What exactly is poured in place rubber?

Poured in place rubber is a unitary surface often used in playgrounds to provide some cushioning to protect kids from falls. This system has been around for over 20 years but became popular in the last 10 years or so.

The system consists of two layers: The first layer is the base layer, or the impact attenuation layer. It is typically made out of tire buffings. Think about that extra $5 you paid per tire when you changed your car tires. The fee goes to recycle the tire. Car tires usually end up in shredded rubber nuggets that can be used as loose rubber mulch. Truck tires on the other hand can be retreaded. But for the new tread to be added, the old one is shaved down to a smooth surface. The buffings from that process is what we end up with as the cushiony part of the poured in place surface in our playgrounds. The thickness of the base layer goes hand in hand with the height of the playground equipment, and will generally be between an inch to 6 or more inches.

The wear layer is usually made up of EPDM granules (ethylene propylene diene monomer). It’s the colorful granules that sits on top of the base layer. It can also be made up of other materials, such as TPV or other polymers. But the common denominator is that it is an elastic clean rubber that acts as barrier between the kids and the base layer.

The third component of the poured in place system, and probably the most important one is the binder used to bond the rubber granules together. This is typically a polyurethane based binder, and there are two types:

1) Aromatic binder: This binder is amber in color and will change the color of the granules slightly over the years.

2) Aliphatic binder: This binder is crystal clear and won’t amber over the years but is substantially more expensive.

Both the base and wear layer are mixed with binders on site and troweled as a seamless surface. Sometimes logos and designs are embedded in the surface. The system is ideal for ADA access and inclusive play, since wheelchairs are easily maneuverable on the surface. And as a unitary surface, there is nothing to rake or top off. There is however some maintenance involved. Beside removing debris that might land on the surface, the binders holding the granules do deteriorate over time. A top coat is needed every couple years, depending on how much sun the playground gets. (See my post about poured in place repair). In another post, I will be talking about how to maintain a poured in place rubber surface.