In the UK construction industry, bimortar—commonly referring to BI Mortar Plaster Seal (BMPS)—has become a trusted name in advanced waterproofing. Manufactured by Volteco S.p.A., part of the global Soprema Group, this high-performance cement-based waterproofing plaster is widely used across Britain for basements, foundations, lift pits, and flood-prone structures.
With the UK waterproofing market valued at £500+ million annually (2025–2026) and increasing flood risks across regions such as the Midlands, London, and coastal areas, products like BI Mortar Plaster Seal are essential for compliance with BS 8102 and Part C of the UK Building Regulations (Resistance to Moisture).
This comprehensive 2026 UK guide explains everything you need to know about bimortar, including composition, performance, applications, safety, pricing, and supplier information.
1. What Is BI Mortar Plaster Seal (Bimortar)?
BI Mortar Plaster Seal (BMPS) is a single-component, cementitious waterproofing mortar designed to create an impermeable barrier against water ingress in construction and renovation projects.
Unlike traditional mortar, bimortar incorporates water-repellent additives and advanced bonding agents, making it suitable for both positive and negative hydrostatic pressure applications.
Brand & Manufacturing Background
- Developed by Volteco S.p.A. (Italy, founded 1976)
- Acquired by Soprema Group in 2018
- Distributed in the UK via Soprema UK Limited
Volteco is recognised internationally for innovative waterproofing technologies, now adapted for UK climate and compliance standards.
Product Classification
- Type: Waterproofing plaster mortar
- Form: Grey powder
- Packaging: 25kg bags
- Application: Interior and exterior
- CE-marked and compliant with EN 1504-3
2. Composition, Technical Properties & Performance
Chemical Composition
BI Mortar Plaster Seal primarily contains:
- Portland Cement (24–29%)
- Zinc Stearate (1–3%)
- Mineral aggregates and bonding additives
Key Technical Data:
- pH: 11.4 (alkaline)
- Density: 2.99 g/cm³
- Compressive Strength: >25 N/mm² after 28 days
- Adhesion Strength: >1.5 N/mm²
- Hydrostatic Resistance: Up to 5 bar
Waterproofing Performance
Bimortar creates a 2–5mm thick impermeable layer that:
- Resists groundwater pressure
- Prevents efflorescence
- Stops salt migration
- Reduces mould formation
It is also vapour permeable (μ < 15), allowing trapped moisture to escape — particularly important in older UK properties and heritage restorations.
Why It’s Ideal for UK Climate
The UK experiences:
- High rainfall
- Freeze-thaw cycles
- Rising groundwater levels
- Flood risks in urban areas
BI Mortar Plaster Seal is engineered to withstand these environmental pressures while remaining breathable.
3. Applications of Bimortar in the UK
BI Mortar Plaster Seal is widely used across residential, commercial, and infrastructure sectors.
Residential Applications
- Basement waterproofing
- Cellar damp-proofing
- Bathroom and wet room sealing
- Foundation protection
- External retaining walls
Commercial & Infrastructure Uses
- Underground car parks
- Lift pits
- Tunnels
- Bridge structures
- Raft foundations
- Open basement excavations
In flood-risk zones such as the Thames Valley and Midlands, bimortar is frequently specified in compliance with BS 8102:2022 for below-ground waterproofing.
Heritage & Restoration Projects
Due to its breathable properties, BI Mortar is suitable for:
- Listed buildings
- Historic masonry
- Conservation areas (in line with Historic England guidelines)
4. Installation & Application Guide (UK Best Practice)
Surface Preparation
- Remove dust, oil, and loose debris
- Mechanically remove salts/efflorescence
- Pre-wet absorbent surfaces (no pooling)
Mixing Instructions
-
Add 5–6 litres of clean water per 25kg bag
-
Mix mechanically for 3–5 minutes
-
Achieve lump-free consistency
Application Process
- Apply using trowel or spray
- Install in 2–3 coats (total 3–5mm thickness)
- Wait 4–6 hours between coats
- Cure for minimum 7 days
Coverage Rate:
-
Approx. 1.5kg per m² per mm thickness
Health & Safety (UK Regulations)
BI Mortar Plaster Seal is classified as hazardous under UK CLP regulations:
- Causes skin irritation
- Risk of serious eye damage
- Respiratory irritant
Always use:
- Protective gloves
- Goggles
- Dust mask (FFP2 or equivalent)
Follow COSHH regulations and dispose of waste via Environment Agency-approved procedures.
For emergencies:
-
UK National Poisons Information Service (NPIS): 0344 892 0111
5. UK Distribution, Pricing & Market Position
UK Headquarters
Soprema UK Limited
Lady Lane Industrial Estate
Hadleigh, Ipswich, Suffolk
IP7 6BA
Phone: +44 (0)1473 822093
Website: soprema.co.uk
Where to Buy in the UK
Available through:
- SIG Roofing
- Travis Perkins
- Jewson
- Specialist waterproofing distributors
- Approved Soprema dealers nationwide
Pricing (2026 UK Estimates)
- 25kg bag: £35–£65 (depending on distributor and volume)
- Professional installation: Varies by project scale
Annual UK demand for waterproofing mortars exceeds 50,000 tonnes, with Soprema holding an estimated 10–15% share in specialised waterproofing products.
6. Industry Reputation, Reviews & Sustainability
Industry Reputation
BI Mortar Plaster Seal is considered a premium waterproofing solution in the UK market.
Recognised for:
- Durability
- High adhesion in damp conditions
- Long-term reliability
- Compatibility with modern building standards
It is often compared with:
- Sika waterproof mortars
- CEMEX waterproof cement products
- SikaProof membrane systems
User Reviews
On UK trade forums:
- Average rating: 4.5/5
- Praised for: Adhesion strength, waterproof reliability
- Criticised for: Requires proper mixing technique
Sustainability & Green Building
Supports:
- BREEAM projects
- Low-VOC construction
- Net-zero building strategies
- Compliance with UK REACH regulations
With the Building Safety Act 2022 pushing stricter compliance standards, waterproofing solutions like bimortar are increasingly specified in structural design.
Conclusion
In 2026, Bimortar (BI Mortar Plaster Seal) stands as a leading waterproofing solution within the UK construction sector. Manufactured by Volteco and distributed through Soprema UK, it offers:
- High hydrostatic resistance (up to 5 bar)
- Excellent adhesion and durability
- Breathable moisture control
- Compliance with BS 8102 and UK Building Regulations
- Proven performance in British climate conditions
Whether for basement conversions, flood defence infrastructure, or heritage restoration, BI Mortar Plaster Seal remains a trusted choice for professionals seeking long-term structural protection against water damage.
Frequently Asked Questions (FAQs)
1. What is bimortar used for?
It is used for waterproofing basements, foundations, lift pits, and below-ground structures.
2. Is BI Mortar compliant with UK regulations?
Yes, it supports compliance with BS 8102 and Part C of UK Building Regulations.
3. How waterproof is BI Mortar Plaster Seal?
It resists hydrostatic pressure up to 5 bar.
4. Can bimortar be used externally?
Yes, it is suitable for both interior and exterior applications.
5. Is professional installation recommended?
Yes. Due to its chemical properties and structural role, trained professionals should apply it.
