Answering questions about “do I need a special foundation” is difficult and there are many considerations like thickness and quality of your current foundation, the soil under the foundation, and the size of the hammer.
I can share my own personal experiences and those of many Anyang users:
1. 95% of my customers that own an 88lb or smaller hammer use their existing foundation with no modification. I recommend filling the base with sand and placing a ¾” piece of plywood between the concrete and the hammer base and then anchor the hammer to the concrete. This works just fine on most healthy 4” to 6” foundations. I’ve had my 88lb on my 6” pad since 2004 with no signs of a foundation issue. Worst case, if you find that you are getting more vibration that you want, it is easy to remove the hammer and install an isolated foundation.
2. For the larger hammers, 120 lb. and up, I highly recommend pouring a separate foundation. I’ve had a few customers that were renting a shop and ended up simply bolting the 165 lb. to the foundation. It did work and no damage to the floor has been reported but its not good practice.
3. For a disclaimer, I am not a structural or foundation engineer. If you are concerned about your specific soil conditions or application, I would suggest consulting a professional engineer. I will describe what I did for my foundations and what worked for me. If you decide to install a separate foundation, it is not that difficult and can be done for $400 to $700. I have built two isolated foundations in my shop, for the 165 lb. and the 242 lb. hammer. I rented a concrete saw to cut out the new foundation perimeter and then a jack hammer to remove the concrete. Then I dug a hole 4’ deep (concrete is cheap), built a rebar cage that I could set in the hole. I also used 1” Styrofoam insulation to isolate the old foundation from the new concrete pour. I also welded threaded rod to the rebar to anchor the hammer and poured the concrete. After the concrete set, I chipped out about 1" of the Styrofoam and used a rubberized caulk in the seam between the old foundation and the new one. It was a several day job but there is absolutely zero vibration (that I can detect) in the old foundation. There are also many articles on the internet for further research.