersed in water. Remove free-standing water and allow several hours before installation.

Idrostop can be fixed using Idrostop Mastic, a ready-to-use MS polymer adhesive, or suitable mechanical fixings such as nails or screws.

• Using Idrostop Mastic: Apply the adhesive evenly and press the profile firmly onto the prepared substrate. Allow 24 hours before pouring the next concrete section.
• Reduced waiting time: Where necessary, the waiting time can be reduced to a minimum of 4 hours after applying Idrostop Mastic, with additional nails or screws placed every metre to prevent movement during the concrete pour.
• Using nails or screws: Fixings should be spaced no more than 25cm apart. Concrete can be poured immediately after mechanical fixing.
• Application temperature using Idrostop Mastic: +10°C to +40°C.
• Vertical installation: Mapei recommends installing the profile in lengths of approximately 1 metre on vertical surfaces.
• Concrete cover: The thickness of concrete protecting the installed Idrostop should be at least 8cm.
• Joint connections: The ends can be aligned end-to-end. Mapei also illustrates a 2–3cm staggered overlap for improved sealing.

Important: Do not install Idrostop on surfaces heavily contaminated with acids or solvents. Ensure the profile is correctly positioned and adequately confined within the concrete. Follow the manufacturer's current technical datasheet for the complete installation procedure.

Frequently Asked Questions

1. What is Mapei Idrostop used for?

Mapei Idrostop is used to waterproof construction joints in concrete structures. Typical applications include foundations, retaining walls, swimming pools, reservoirs, tunnels, dams and other civil, industrial and hydraulic structures.

2. How does Idrostop Waterbar work?

Idrostop gradually expands when in permanent contact with water. This expansion creates an active barrier within the concrete construction joint, helping to prevent water passing through the joint under hydraulic pressure.

3. What water pressure can Idrostop withstand?

Mapei states impermeability up to 5 atm under its test conditions. Actual performance depends on correct installation, concrete quality and the construction details surrounding the waterstop.

4. What sizes does Idrostop come in?

The sizes listed here are Idrostop 10 (20 x 10mm), Idrostop 15 (20 x 15mm) and Idrostop 25 (20 x 25mm). Each is supplied in boxes containing six rolls.

5. Does Idrostop contain bentonite?

No. Idrostop has an acrylic polymer base and does not contain bentonite. Its composition is designed to maintain its properties through repeated expansion and contraction cycles.

6. How do you fix Idrostop to concrete?

Idrostop can be fixed using Idrostop Mastic or suitable mechanical fixings. When using Idrostop Mastic, the normal waiting time before pouring concrete is 24 hours. Mechanical fixing with nails or screws allows concrete to be poured immediately.

7. Can Idrostop be installed on a wet surface?

It can be applied to slightly damp concrete, but it must not be installed while the structure is immersed in water. Remove free-standing water and allow several hours before fixing the profile.

8. How much concrete cover is required?

Mapei specifies a minimum concrete cover thickness of 8cm around the installed Idrostop profile.

Buy Mapei Idrostop Waterbar from Clever Shield

Clever Shield supplies professional Mapei waterproofing products throughout the UK, including specialist waterstops for concrete construction joints, basement waterproofing and hydraulic structures.

Order Idrostop 10, Idrostop 15 or Idrostop 25 for your next concrete waterproofing project. Contact our team for availability, pricing and delivery enquiries.

Technical Downloads

Idrostop is classified by Mapei as an article and does not require a Safety Data Sheet under the applicable REACH requirements.

Clever Shield supplies Mapei waterproofing products throughout the UK. We supply products and manufacturer documentation but do not provide project-specific waterproofing design or specification.