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Last edited 11 May 2020
Flooring usually consists of a structural element and a finish which covers the structure. This finish could be attached to the structure (such as a screed), or merely covering the structure (such as carpet).
Floors will either be solid ground or suspended. Suspended floors could be at ground or upper floor level. They are generally constructed of timber or concrete, either in-situ or pre-cast. Generally, defects in suspended floors arise from deflection or attack by fungus or insects. Problems in upper floors can also occur where a building has been subjected to a change of use, or where there is insufficient insulation to combat noise, especially impact sound transmission.
Ground floors will either consist of a suspended floor, or of a solid slab, built directly off the ground. Defects may cause a slab to sink, or to lift. Signs of failure in a solid slab which is sinking include:
- Gaps between the underside of skirting boards and the solid floor.
- Cracks adjacent and parallel to perimeter walls.
- Cracks in partition walls built off the slab.
If a solid floor slab is damp it may be due to faults in the damp proof membrane (DPM). The location of the damp may provide clues, as will a note of when the damp manifests itself. Impervious floor coverings such as tiles may start to lift. Pervious materials such as carpet may be found to have mould growth on their underside.
Deflection or movement in suspended floors may be caused by inadequate joists or by joists at incorrect centres. Changes of use can result in increased loadings, particularly in older buildings. Excessive deflection can cause the outer walls to bow.
In theory there should be no such problems with concrete suspended floors because they will usually have been designed by a structural engineer. However, poor workmanship during construction can result in a floor that does not achieve its design strength. If shuttering is struck too soon then excessive loading may weaken the floor.
If there are defects in the structure below, or in the make up of the raised floor, panels can rock, or joints can separate, creating a potential hazard, and in some cases damaging services. Problems can also occur if the sub-floor is not level, if there is debris in the void, or where very small panels are necessary because of the alignment and spacing of perimeter walls.
A power float is a hand-operated machine used to produce a smooth, dense and level surface finish to insitu concrete beds. The use of a power float to provide a finish for an in-situ reinforced concrete floor can result in problems if insufficient curing time is left after pouring. Shrinkage of the floor can result in random cracking.
 Find out more
 Related articles on Designing Buildings Wiki
- Ash deafening.
- Domestic floors: Part 1: Construction, insulation and damp proofing.
- Floating floor.
- Floor definition.
- Floor insulation.
- Latent defects.
- Patent defects.
- Raised floor.
- Remedial work.
- Resilient flooring.
- Schedule of defects.
- Separating floor.
- Sistering floor joists.
- Sprung floor.
- Suspended ceiling.
- Timber preservation.
- Types of floor.
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