Flooring defects

[edit] Introduction

A floor is a '...lower horizontal surface of any space in a building including finishes that are laid as part of the permanent construction.'

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.

[edit] Solid floors

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.

Downward movement in the slab is usually the result of consolidation of the hardcore fill beneath.

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.

[edit] Suspended floors

Failures in suspended timber floors, especially at ground floor level, are liable to be caused by timber infestation, either insect attack or rot.

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.

[edit] Raised floor

A raised floor (access floor or raised access floor) is a floor created above a solid floor slab, leaving an open void between the two. This void can be used to distribute building services.

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.

If the raised floor is incorrectly specified or installed, it may fail under loading.

[edit] Floor coverings

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.

Cracks may also appear at the junctions of any sheet material or insulation that is laid between the slab and the screed. Where overlaps occur, the screed will be thinner and more vulnerable.

A finish applied to a screed may provide the first clues to flooring problems. If a screed shrinks, any sheet fixed on top may develop ripples.

A floor surface will eventually wear out, either exposing the layer beneath, which may not have the same properties, or creating an unattractive finish.

Damage can also be caused to a floor covering through the use of inappropriate cleaning materials and methods. Sometimes a build up of cleaning materials can cause deterioration.

[edit] Find out more

[edit] Related articles on Designing Buildings Wiki

• Ash deafening.
• Bridging.
• Defects.
• Domestic floors: Part 1: Construction, insulation and damp proofing.
• Floating floor.
• Floor definition.
• Floor insulation.
• Flooring.
• Laitance.
• 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.