Every shed we construct is custom to the clients needs, therefore the best way to answer this question is to get a quote for the structure you wish to build.
Below we will give you general estimates on what it costs to build a car wash or truck wash, based on jobs we have done in the past.
Small to Medium Car or Truck Wash

This range generally includes small truck wash bays, and covers any job between $15,000 and $30,000.
Medium Car or Truck Wash 
This bracket covers projects between $30,000 and $40,000.
Large Car or Truck Wash

Large scale projects of this type usually range between $40,000 and $55,000.