Understanding Type A and Type B Waterproofing - and Why It Matters

Below-ground waterproofing is one of the most critical elements of a building’s long-term performance. When it fails, the consequences can be costly, disruptive, and difficult to remediate. That’s why understanding the different waterproofing strategies - particularly Type A and Type B protection - is increasingly important for designers, engineers, and builders across New Zealand.

As British Standard (BS 8102:2022) continues to influence local expectations and best practice, there is a growing emphasis on selecting the right system, or combination of systems, based on risk, ground conditions, and intended use of the structure.

What Is Type A Waterproofing?

Type A waterproofing refers to barrier systems that are applied externally or internally to prevent water ingress. These are typically membrane-based solutions designed to form a continuous waterproof layer between the structure and the surrounding ground.

Common Type A systems include:

Bentonite-based membrane
Fully bonded and self-adhesive membranes
Bitumen membrane systems

Type A protection is widely used and highly effective when correctly designed and installed. It is often the first line of defence against ground moisture and hydrostatic pressure and plays a key role in many below-ground applications.

With the addition of Bituthene® and Preprufe® from GCP, alongside our Volclay and Swelltite bentonite membranes from CETCO, Allco now offers one of the most comprehensive Type A membrane range available in New Zealand.

What Is Type B Waterproofing?

Type B waterproofing is based on the concept of integral protection. Rather than relying solely on an applied barrier, the structure itself - typically reinforced concrete - is designed and constructed to resist water ingress.

This is achieved through:

Concrete design and detailing
Crack control
The use of waterproofing admixtures

Type B systems provide long-term durability by turning the concrete into a watertight barrier from within. They are particularly effective in complex below-ground environments where access for remediation is limited and durability is critical.

The introduction of Centrament Proof 10 (CP 10) from MC-Bauchemie marks Allco’s first move into integral waterproofing. CP 10 is a crystalline admixture added directly to the concrete mix, where it reacts to seal capillaries and pores, enhancing resistance to water ingress, chemical attack, and long-term deterioration.

Why Understanding the Difference Matters

BS 8102:2022 places strong emphasis on:

Assessing risk
Understanding ground conditions
Selecting appropriate waterproofing systems
Considering combined protection (Type A + Type B) where required

No single system suits every project. In many cases, combining Type A membranes with Type B integral waterproofing provides increased resilience, redundancy, and confidence - especially for high-risk or high-value below-ground spaces.

Understanding these distinctions early in the design process leads to better outcomes, reduced risk, and improved whole-of-life performance.

How Allco Is Positioned to Support the NZ Market

With our expanded range, Allco is uniquely positioned to support a complete below-ground waterproofing strategy.

We now offer:

A full suite of Type A membrane solutions, including bentonite, bitumen, DPMs, and fully bonded systems
Type B integral waterproofing through CP 10 crystalline admixture
Strong technical support to help select the right system for the right application

This wide range allows us to work closely with specifiers, engineers, and contractors to deliver solutions that are aligned with best practice, project risk profiles, and evolving standards.

Below-ground waterproofing is no longer about choosing a single product, it’s about delivering a coordinated system that performs over the life of the structure.

If you have any questions or need technical support please get in touch with our technical team tech@allco.co.nz