Just a few days following pouring of the foundation concrete, the sub-dpc structure is up and the beam and block flooring has been laid.
In instances where the foundation depths are inexcess of 1500mm a beam and block floor has to be used. This requires a void below which allows the soil to expand and contract without affecting the structural integrity of the extension. Additionally, and one of the reasons for always using a beam and block floor, this also provides an instant working platform for the site workers and for the storage of materials, which in itself speeds up the build time.
Visible, in the photo below, are the periscopic cavity ventilators which provide a clear unobstructed route for natural ventilation to the cavity below the suspended floor. Where the extension is obstructing the flow of air to an existing suspended timber floor additional vents would be installed, to connect to the existing floor vents via dedicated pipework, to maintain ventilation of the void beneath the existing suspended timber floor.