Multi-storey car parks suffer from major reinforcement corrosion problems due to chlorides from de-icing salts.

To prevent chloride ingress, deck membranes can be used on new and existing car park decks and where chlorides are already present they will also help to reduce the moisture content of the concrete and suppresses the corrosion activity.

It is important to note, however, that deck membranes will not by themselves stop the reinforcement corrosion and additional corrosion control techniques, such as cathodic protection, will be required for long term durability.

Most car park owners and operators use surface membranes that, in addition to providing good protection, also improve the aesthetics of the structure. An extensive range of proprietary materials, based upon epoxy, polyurethane and methacrylate are available, but each has its advantages and disadvantages.

Deck membranes can also be clear impregnation treatments such as silane, which is hydrophobic. Silane lines the surface pores of the concrete, prevents water ingress, but does not change the substrate’s appearance. Some suppliers manufacture combined silane and corrosion inhibitor materials.

Because of the large choice, therefore, selection is not an easy task and the following main factors need to be taken into consideration:

• Past Projects
  
• BBA Certification
  
• Material costs
  
• Technical understanding and support
  
• Contractor training and approval scheme
  
• Quality contractors
  
• Warranties
  
• Curing time
  
• Crack bridging properties
  
• Flexibility
  
• Slip resistance
  
• Colour schemes
  
• Ease of use
  
• Environmental
  
• Future maintenance requirements
  
• Durability
  
• Quality control procedures
  
• Client references

It is important to base selection on performance as well as cost, since low cost thin membrane systems can fail early.

Usually the exposed top deck will be treated with a flexible waterproof membrane able to accommodate thermal movement. Lower decks usually receive what is termed ‘interdeck membranes’. The ramps and turning circles may require thicker membranes to accommodate additional physical wear. Some membrane systems are sensitive to weather conditions and over coating times can be critical.

Overlaying old thin membrane systems, or asphalt, presents a much more likely risk of failure. There are a few deck membrane systems that are suitable for application to asphalt, but in most circumstances the thin membranes should be removed before the new membrane is applied.

The quality of the installation contractor is critical to the long term performance of the membrane. Surface preparation by planning, vonarx machine or blast tracking is important. The contractor should be fully qualified and approved for the selected material.

Concrete Repairs Ltd (CRL) is an approved applicator for all the leading material suppliers. CRL is also able to provide independent advice on the material selection, based on many years of experience. Sample applications can be provided to further assess the performance and appearance of the systems.