- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 02 Oct 2019
In construction, a floor void is typically a vertical opening or hole that is left in the floor construction either to accommodate services, or allow the installation of a staircase or, as an aesthetic feature.
When services such as pipework, ducts and cables are required to penetrate vertically through a floor construction, a void must be created at the time of construction otherwise costly and disruptive remedial work must be undertaken. To avoid this, architects and engineers usually delineate on their drawings where floor voids are to be located.
With in-situ-poured concrete floors, voids need to be trimmed (with appropriate reinforcement within the floor thickness) around the opening and the necessary formwork installed to create the size and shape of void required. When the concrete is poured and the formwork eventually removed, a void remains.
Small vertical holes can be formed not only by timber boxes, which are usually removed after casting, but also by other materials such as polystyrene and stiff cardboard, which may be left in position.
Sometimes, when no provision for a void has been made, and the concrete has been poured, it is possible (for small service voids), to cut the holes after the concrete is cast. However, this is uneconomical and disruptive.
With precast concrete planks and beams, depending on the size of the void, special factory-made units can incorporate a hole in the beam or plank; alternatively, for larger voids, a system of shorter planks and mild steel supporting straps or trimming beams can be used to ‘trim’ around the edge of the void.
The term floor void can also be used to refer to the horizontal space between a ceiling and the floor above, which may accommodate the floor structure, services and so on. It may also refer to the void between the bottom floor of a building and the ground below, sometimes referred to as a crawl space.
 Related articles on Designing Buildings Wiki
Featured articles and news
Brick slip soffit systems and intricate brick features.
Breaking down possible steps of pre-contract management.
ICE event includes comments from Welsh Government Minister Julie James.
How to write them and what they should include.
Designing Buildings Wiki becomes the world's first website to adopt the new knowledge standard.
Assessing the most beneficial design elements.
Exploring different types of vinyl flooring.
New Government task force will build beauty into reformed planning process.
Five outstanding aspects of the profession.
The seismic strengthening of historic churches.
Results show guarded optimism and payment concerns.
Noteworthy navigable aqueducts.