ar ▁layer ", ▁is ▁typically ▁ <0xE2> <0x85> <0x9C> ▁inches ▁thick ▁and ▁made ▁of ▁EP DM ▁or ▁T P V ▁gran ules . ▁The ▁second ▁layer , ▁or ▁" c ush ion ▁layer ", ▁is ▁ 1 – 5 ▁inches ▁thick ▁and ▁made ▁of ▁cr umb ▁rub ber ▁or ▁rec yc led ▁rub ber ▁t ires . ▁The ▁surface ' s ▁thick ness ▁depends ▁upon ▁usage ▁and ▁play ▁equipment ▁with ▁ 1 5 – 2 0 ▁mm ▁for ▁hard ▁surfaces ▁and ▁ 4 0 ▁mm ▁for ▁com pressed ▁stone . ▁The ▁raw ▁rub ber ▁particles ▁are ▁bound ▁together ▁with ▁a ▁poly ure th ane ▁b inder ▁and ▁mixed ▁or ▁made ▁on - site . ▁The ▁surface ▁comes ▁in ▁a ▁wide ▁range ▁of ▁colors ▁and ▁even ▁mi xt ures ▁of ▁colors . ▁A ▁typical ▁pou red ▁rub ber ▁surface ▁meets ▁national ▁standards ▁for ▁safety ▁and ▁A DA ▁wheel ch air ▁access ibility . ▁ATP ▁rub ber ized ▁unit ary ▁surface : ▁ATP ▁stands ▁for ▁ali ph atic ▁therm op last ic ▁mon omer . ▁This ▁surface ▁also ▁meets ▁safety ▁and ▁access ibility ▁standards . ▁It ▁consists ▁of ▁a ▁layer ▁of ▁almost - s pher ical ▁rub ber ▁particles , ▁about ▁one - six teenth ▁of ▁an ▁in ch ▁in ▁diameter , ▁which ▁are ▁chem ically ▁bound ▁by ▁a ▁color - fast ▁b inder . ▁This ▁surface , ▁in ▁turn , ▁is ▁bond ed ▁to ▁a ▁layer ▁of ▁engine ered ▁rec yc led ▁fo am ▁( ER F ) ▁to ▁abs orb ▁shock . ▁The