Vertical Movement from Floated Wood Floors


Vertical movement of flooring elements when under loading; often occurring with popping, or squeaking etc.


Floating Floors

In floating floors vertical movement is usually due to unevenness of the sub-floor. The flooring elements bridge a depression in the sub-floor and bend when under loading. This flexing of the floated flooring can lead to gaps opening, and over a period of time the surface veneer may split or delaminate, or the tongue may eventually break. Very minor vertical movement is sometimes unavoidable in floating floors and does not usually affect the performance of the floor.

  • Uneven subfloor
  • Curvature (convex shape) of the flooring itself
  • Header joints too close. Should be 300mm+ apart in most 14mm thickness engineered products

Solid Load-Bearing Floors

Header joints in adjoining rows may be too close, or end matching may be excessively loose. Thickness of the flooring element may be too thin for use as load-bearing floor leading to flexing between joists or batons.

  • Header joints too close (under 150mm apart or 3 or more in a row between supports).
  • Excessively loose end-matching.
  • Flooring not of load bearing thickness.
  • Joist or batons too far apart.
  • Excessively uneven sub-floor in combination with floating baton system.

Adhesive Fixed Floors

Vertical movement in bonded floors often coincides with a popping sound, and is usually caused by failure of adhesion to the sub-floor due to excess sub-floor moisture, insufficient contact between flooring element and the adhesive at time of installation, caused by unevenness of sub-floor or wrong trowel type. Surface contamination on the sub-floor or underside of the flooring element creating a barrier to good adhesion, a delay in the placement of the flooring element onto the adhesive can also lead to poor adhesion between flooring element and adhesive.

Failure of Adhesion Caused by:

  • Excessive sub-floor moisture.
  • Uneven sub-floor.
  • Wrong trowel type.
  • Wrong adhesive type.
  • Delayed placement of flooring onto adhesive.
  • Surface contamination.
  • Poor mixing of adhesive components.
  • Weakness of screed, or poor adhesion of leveling screed, epoxy DPM, etc.
  • Sub-floor materials unsuitable for direct bonding e.g. Magnesite, vinyl, asbestos, rubber etc.


Most of the causes of flexing / vertical movement can be diagnosed simply by observing the likely causes of this problem. Sub-floor moisture problems are best detected using insulated probes with a moisture metre, through holes drilled in the problem floor likely to be in excess of 14% WME. In adhesive fixed floors, flooring elements can be uplifted to check if flooring element has been in contact with adhesive.

  • Check for sub-floor moisture
  • Check contact between flooring and adhesive / sub-floor


With adhesive fixed floors and floated floors, adhesive can be injected into a hollow beneath the floor through a hole drilled in the floor followed by weighting of the flooring to help disperse adhesive (and maintain contact between the adhesive and the flooring element in non-floated floors). The hole through which the adhesive has been injected can be plugged or filled.

Where flooring is bonded to a wooden sub-floor, flooring can be face fixed with nail or screw. Alternatively where flooring is suspended and access can be gained beneath the floor, a pilot hole can be drilled through the wooden sub-floor and into the wood floor covering above and screwed into the hole which tightens down the flooring to the sub-floor.


Most aspects of installation are involved in avoiding vertical movement, from the evenness of sub-floor or spacing of batons, to the frequency of secret nail fixing or choice of trowel type when adhesive fixing.

Vertical Movement from Floated Wood Floors
  • A. Finished flooring is tightened down by screwing through pilot hole in the timber sub-floor into the flooring.
  • B. Flooring is secured by face nailing flooring to timber sub-floor and joist. Alternatively finished floor may countersunk, screwed, plugged and spot finished.
  • C. Loose, squeaking / tapping strip flooring is secured by injecting adhesive between finished flooring and sub-floor. The floor is then weight to disperse adhesive and maintain contact between flooring and adhesive, and the hole is plugged.