HARDWOOD
  CONSULT THE MANUFACTURER IN ALL CASES FOR  COMPATIBILITY AND INSTRUCTIONS
Run the heating system at least 72 hours before accepting delivery of the hardwood flooring.                                                               
Open the hardwood flooring up and condition the flooring for 72 hours before installing.
Keep track of where the floor joists are for nailing purposes.                         
CARPET
              CONSULT THE MANUFACTURER FOR COMPATIBILITY AND INSTRUCTIONS
YOU MUST CONSIDER CARPETS ABILITY TO CONDUCT HEAT 
Most carpets and pads are compatible with radiant but a few are not.
LINOLEUM
              CONSULT THE MANUFACTURER FOR COMPATIBILITY AND INSTRUCTIONS
It is very rare but some linoleum's will discolor or put off a bad odor when installed over radiant.
CERAMIC TILE
Ceramic tile installs very well over radiant with excellent results.
Great tile floor resource at   www.ontariotile.com
MAKE SURE THE ADHESIVE IS COMPATIBLE WITH RADIANT HEAT

Hardwood floors can be used over a hydronic heating system if extra time and care is used during the installation process. Wood floors are what we call hydroscopic. That means the wood reacts to water, in much the same way a sponge does. If the wood is dry and goes into a wet environment, then the wood floor will adsorb moister and expand. Likewise, if the wood is too "wet" and is installed into a dry environment, it will dry and shrink.
Wood floors continuously move, just like the door jams in your home. In the summer they expand due to the increased humidity in the air and become harder to shut And, in the winter the humidity is typically lower, and the doors shrink, becoming easier to close.
Wood floors will also experience this seasonal change in dimensions. However, there are some "tricks to the trade" that will help minimize these swings.
   Use a wood that is kiln dried. This helps to ensure the wood's moisture content is the same on the inside as it is on the outside.
   A quarter-sawn wood is better than a plane-sawn wood. Plane sawn woods tend to "grow" or expand in width, while a quarter-sawn wood will tend to expand more in thickness. This helps reduce visual cracking and gapping.
   The wood should be 7% - 10% in moisture content. This may require an acclimation period in order for the wood to reach this level. Sometimes, it is best to have the radiant system installed before the wood. This will help accelerate the acclimation process.
   The wood floor should not be higher than 4% in moisture content than the floor it is being installed onto. This will allow for the subfloor and hardwood floor to move and react as a single unit. Otherwise, moisture maybe able to travel from layer to layer.

MOISTURE TESTING SLABS AND PLYWOOD SUB FLOORS   
The easiest method to test a slab for moisture is to tape a 4 ft. x 4 ft. section of polyethylene plastic sheeting to the slab and turn on the heat.  If moisture appears under the plastic, heat the slab another day and test again. Repeat this test until no moisture appears.
  If the slab is in contact with the ground and does not have a moisture barrier under it, then you will need to put a 8 mil polyethylene vapor over it before hardwood can be installed.

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