Unchecked Moisture Can Lead to Flooring Install Failures

Posted by PAUL LAURENZI on May 13, 2015 12:30:00 PM

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Another year, another successful NWFA Wood Flooring Expo! This year I presented “How Moisture Claims Can Drown Your Profits” educational seminar to a full house of over 100 professionals interested in learning how they can improve their wood flooring installation or inspection business by having a better understanding of on the job moisture matters.

The topic spurred a great discussion about effective use of moisture meters so we thought it would be valuable to share the key takeaways with those who were unable to attend.

Flooring Failures + Callbacks + Lost Time = Lost Profits!

Some estimates indicate that moisture related issues account for an astounding $1billion in flooring failures and claims. How can you prevent these failures and the associated loss of profit? One way is to use a moisture meter to: 

  • Measure moisture content (MC) in the wood floor and the subfloor
  • Assess water damage
  • Test relative humidity (RH) and moisture in concrete
  • Monitor the curing process
  • Determine equilibrium moisture content (EMC) and optimum conditions

Ideal Conditions for Installation

ideal conditionsWood is hygroscopic. When exposed to the air it will lose or gain moisture until it is in equilibrium with the humidity and temperature of the air. Because of this, wood flooring needs to be installed at the MC where it will not change dimension or experience defects.

This optimum level of temperature and RH is referred to as the equilibrium moisture content (EMC). To measure RH you’ll need a thermo-hygrometer, as equally an important tool to have on hand for an installer as a moisture meter.

EMC varies across the country though 6% – 9% will cover most areas of the US. Wood subfloor should be within 2% - 4% MC of the flooring being installed.

Moisture Meter Types – Pin vs. Pinless

Pin meters have electrodes that penetrate the wood to measure the electrical resistance or current between two points of contact. They use the relationship between the DC resistance and the MC of the wood.  Measuring with a pin meter will provide accurate estimate of average MC, give a good idea of the moisture gradient, and identify whether the source of moisture is the top floor or the subfloor.

Pinless meters transmit electromagnetic wave energy into the wood to detect the influence on moisture as an estimate of MC. It does this by sending a radio frequency (RF) wave into the wood but models may differ in frequency and electrode design. In the building trades, they are excellent tools for gaining an overall sense of the moisture condition.

Factors That Can Affect a Meter Reading

Because meters provide indirect measurements, the accuracy and reliability of their readings are subject to a number of factors. The major ones are outlined in an effort to help you decide which type best suits your needs. 

 

Pin Meter

Pinless Meter

Wood species

  • Correction factor required
  • Regional differences can be an issue
  • Species correction is a factor of specific gravity
  • Source differences

Specific gravity (density)

  • No correction required
  • Meter readings must be corrected for effect of SG
  • SG values in literature are variable (regional differences)

Wood temperature

  • Meter readings affected by wood temperature and must be considered under conditions other than testing at normal indoor ambient conditions.
  • Meter readings are affected but not to the same extent as DC resistance.

MC Range

  • Accurate results within 6 to 25% range (below FSP)
  • Readings outside this range are a relative indication of MC
  • Useful results below FSP
  • Readings down to 5%

Surface moisture

  • Will not affect reading if insulated pins are used and in good condition.
  • Can still detect for presence of wet surface by touching pins
  • Has an influence on MC estimates obtained
  • May cause to over-estimate average MC

Sample size (width and thickness)

  • Meter readings not affected by sample size
  • Meter reading is very specific to wood between tips of pins
  • Thickness is compensated for by pinning depth
  • Board needs to be as wide or wider than sensor plate.
  • Meters have depth of penetration limit.
  • Be conscious of material behind sample when testing thin material.
  • Reading may not penetrate to core on materials over 2" thick.

 

 

 

Moisture Meters for Flooring

Moisture meters and thermo-hygrometers are proven, indispensible tools for flooring inspection and installation. To achieve fast, accurate results you must know the meter’s capabilities, follow the manufacturer’s procedures and, most important, apply your knowledge and experience. 

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Topics: Wood Flooring Moisture Content Flooring NWFA moisture meters Equilibrium Moisture Content EMC moisture meter manufacturer Flooring Failures RH

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