Liquid membranes are usually polymer-based coatings that can be sprayed, troweled, or rolled onto concrete directly. They have the advantage of being quick to apply and are relatively low in cost.  Follow manufacturer's instructions on how to apply. The disadvantage of liquid membranes is that they don't offer even coverage. Even if you shoot for 60 mm of coverage, the minimum recommended thickness, it's hard to achieve that consistently. Self-adhering sheet membranes are large, rubberized asphalt membranes that you peel and place directly onto the concrete. Sheet membranes boast even thickness, but are more expensive (in both parts and labor) than liquid membranes, and can take some time getting used to.  Self-adhering sheet membranes are extremely sticky. You need to be very diligent about peeling the membrane to expose the sticky side, because it will stick to anything it comes in contact with, and it's virtually impossible to un-stick it once it is laid. Be sure to pay special attention to how sheet membranes overlap, as improper installation can result in the possibility for leakage. Make sure that lap joints are properly cut and that a bead of mastic is run down every lap joint that's spaced within one foot of a corner.  Sheet membranes need at least two people to install. Installing them by yourself is a sure recipe for a poor job and create a lot of needless frustration for yourself. EIFS offers a durable, attractive, and fairly simple coating to the outside of concrete walls, doubling as insulation and waterproofing. For a stucco-like finish, an EIFS finish coat can be applied directly to the concrete, filling any voids, floating out minor irregularities, and creating a good moisture resistant surface. EIFS are applied with a trowel, and comes in 5 gallon (18.9 L) buckets premixed and tinted to your preferred color. Float it off with a Styrofoam block or rubber float to create a uniform surface and texture.  Other EIFS products may be sprayed, brushed, or rolled on with a paint roller. Cementitious waterproofing, aside from having a moniker that takes a mouthful, are easy to mix and easy to apply. Buy them from your local masonry supply store. Mix them with an acrylic additive for a better bond, and then apply with a long-handled brush for ease. The one downside to cementitious waterproofing is that it doesn't have any elasticity, making it prone to cracking over longer periods of time. Sodium bentonite is used in a lot of city dumps to prevent liquids from leeching into the underlying soil. It is essentially clay, and will act as a good waterproofing agent if you're concerned about leaving a human footprint. Bentonite also has the advantage of being able to cover smooth as well as coarser surfaces.
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One-sentence summary -- Use a liquid membrane for quickness and economy. Use a self-adhering sheet membrane for consistency. Try out EIFS, or exterior insulated finish systems. Try using cementitious waterproofing. Opt for sodium bentonite if you want to use a non-polluting, "green" method of waterproofing.


You will definitely need a permit or a license to open your business.  However, the requirements will differ depending on what state you live in.  The SBA website maintains a list of business license offices to help you find the information. In addition to a business license, you will need a federal tax identification number and possibly a sales tax license, income tax withholding, and unemployment insurance tax.  Ask your state business office about the insurance requirements for your car wash business. Once you get all of the necessary permits and licenses, keep track of your renewal dates and make a copy for your business records.  You will also need to display your license in your car wash so that customers can see it. The equipment you buy will depend on the type of car wash you have decided to open and the services you offer.  Full service car wash, self-service car wash, and an automated car wash will all have different needs.  You will typically need to buy a washing system (e.g. pressure washer, conveyor, self-service equipment, mobile wash systems), chemicals (e.g. cleaning solutions, wax, spot free rinses, protectants, presoaks, etc.), dryers, blowers, vacuums, brushes, towels, compressors, pumps, and a water system (e.g. boilers, water heater, water filtration, extractor, etc.), and billing system.  If you buy the cheapest version of everything, you might be able to get started for about $2000. If you want a nicer setup, it will probably run you about $5000 or more.  The International Carwash Association has a supplier guide to help you find reputable manufacturers.  Look in trade magazines like Auto Laundry News and Modern Car Care to buy your chemicals.  It is best to buy from big manufacturers.  Make sure the distributor of your equipment is available to service your equipment when needed. Find out how they handle equipment servicing before you buy from them. Use a multifaceted approach to advertise your business that includes flyers, posters, and an online presence. The signage for your car wash should be colorful with clear messaging.  Make sure that people can easily see it from the road.  A popular way to get new customers is by distributing coupons or discounts for car washes. Also, develop relationships with other small businesses located near your car wash.  Social media is an important aspect of marketing these days. Set up a website and establish a presence on Twitter and Facebook.  Make sure any of the paper items that you have include links to your website and social media accounts. Use your website to share information about taking care of your car and other relevant tips. Schedule a visit to your local radio station to discuss your new business. Consider starting a loyalty program. This will encourage repeat customers instead of people who use the coupon one time and never return. A car wash business is very customer-focused.  Your employees should be punctual, efficient, skilled, and have excellent communication skills. As you conduct interviews, pay attention to body language and communication skills to get an idea of how the person will interact with customers and coworkers. Always check the references of potential employees as well. Have a soft opening of your car wash before you have a big grand opening.  Wait at least 30 days before you have the big event. You want to work out some of the kinks and feel comfortable with the car wash before you make a big deal. Think of a grand opening as a party and social event to generate publicity.  Invite friends, neighboring businesses, your supplies, and the media Give away free car washes and promotional items.
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One-sentence summary --
Get the necessary permits and licenses. Buy equipment. Market your business. Hire employees. Open your car wash.