This site is not ready for delivery of flooring.

A wet and muddy crawl space
Head off problems before they start. Check the jobsite before installation, educate and advise your crews and subs on how to identify acceptable conditions as well as potential problems. Create a working relationship with the builder/general contractor and advise them on site conditions that promote good wood flooring performance and conditions that cause problems and call backs. Regardless of the outcome, call backs cost money. It will cost nearly $200 just to ring the customer's door bell to assess the situation. Many contractors/builders won't believe this figure but just think of the time involved, lost production, scheduling interference and good will. The call back could cost thousands if replacement of the flooring is demanded.

Calcium chloride test on a slab
But we all know call backs only happen to the other guy. Right? The builder/general contractor has to have the flooring done today, we have to get to the next job, the house is closing next month, and on and on. Even though the site is not ready, we install anyway.

With all that said, what issue results in the greatest number of call backs?

Unusual moisture conditions
Unusual moisture conditions are those that are different from the conditions expected when the space is occupied. This is why NOFMA installation instructions say a "near- occupied" environment must be established before the flooring is delivered to the site. What constitutes "near occupied" conditions? Near occupied means the structure is near enough to completion for construction-introduced extra moisture to have dried to normal conditions and that these conditions will remain through completion of the project. Sometimes running the HVAC equipment is necessary to reach these conditions, sometimes not. That means the structure is dried in, the windows and doors are installed and the dry wall has been mudded, taped and primed.

Check and mark the moisture reading of the slab.
In order to perform optimally, flooring should be near the environmental moisture content for the geographical area when installed. This condition should be maintained until occupancy when normal environmental conditions are established. Wet site conditions cause the flooring to expand. If already installed, cupping and or buckling can result. Sand and finish the cupped floor and -BAM!- A call back occurs when the flooring crowns and gaps as it dries to normal conditions. If flooring is installed after acclimating and expanding at the wet jobsite, shrinkage and abnormal gaps will result when drier normal conditions are established. Sometimes the gaps can be filled before finishing after all the extra moisture is removed; but if not done properly (i.e. filled completely from the tongue) - BAM! - A call back, jagged gaps with filler popping out.

Check the moisture of basement framing.
Require your crews/subs to use common sense and make observations before they install. They should check to see that: all windows and doors are in place; dry wall is up, taped and primed; site is not wet; crawl space is dry with a cover in place; basement is dry; etc. These observations point to a nearly completed structure without excessive moisture. Next, fine tune the conditions by checking the site with a moisture meter. Stick the subflooring and or test the slab. Test other wood materials, jambs, wall plates, return air framing, etc. Make 20 to 40 sticks; if the average reading is too high, don't install.

Check the subflooring, particularly at exterior doors.
Why check wood materials such as wood framing that is not directly associated with the flooring? The framing has been in place since building began and is slow to gain and loose moisture once the roof is on. Its moisture content will show environmental conditions of the previous weeks. If readings are too high, adverse conditions are continuing. This should be a red flag for future problems. If readings are OK and the subflooring is marginally higher, the indication is the interior environment is OK for the flooring and the subflooring is drying. If the subflooring is too high and the framing OK, check for a source of moisture like a wet crawl space, wet slab, rain wetted subfloor etc. These moisture sources will need to be eliminated and the high moisture reduced before flooring installation.

Crawl space covered 100 percent
The same checks should be made for slab construction. The surrounding wood components show how dry or wet the environment has been. Wood in contact with the slab can also show the slab's condition. However, the slab itself will have to be checked for extra moisture. This is also why the interior environment should be near occupied conditions. If the interior relative humidity is high it's like putting a lid on a pot, the moisture can not migrate out. Moisture meters generally give a relative reading for moisture within the slab. You should determine good readings for your area similar to the determination for average expected moisture content of flooring. Slab moisture checks with calcium chloride in the 3 lb. or less range are considered safe. Experience shows that the 3 to 5 lb. range is generally safe for solid wood flooring on a subfloor with a proper vapor retarder in place.

Flooring installed too soon is abused by everyone.
If an excessive or high moisture condition exists, the question arises, how to take care of the moisture and who will take care of the fix? Most site related moisture should be the responsibility of the general contractor/builder. If the crawl space is wet dry it out and install the appropriate ground cover. A wet slab or basement, dry them out. Heating or AC will accelerate drying. If necessary, start up the HVAC. The builder says the permanent system can't be operated until everything is finished. OK, air movement is a key component. The air handler is in place, turn on the fan. Normally, this does not require permanent hook up since the fan runs on 110 voltage. Also, an objection is that heating and air cost money. Well, so does the call back and repair. Running box fans in the house can reduce the moisture. Open windows at mid-morning during lower daytime humidity to evaporate moisture from wood components and create air changes. Close the windows at night to keep high humidity out, but keep the fans on to continually move the air. Drying can take five days or longer. How long? Re-check the wood components with a moisture meter. If within the proper range proceed with installation.

Moisture reading of framing
What moisture condition is too high? As a professional, you should know the average moisture content of subflooring and finished flooring of occupied homes in your area. Average moisture content for Memphis, TN, area is near 8.5 percent for finished flooring and 11-12 percent for subflooring. Average summer readings can be higher by 1-2 percent mc and winter readings lower by 1-2 percent mc. An average moisture content of the subflooring and other framing components above 13-14 percent would be too high. An average mc above 9 - 9 1/2 percent in the flooring would be too high. Of course the occasional piece of flooring might be 11 -12 percent and result in a gap after acclimation. This gap will be filled during finishing as a normal procedure. For other areas of the country the "too high" designation should be adjusted. Subflooring at 13 percent mc average would not work in Colorado; it would be too high. Subflooring averaging 14 - 15 percent mc would be ideal in Houston TX.

Take moisture readings of the slab.
We can sometimes work with elevated moisture conditions if they are actively being reduced. But, the elevated condition should not be excessive. Placing felt on top of the drying subfloor will help protect the flooring from the additional moisture until occupied conditions are established. The gaps resulting from drying will be minor and should be filled during finishing. Gaps resulting from a similar moisture change and factory finished flooring may become prominent and if filled may not be acceptable. We can also work with the too dry condition such as winter heating in the upper Midwest. Spacing the flooring during installation will probably be necessary. Field spacing will take care of the normal expansion expected during the summer.

This flooring was installed before wet work; it already needed an inspection when it was completed.
For good flooring performance avoid unusual moisture and moisture -related conditions.
• Be the professional; know your product and the average moisture conditions required of the product and the jobsite.
• Require near occupied environmental conditions before delivery.
• Make common sense observations
• Check jobsite conditions with a moisture meter.
• Educate your workers and builders.
• Do not even deliver product to sites with excessive moisture.
• Assess marginal conditions for change in the right direction.