My good friend, Ray Thompson who writes for Floor Covering Installer, and I were having this conversation regarding the benefits of having the proper heat for the installation of floor covering. So we decided to make this an article that will be published in an upcoming Floor Covering Installer magazine article.
In today’s world of new construction, it is a constant fight to control the temperature of the jobsite. Fast track construction has pushed the flooring world backwards, as flooring con-tractors face the daily battle of trying to obtain recommended job site conditions from the flooring, adhesive, and patching manufacturers. When the flooring contractor gets on the jobsite to install the flooring, the permanent windows and doors might not yet be installed, let alone the HVAC system be up and running.
Why is having the HVAC up and running so important? Let’s take a look at this from the ground on up. After the concrete is poured, with a vapor retarder in place directly beneath the slab, without a controlled air space the drying time of the concrete can be greatly ex-tended. If the air in the newly constructed building is saturated with moisture, the saturated air can hold very little excess moisture. This will affect the evaporation of the concrete’s mix water the newly poured concrete can get rid of and slow the drying process down. Drying and stabilizing out the newly constructed buildings air space allows the concrete to get rid of the excess water mix water and begin the drying process.
We don’t put wash out to dry on a damp/wet day do we? Why, because it won’t dry under these conditions….either will concrete or the other subfloors we install on.
Poured Gypsum Underlayments require; before, during and after installation, building inte-rior shall be enclosed and maintained at a temperature above 50 degrees F and below 100 degrees F until structure and subfloor temperature are stabilized. General Contractor shall provide continuous ventilation and adequate heat to rapidly remove moisture from the area until the gypsum underlayment is dry. Again, if the air is saturated with moisture, it can ab-sorb little no moisture being emitted from the gypsum underlayment.

Moisture testing requires a controlled air space. The Calcium Chloride (ASTM F1869-98) states; site should be same temperature and humidity expected during normal use, but if not possible, then 75 + 10 degrees F and 50 + 10% relative humidity.
The RH Probe (ASTM F2170-02) states; Concrete slabs shall be at service temperature and air space above the floor slab shall be at service temperature and relative humidity for 48 hours prior to measuring concrete RH.
If these conditions are not met, the saturated air cannot hold any more moisture which affects how the concrete can get rid of the excess water. Have you ever run a Calcium Chloride test and get an acceptable reading and then run the RH Probe test and get a very high reading? The reason for this is that the air is saturated and does not allow the slab to emit the extra water and gives you a low Calcium Chloride reading which reads the amount of moisture being emitted from the concrete. The slab is retaining the extra water which gives you a high RH Probe reading.
Patching compounds, self leveling underlayments and adhesives also require a tem-perature range to be installed within. If it is cold and damp, it retards the drying and cur-ing process of these products and does not allow them to dry and cure properly before installing the floor covering.
Flooring is greatly affected by temperature. To cold and it is stiff, can crack and break, and it can shrink when cold. To warm, it is very soft and tends to grow. Having the build-ing at service conditions is ideal for flooring installation. 40° F is not service conditions. Acclimation is key to flooring products prior to installation. Let the products get used to the environment they will be installed in 60 – 70 degrees.
Having temporary heat in buildings can also affect the drying of the subfloors. Propane heat can add more moisture into the air. A 20-lb. cylinder of propane adds 3 gallons of moisture to the air. Diesel and kerosene add almost a gallon-to-gallon burned. Tempo-rary heat systems tend to heat the air, but the slab remains cold as the hot air rise. The relative humidity can remain high retarding the drying of the environment.

Having the HVAC up and running stabilizes the building environment and allows things to dry and cure properly.
That is why I think slab temperature is so important. It is the true temperature of the slab and not the ambient temperature of the room. There is no telling when the ambient tem-perature was turn on and left on. Then we conduct tests that require relative humidity of the slab to be a certain stage which can be thrown off by temperature and humidity.
I have had experience with jobs with temporary heat and found the concrete dry near the heaters but wet away from the heaters. The contractor showed a since of disbelieve but the testing was accurate. In all directions the out come was the same.
With LEED projects, they don’t permit the use of the permanent HVAC units until the oc-cupancy of the building. That is a shame as they do the flooring professional an injustice, and I think that ought to change. However, the use of a temporary HVAC system not util-izing propane, diesel, or kerosene can be written into the building specifications which would meet the flooring industry’s request for constant temperature.

Special Thanks to JJ Haines for the Info