Evaulate Fall Risks

• Safety is the biggest concern. If you build a patio on a side yard that has a steep drop-off in the back or on the sides, the patio will need railing regardless of the size of the patio, to prevent people from walking near the edge and falling off. A sloping yard next to the patio may pose no safety risk whatsoever, but a straight drop-off is a safety hazard.
  
  

Follow Building Rules

• Building codes may come into play with patios. If your local building authorities state that porches higher than 30 inches from ground level require railing, take this into full consideration. A patio constructed of stone or concrete may not be called a “porch” technically; however, if someone falls, this individual might decide to sue you. Avoid liability by installing a railing that is appropriate.
  
  

Use Appropriate Materials

• Visual appeal also a factor. Naturally, you don’t want to add colonial railings around a concrete patio made of cut stones. The materials would likely clash, but you can add metal railings that are thin and not visible from curbside. Materials -- from acrylic to rope -- are available for as outdoor railing. For example, build a couple of brick columns at the corners to match brick on the patio floor. Run a metal bar between the brick columns or install colonial railing between the two columns.
  
  

Install Perimeter Seating

• Seating can incorporate railing as a back rest. Adding a railing around the perimeter of the patio works well with perimeter benches. If a patio is especially small, and there is little or no room for larger chairs, building bench seating with back-rest railing takes up less room. Create this kind of railing similar to deck railing that slants outward. Build it of wood with two or more horizontal boards and support framing that leans outward about 30 degrees.
  
  

Leave Open Space

• Skip the railing for an "outdoor room" patio. This kind of large space usually has an outdoor fireplace. You want family and guests to walk around on one large level -- much like they were in an indoor room. Outdoor sofas, tables, overhead wooden canopies and an outdoor kitchen with stone countertops are typical. Railing will defeat the open feeling, so avoid using it if the patio is at ground level surrounded by grass.