There are three principal layers; 1  External intercostal muscles aid in quiet and forced inhalation. They originate on ribs 1-11 and have their insertion on ribs 2-12. 2  Internal intercostal muscles aid in forced expiration (quiet expiration is a passive process).
Costs. A professional concrete contractor will typically charge $2-$4 per square foot for a simple stain application, including the sealer. A stain application with patterning and sawed lines will typically cost between $4 and $10 per square foot.
How to Stain a Concrete Walkway. Staining a concrete walkway is a low cost option for adding significant curb appeal. With a few simple tools, you can stain your walkway for as little as 50 cents per square foot. The most important thing to remember is, once the process has begun you cannot stop.