The Self Build Self Help Site Floor design
Floor design

Suspended Floor

Block and beam

The most common type of suspended floor is "block and beam", where concrete beams are laid between the external and internal walls. Concrete or lightweight blocks are then laid between the beams and gaps subsequently filled with a cement wash. Suspended floors are most used where the space above the ground is more than 600mm - or where the builder prefers that type of construction.

Advantages are ease of construction (although this is a matter of opinion), and avoidance of filling a large space with a large amount of infill. Current insulation requirements will probably mean you will need insulation blocks, with polystyrene or cavity insulation on top. Get the amount worked out accurately if you are not using insulation blocks for the wall construction - less waste.

For photos and explanation of the construction of block and beam, go to this Hints & Tips page.

Sub header photo of suspended floor

Sub header photo of suspended floor

This construction is often referred to as "Bison beam" - Bison is one manufacturer of the beams and so is used as a generic term. Find out more at the Hanson site and the Carter Concrete site for more information.

With block and beam the only option for the insulation is to place it on top of the beams.

It is more likely that the architect will have drawn the foundation plan so that every internal wall will be built from a foundation, unless extra strong beams have been specified to carry some internal walls.

Before you receive the beams, ensure that you have sufficient space to accomodate them, and that you can get the plant to them. The concrete beams are heavy so it is at least a two man job - 5m beams require 4 people to put them in place - and you may well need to crane the beams onto site and then into place - but a solid floor is also very hard work.

Structural floor cassettes

Another option is - large pre-formed concrete slabs that are craned into place.

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