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, 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.
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 - see the Benfield ATT site
The Finished Floor
Having laid either a solid or suspended floor, there are a number of options for preparing for the finished floor. The main contenders are a screeded floor and a tongue and groove particle board (chipboard) floor.Screeded Floor
Generally this requires 2" or 3" of cement screed. This is often the preferred method if underfloor heating is required (although underfloor systems can also be put under wooden floors) but some people prefer a screeded floor anyway as it gives a firm, solid floor. Another advantage is that it is quicker (than a chipboard floor) to lay. However, a screed will take a long time to dry and the extra moisture in the air may delay the installation of wooden internal doors - which may distort in the presence of a moist amosphere.There are two options for laying the screed
- a (traditional) sand/cement screed, mixed and laid by hand
- a pumped readymix self-levelling screed
