There's a wide range of moisture barrier products on the market and various installation techniques.

Because moisture control is so crucial to the success of the overall floor covering project, you should always follow the manufacturer's instructions closely.

This includes using any other products specified by the manufacturer if it forms part of an overall 'moisture barrier system', to ensure that all the products you're using are compatible and that you've satisfied their warranty conditions.

Remember, incompatible solvent-based adhesives can react with some moisture barrier products and cause costly failures.

Even if you've put a cement-based compound in between the adhesive and the moisture barrier, you may still not stop the solvent from penetrating.

Below are the general principles involved in installing a two-part epoxy resin moisture barrier.

Preparation and installation procedure

1. Remove all surface contaminants and weak or powdery material from the concrete substrate.
   
   This can be done by shot blasting, scarifying or diamond grinding.
   
   The final surface must be clean, porous, bare concrete.

2. Remove all dust and debris.
   
   Allow the floor to stand for at least 30 hours to let any moisture from the shot blasting or grinding process dry out.

3. Note any cracks in the substrate for future reference. Check all expansion joints and construction joints and repair them as required.
   
   
4. Give the floor a final vacuum to remove any remaining dust.
   
   

5. Apply a primer to the surfaces.
   
   This will improve the bond strength of the moisture membrane, particularly on fibre cement wall sheeting that has been sanded but is still holding a fine dust from the hard-set plaster.

6. Cover all joints, waste junctions and other penetrations with woven fabric tape, or other bond breaker materials, as specified by the manufacturer.
   
   In some cases, a silicone or polyurethane sealant may be recommended by the manufacturer.

7. Mix the epoxy and hardener components together. Apply the mixture to the floor with a notched trowel, squeegee or brush.
   
   Make sure that the correct thickness is maintained by using the specified amount for the area to be covered.
   
   Continue the barrier up the base of the walls to at least 150 mm above floor height.

8. Use a nap roller to roll out the product, making sure there are no pinholes or bubbles in the coating.
   
   
9. Wait for the specified amount of time, and then apply a second coat at 90 degrees to the first coat.
   
   Again, check that the correct thickness is maintained by using the quantity specified for the second coat.

Cracks and expansion joints

Non-active cracks should be filled using the method recommended by the product manufacturer.

One method is to 'V' gouge the crack, prime it with epoxy resin and then fill it with a slurry of epoxy resin and Portland cement.

Active cracks - that is, cracks that could move over time and either open or close - should be noted and discussed with your supervisor to find out whether a structural engineer's advice is needed.

These sorts of cracks can result in later moisture problems and show through a finished resilient floor, so they may require specialist treatment.

Expansion joints must be continued right through the moisture membrane and underlayment. One method of keeping them open is as follows:

• put a backer rod in the joint and mark its position on the walls or other fixtures at each end
  
  
• coat over the top of the joint with the moisture barrier and underlayment
  
  
• put two vertical saw cuts through the underlayment to expose the joint
  
  
• remove the material and coat the sides of the saw cut with moisture barrier
  
  
• install a jointing system recommended by the manufacturer.