A lot of people who have never handled steel cable before do not have an idea on what size and type of cable to use for a cable railing system. A lot of different styles and grades of cable can be used, but only a few types end up with the best results over time.
Residential projects typically use 1/8” cable. This cable is the smallest you can go while still passing building code, so most people decide to use it on their homes. The 1/8” is less visible to the naked eye while being safe for children and pets. It is also the most economical.
If a homeowner would like something that is more visible from a distance, using a thicker cable like the 3/16” would be best. A lot of times the homeowner or designer would like to feature the marine style of the cables and would like the overall aesthetic to be more prominent. 3/16” is perfect for these situations. The 3/16” cable is also typically used in commercial applications
1/4” cable is recommended for industrial applications. The 1/4” cable is typically not recommended for residential projects because it is harder to work with compared to the smaller two sizes. Plus, there are a limited number of options in terms of fittings in the thicker size.
Strand of Cable:
There are different strands of steel cable wire rope which explains how the cable itself is braided together. For cable railings, some strands are good and some are ones to be avoided.
The universally recommended type of strand of cable to use for a cable railing is the 1×19. This means there is one group of 19 strands braided together to form the cable. Because there is only one group of strands, this type of cable is very stiff. This stiffness helps because the cable does not require as much tensioning and also helps maintain the tension over time. The 1/8” 1×19 can go around bends, but the 3/16” and ¼” 1×19 are extremely stiff and do not bend well.
Another type of cable that could be used for a cable railing would be the 7×7 strand. This is a medium stiff/medium flexible cable. This strand is better for going around corners and bends as there are more small strands in it.
A popular cable that should be avoided for cable railings is the 7×19. Seven groups of 19 strands braided together forms a very flexible cable, which is the opposite of what is desired for a railing. This type of cable is typically used on pulleys and winches where the flexibility is important.
Grade of Cable:
There are several types of grades to select from in terms of steel cable wire rope. The lowest grade is a galvanized, which is not recommended for architectural railings as they will corrode quickly. A middle grade of stainless steel, which is typically used for indoor applications, would be the T304 stainless. The top grade of stainless steel cable is the T316, which is also referred to as “marine grade.” This type of cable is always recommended for any railings you would like to look good for a long period of time with minimal maintenance. A lot of natural elements can break down cable over time. Natural occurring salts, acid in the rain, saltwater spray, etc. will all corrode any type of steel cable, but the T316 is the best in terms of longevity.
A lot of people inquire about a PVC coated cable for a cable railing. Hypothetically, this sounds like a good idea as the PVC provides a protection from the harsh elements as well as the small steel strands of the cable. In reality, this is a very bad type of cable to use for a railing as the PVC ends up turning brown being exposed to sunlight and weather. Plus, the PVC typically covers a galvanized cable, which will end up corroding on the ends anyways, causing visual structural issues as well. Bare, stainless steel cable is the best way to go.