Building foundations with aircrete

A foundation distributes the weight of a building to the ground so it needs to be of the highest quality and reliability in order to provide stability to a building.

The lighter weight and faster build-speed of Celcon Blocks enables a building's foundations to be constructed quickly, easily and cost-effectively.

Regular Celcon Blocks can be used below the DPC to form both the internal and external leaves of cavity foundations.

For an even faster build, Celcon Foundation Blocks of 275mm thickness and upwards can be used to form solid foundation walls. This method is fast as only one wall has to be set out and there is no need for wall ties or a lean mix fill.

Historically, poured (mass fill) concrete foundations were common. These can be expensive with the cost of concrete dependent on the volume of trench excavated. Sometimes a hybrid foundation is used to reduce costs with poured concrete is used to form footings followed by a minimum of two courses of Celcon Foundation Blocks laid on top. The effect is both to reduce costs and enhance the thermal efficiency of the ground floor.  

Advantages of aircrete foundation blocks

Celcon Foundation Blocks can support both solid and cavity wall constructions along with timber and steel-framed systems. Blocks are available in a range of face sizes and thicknesses to ensure the foundation is at least as wide as the thickness of the wall being supported.

  1. Thermal performance
    Aircrete's cellular structure, durability and thermal insulation properties make it an ideal material for use in foundations. Its enhanced thermal performance helps reduced heat loss from ground floors and, more importantly, significantly reduces linear thermal bridging at the floor junction (psi value). 

    In addition, the raw materials used in the production of Celcon Blocks give them excellent resistance to sulfate attack and frost damage. Foundation blocks are suitable for use in soil conditions from Design Sulfate Class 1 to Design Sulfate Class 4.

  2. Speed
    Celcon Foundation Blocks help improve productivity. They are lightweight, weighing one-third of an equivalent dense aggregate block, which makes them easier to handle and lay, improving productivity. Solid foundations mean fewer materials on site and their greater workability means they can easily be cut with a hand saw. Ease of workability means off-cuts can often be incorporated into the build, reducing wastage.
  3. Cost
    When laying like for like 7.3N blockwork foundations, the benefits of laying the lighter Celcon High Strength Grade Foundation Block can result in a 23% cost saving. And, if the Celcon Standard Grade solid foundation blocks are used, cost savings can be as high as 26%

    Unless the foundation blocks form a retaining wall or basement wall, further time and material savings can be achieved by the omission of mortar from the vertical joints (perpends) in solid foundations, provided the blocks are butted close together to stop the passage of vermin.

    Further cost and time savings can be achieved using the Foundation Block system because it enables the foundation trench to be back-filled as soon as the foundations have been completed, allowing construction to progress immediately.

  4. Health and Safety
    There are also be health and safety benefits from handling lighter blocks and reduced wastage. Most thicknesses/sizes are below the CONIAC handling regulations, reducing the risk of injury.
  5. Approved method
    Celcon Foundation blocks are approved by the British Board of Agrément (BBA) for use below DPC.

H+H products for the construction of foundations

H+H aircrete Foundation Blocks are available in Standard Grade (3.6N/mm2) and High Strength Grade (7.3N/mm2) to support buildings up to three storey buildings.

The blocks are available in two face sizes 325 x 215mm and 440 x 215mm. The 440mm face size block is available in three thicknesses: 275mm, 300mm and 355mm.

H+H Standard Grade and Solar Grade aircrete blocks can also be used below the DPC for both the internal and external leaves of cavity foundations. For applications where a higher compressive strength is required, such as the foundations of three and four storey buildings, H+H's High Strength and Super Strength Grade blocks should be used.

Below ground, M6 mortar should be used where there is a risk of freeze/thaw or in some circumstances M4 mortar may be used depending on soil conditions.