Help & Advice
Choosing either timber floors or concrete floors at intermediate levels are a matter of personal preference. Timber floors are generally cheaper than a concrete floor, though concrete floors have a couple of advantages. The first advantage is that a concrete floor will provide a much quieter house than a timber floor. Concrete floors have greater structural stability, and better resist side load pressures on the wall such as retaining earth or high wind loads. Some also prefer the concrete floor for under-floor heating.
The open-web timber floor is very good for running services within the metal frame between the two chords. These are ordered to the appropriate size, removing the need for onsite alteration. This floor structure can also accommodate larger services such as mechanical heat ventilation recovery systems. Not only do they have price advantage but they are usually simpler to install. Builders usually prefer them.
Timber floors have the advantage of being light weight, making them easier to handle on site. This should save the expense of hiring in a crane.
There are also several types of concrete floor to choose from, both pre-cast and cast in-situ. The most popular concrete floor is probably beam and block. These are pre-cast concrete beams laid between the walls at carefully calculated distances. The pre-cast hollow-core floor will achieve greater spans but will require a larger crane to lift the concrete planks into position. Remember to take care to plan voids for services. Later alterations that require concrete cutting equipment will prove expensive.
Of the cast in-situ options, the most common seems to be a structural metal deck floor, often called “wiggly tin”. Corrugated metal sheets made to suit the size of the span which the builder fastens these into position. He then lays down the reinforcement mesh and ties this to the wall reinforcement. Finally he pours concrete onto the steel sheets which thereby become the structure. The structural metal deck is permanent and remains in place.
There are some interesting hybrid solutions on the market that combine a pre fabricated concrete slab connected to a timber beam. These offer an alternative to timber floors or concrete floors, but for the moment these tend to be a relatively expensive option.
We do not recommend the use of polystyrene formwork intermediate floors. You don’t need insulation between upstairs and downstairs. And some of these systems have potential fire safety issues.