Housebuilders are being urged to look more closely at technical considerations before installing block and beam flooring.
Aggregate Industries warns that the 1st January deadline for the National House Building Council’s Technical Extra 20 standard draws closer. It says that when installing a block and beam type system the use of micro fibres as an alternative to steel mesh reinforcement, is now no longer acceptable.
Instead, approved macro structural fibres or steel fibres are deemed acceptable for use as reinforcement. According to the guidance, structural toppings on insulating block and beam systems requiring approval by the NHBC must use one of the following reinforcement options; macro ‘structural’ synthetic fibres, steel fibres or steel mesh reinforcement.
Chris Hudson, MD for Asphalt and Readymix at Aggregate Industries, said: “There is no doubt that the methods used to construct new floors have come on in leaps and bounds in the last decade. However, block and beam floors still remain the most popular solution for housebuilders when building a ground floor – and so it’s important that they are in-tune with the latest guidelines.
“In order to stay ahead of the game and iron out teething problems housebuilders should already be well underway in adopting these changes. However, there are a number of considerations that must be taken into account – and housebuilders must be aware of the implications – which is where starting conversations early doors with suppliers will come in handy.”
Chris gives his top tips for housebuilders when selecting concrete for block and beam flooring:
- Speak with your materials supplier of choice for advice. They can help you to understand the product limitations and unique benefits, and in some cases create a bespoke product where required.
- Select the appropriate types of pre-cast concrete beam and block to suit the structural and thermal requirements of the suspended floor construction and ensure that the beam type is compatible with the block type specified, in accordance with BS EN 15037.
- Ensure that the design of the concrete topping is structurally suitable for use with the beam and block system specified, and in line with the systems BBA approval.
- Be aware of NHBC restrictions on use of possible alternatives to welded steel mesh reinforcement for structural concrete toppings (e.g. steel fibres and Class ll synthetic polymer fibres and that NHBC does not accept the use of Class l synthetic polymer fibres as replacement for welded steel mesh reinforcement in a structural in-situ concrete topping.