"Water and de-icing salts are prime movers in causing corrosion in embedded steel reinforcement, yet hand washing of cars is becoming an increasingly common practice in car parks. The practice can cause damaging de-icing salts (introduced from the roads via the cars) and excessive water to be deposited onto the concrete decking", he explained. "In winter, salts are washed off the vehicles and in the summer, the water supports a high corrosion rate" he commented. "In addition the chemicals used to clean the cars may also be found to be detrimental to the structure."

"Whilst car park owners probably view vehicle washing as both a service to their customers and a revenue generating operation, such benefits are likely to be far outweighed by increases in long term maintenance costs", he warned.

Mr. Drewett also pointed out that new clients often fail to provide the correct brief to their designers and as a result many new structures are being built without adequate drainage and deck waterproofing systems to accommodate car washing activities. There are still plenty of instances, he said, where car parks are being built without the installation of a deck waterproofing membrane. He predicted that such structures could be hit by "extensive chloride contamination" within as little as ten years.