Absolutely, you can add armrests to a standard park bench after you buy it—but the ease and approach depend on the bench's design and materials. Many modern park benches come with pre-drilled holes or mounting brackets that allow you to attach armrests as an optional add-on later, so check with the manufacturer first. If your bench lacks those provisions, don't worry: you still have options.
One common solution is to purchase universal retrofit armrest kits designed for benches. These typically clamp onto the slats or frame using bolts and brackets, requiring no permanent modification. For wooden benches, you can also fabricate custom armrests from treated lumber or metal and secure them with carriage bolts. For metal benches, welding is an option if you have the tools or can hire a professional.
However, there are a few caveats. Adding armrests later might void the warranty, and you'll need to ensure the armrests are sturdy enough to handle weight and weather exposure. Also, consider the bench's intended use—in public spaces, retrofitted armrests must meet safety and accessibility standards.
In short, while it's easier to order armrests together with the bench, retrofitting is definitely possible with a little DIY effort or professional help. Always measure your bench carefully and choose armrests that match the style and material for a seamless look.