Hebel Block — Autoclaved Aerated Concrete Blocks, Sydney

What is Hebel Block?

Hebel Block is also known as an AAC block or autoclaved aerated concrete block. It's a precision-cut masonry block manufactured from a mixture of sand, lime, cement, and a gas-forming expansion agent. During production, the mixture is aerated to form millions of fine, closed air pockets, then steam-pressure cooked in an autoclave oven to harden.

The result is a block that is strong, dimensionally accurate, and approximately one-fifth the density of standard concrete.

CSR Hebel is the only manufacturer of AAC in Australia and has been producing Hebel since 1990. The product is specified by architects and builders across Australia for its combination of thermal performance, fire resistance, acoustic insulation, and construction speed.

Hebel Block is laid like a standard masonry block using a thin-bed adhesive mortar (not a standard cement mortar), with cuts and shapes made using standard circular saws or hand tools.

Specifications

Contact Martins at (02) 9651 1055 to confirm current block sizes and stock availability. Sizes and pricing are subject to change.

What is Hebel Block Used For?

Hebel Block is used wherever a masonry wall system is required, but the builder needs to reduce dead load, improve thermal performance, or speed up construction. It is suitable for both loadbearing and non-loadbearing applications.

Loadbearing External Walls

Hebel Block can be used in loadbearing external wall construction for residential and commercial buildings up to three storeys. It replaces double brick construction while delivering significantly better thermal resistance, approximately three times better than double brick, and is faster to lay due to the larger block size and thinner mortar bed.

Non-Loadbearing Internal Walls

For internal partition walls, Hebel Block delivers excellent acoustic separation between rooms; a key advantage in multi-residential and commercial builds where sound transmission between spaces needs to be controlled.

Rendered Fence Panels and Boundary Walls

Hebel Block is widely used for garden walls, boundary fences, and rendered fence panels. Its ease of cutting and shaping with a standard saw or hand tools makes it well suited to curved walls, feature panels, and custom heights.

It is also used alongside a Slip Joint / Sliding Joint at slab interfaces and panel junctions to accommodate vertical movement in the wall; a requirement for compliant masonry construction.

Works alongside: Slip Joint / Sliding Joint, Foam Joint Adhesive, Building Materials range

Fire-rated Wall Systems

Because Hebel Block is non-combustible, it is specified in fire-rated wall applications including party walls between dwellings, external walls in bushfire-prone areas, and commercial separating walls. It meets the requirements for fire resistance under the National Construction Code.

Noise Barriers and Acoustic Walls

The cellular air pocket structure of Hebel Block gives it strong acoustic absorption properties. It is used for noise barrier walls along roads, in commercial precincts, and between residential properties where acoustic separation is a performance requirement.

Hebel Block vs Standard Concrete Block: What's the Difference?

For most residential new builds and renovations where thermal performance and construction speed are priorities, Hebel Block is the stronger specification.

For applications where maximum compressive strength is the primary requirement and weight is not a concern, a standard dense concrete block may be more appropriate.

How to Lay Hebel Block

Hebel Block is laid similarly to standard masonry block, with two key differences: the mortar bed is thin (2-3mm of AAC adhesive, not a standard 10mm cement bed), and the blocks are butted tight at vertical joints rather than mortared.

1. Prepare a standard concrete footing or floor slab to receive the first course.
2. Set out and lay the first course in a standard cement mortar bed to level and establish the datum.
3. From the second course up, apply Foam Joint Adhesive (AAC thin-bed adhesive) to the top face of the previous course using a notched trowel or applicator.
4. Lay the next Hebel Block course, butting blocks tightly at vertical joints with no mortar between them.
5. Check for level and plumb on each course. Hebel Block can be ground back with a float or rasp to correct minor level variations between courses.
6. Cut blocks to length or shape using a standard handsaw, circular saw, or angle grinder with a masonry blade.
7. Once the wall is complete, fix Render Angle Corner beads at all external corners before applying a proprietary render or AAC-compatible primer and paint directly to the block face.

For full installation guidance, refer to the CSR Hebel installation manual. Our team at Martins can advise on compatible adhesive products and render systems.

What is Hebel Block Not Suitable For?

Hebel Block should not be used below ground or in permanently wet conditions without appropriate waterproofing treatment; its porous surface will absorb moisture if left uncoated in below-grade or submerged applications.

It is also not suitable for use with standard cement mortar at bed joints above the first course; use Cement S&C only for the datum bed on the first course, then switch to the correct AAC thin-bed adhesive from the second course up. Using standard mortar throughout will compromise joint strength and thermal performance.

Hebel Block should not be rendered with a standard sand and cement render without checking compatibility. A proprietary AAC-compatible render or base coat is required to prevent cracking and delamination.

Not sure whether Hebel Block is right for your application? Call our team at (02) 9651 1055, and we'll help you work it out.

Hebel Block Availability — Sydney Supply from Dural

Martins BLS stocks Hebel Block at our Dural yard, servicing builders, concreters, and owner-builders across the Hills District, Hornsby, Parramatta, Blacktown, and the wider Sydney metro area.

We've been supplying Sydney's building industry since 1970 and carry the full range of complementary products, including slip joints, geotextile fabric, and cement products (like agpipe and recycled crusher sand), to support your build from the ground up.

Call us at (02) 9651 1055 to confirm current stock, available block sizes, and pricing before ordering. Large orders can be arranged for direct delivery by tipper or crane truck.

Frequently Asked Questions