Whenever you set up, it is a good idea to place a pad of some sort between your leveling jacks and the ground. This distributes the weight of your coach over a larger area. In the case of macadam (black top) and grass, reasonably sized jack pads can help prevent sinking. In the case of concrete, it can help protect it from cracking under the direct pressure. There are many different options when it comes to jack pads from store bought to home made.
Jack Pad Sizing
Believe it or not, there is actually a formula that can be used to determine the proper size of jack pad to use for the weight of the vehicle. Unfortunately, I’m writing this article long after I had already built my jack pads and have lost the reference to math. What I discovered though was that I should have had a 20″ or greater pad for my 28,000lb motorhome. This seemed overkill to me so I stuck with 16″ since I was using a piece of 4×8 pressure treated plywood (but more on that later). The basic principle is this; the larger the pad, the lower the PSI on the ground surface below. When I used to work in the furniture industry we would set up water beds on Styrofoam cups to demonstrate the load distribution.
Plastic Jack Pads
As with anything, there will be a trade off when you compare store bought to home made jack pads. The most common store bought pads are the plastic blocks that usually come in a pack of 10. These are great for trailer leveling as they can be oriented into a ramp to make it easy to back up on to. There are numerous stories of the plastic pads breaking under the direct pressure from the jacks of a heavy motorhome.
Rubber Jack Pads
Another option are the rubber jack pads. These are high density rubber blocks usually about 3/4″ or thicker. These typically won’t break down and are well suited for concrete environments. They’re not well suited for softer grounds such as grass or macadam because the rubber is flexible.
Wooden Jack Pads
Properly built wooden jack pads will stand up to all environments but the trade off is the added weight to carry around. These types of pads will be built from pressure treated 2×12 or plywood. The key to wooden jack pads is to make sure that the grain direction are alternated to help prevent warping.
What I built…
As you’ve already guessed, I built wooden pads. I’ve actually built two different sets one small from 4×6 and one large from plywood. Today I use the large ones while camping and use both together to ground the coach in storage without putting the jacks down. This takes the load off of the tires and keeps the jacks up to prevent pitting. Since my coach has air bags, I stack the blocks under the jack and release the air letting the coach settle onto the pads. I also put a piece of horse stall mat on the bottom of each pad. It adds a little more protection for concrete surfaces and adds a little bit of insulation for lightning protection. It probably won’t help during a direct ground strike in close proximity to the coach but it also won’t hurt.
Built from pressure treated 2×12 lumber. I cut them into squares so they’re actually 11 1/2″. The two pieces are glued together using construction adhesive and then screwed using deck screws. I used a piece of horse stall mat to make a rubber bottom which was glued to the wood using contact cement. Adding a handle and some rope made them easy to maneuver and pull out from under the coach.
Built from pressure treated 3/4″ plywood cut into 16″ squares. They’re actually 15 1/2″ due to the way lumber is measured. There are 4 pieces per pad. Each layer is glued with construction adhesive and screwed with deck screws. While probably overkill, I wanted to make sure that these pads wouldn’t warp. I glued a piece of horse stall mat to the bottom using contact cement. Add a handle and piece of rope and these pads are good to go.