Aggregate
Industries is urging housebuilders to look more closely at the technical
considerations before installing block and beam flooring, as the 1st January (2018) deadline for the National
House Building Council’s (NHBC) Technical Extra 20 standard draws closer.
Originally
announced last year, the new standard states 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 to the NHBC.
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, Managing Director 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.
