We’ve touched briefly on the concept of Hollow versus Solid wrought iron balusters (aka metal spindles), but we decided you may like more information on the pros and cons of purchasing and installing hollow or solid metal spindles.  Iron balusters come in many shapes and many of these are available in two categories; yep you guessed it, solid or hollow.  So what exactly is the difference between the two, other than the obvious?  Following is a comparison of those characteristics that you should consider when making your decision between the two variations of iron balusters.

Strength & Durability

Solid Iron Balusters are made from a low-grade iron called “wrought iron”.  Even though the iron is a low grade because they are solid iron they are very strong and durable.
Hollow Iron Balusters are made of a higher quality iron which makes them comparably strong to the solid version though they do seem to have a little more deflection or flex.  Still, they are completely adequate and meet stair code compliance.
Conclusion:  If it is critical that your stair railing system is “solid” or has very little flex, Solid Balusters are the way to go.  However, an exaggerated example may help you understand why a baluster can be both strong and flex at the same time.  Think of a trampoline, very strong but lots and lots of “flex”.  Hollow Balusters have just slightly more flex than Solid Balusters.

Cost
Solid Iron Balusters require more steel, are heavier and can be more expensive, especially when considering shipping.
Hollow Iron Balusters are often less expensive because they require less material and weight less than the solid option.
Conclusion:  Hollow metal spindles usually translates to less expensive but make sure to compare pricing to verify this.  Also, Hollow Iron Balusters are more environmentally friendly; less material and reduced fuel required to ship because of their lower weight.

Installation

Solid Balusters are harder to cut for installation.
Hollow Iron Balusters are easily cut by hand with a hack-saw or a grinder with a metal cutting wheel.
Conclusion:  If you are concerned about cutting, hollow metal spindles are definitely easier, although it just takes more effort to use the same tools to cut solid.

Versatility

Solid Iron Balusters are suitable for both interior and exterior use.
Hollow Balusters are not generally considered suitable for exterior use unless they are welded to the metal top and bottom rails.  This is because without a welded “seal” moisture can accumulate inside the baluster and cause them to rust from the inside out.
Conclusion: If you are using iron balusters on an exterior railing system with non-metal or non-welded top and bottom rails then we recommend you use solid metal spindles.

Design Possibilities

Solid Iron Balusters are available in a greater variation of designs.
Hollow Iron Balusters are more limited in their variations so they do not yield as many pattern options.
Conclusion:  If everything else has been considered and there are hollow baluster designs available to create the pattern you want, go for it.

Surface Texture

Solid Iron Balusters have a more rough or textured surface which can be a pro or a con depending on your desired look.
Hollow Iron Balusters have a very smooth surface.
Conclusion:  Do you like a more old world forged texture or completely smooth?  Also, you should consider the fact that some powder coat colors are slightly textured and will conceal any difference between solid and hollow iron balusters.

Similarities

Both Solid and Hollow metal spindles have a  dowel top for easy installation into wood stair handrails.  They are both available in a variety of powder-coated colors and there are a wide range of iron baluster accessories which are almost completely interchangeable.

As you can see the choice between solid and hollow wrought iron balusters is often a subtle one.  This is not like comparing solid hardwood to veneered plywood which basically comes down to the quality of solid versus the price of veneer.  In the case of iron spindles, both are completely adequate for interior balustrades and the decision is up to you based on your situation.  Hopefully, this helps you analyze this question with a little more knowledge.