The first thing you have to do is determine the slope of the ramp. If possible, try to keep the slope around 11 or 12 degrees. This translates to about 2 inches of rise for every 12 inches of run. Steep ramps can be dangerous when wet, and they can be very problematic for lawn mowers that have low-hanging belly mowers.
If the ramp is too steep where it connects to the flat floor of your shed, you can have the bottom of the belly mower scrape at the pivot point. I’ve seen mowers get stuck because the rear drive wheels of the garden tractor lift up and lose traction.
You’ll probably end up using a measuring tape, circular saw, hammer, drill, framing square, spade, level and a few miscellaneous tools. Most of these are common or can be borrowed from friends if necessary.
I prefer to use all treated lumber for the outdoor ramps I build. I frequently use 4-by-4-inch timbers for the ramp supports and then cover this with treated three-quarter-inch plywood. You can buy plywood that has the same chemicals as treated framing lumber. It can last for years and years getting wet without rotting.
What’s critical is how you attach the ramp to the shed. You don’t want the ramp to crash to the ground one day while you’re walking on it or while the garden tractor is on the inclined plane.
What has worked well for me is to engineer the ramp so the plywood overlaps the framing lumber at the doorway to the shed. I try to make this overlap at least four inches. This often means you have to nail additional framing lumber to the inside face of the outer floor joist of the shed. The outer floor joist of the shed and the added framing lumber have to be cut away to have the same slope as the ramp will have.
Taking the time to make this connection allows the plywood for the ramp help hold the ramp supports close to the shed. For the shed to fall away, the plywood would have to rip away from the shed joists. That would be very difficult if you use stainless steel fasteners or galvanized ones that won’t rust.
I often attach a simple treated 2-by-4 to the face of the outer shed floor joist. This acts like a tiny beam to support the ends of the 4-by-4s that make up the supports for the ramp. I notch the bottoms of the 4-by-4s so they sit flat on the 2-by-4 ledge. The top of each 4-by-4 is flush with the beveled floor joist of the shed. This allows the ramp to be smooth and in the same plane.
I space the 4-by-4s two feet on center. This provides plenty of support for the thick three-quarter-inch plywood. Where the 4-by-4s touch the ground, I usually put an additional 4-by-4 under them. This 4-by-4 runs perpendicular to the ends of the ramp 4-by-4s. It acts as a beam to support the ramp timbers and helps keep the ends all in the same plane.
The 4-by-4 that supports the ends of the ramp timbers needs to be placed below grade so that the end of the ramp ends up touching the ground. You don’t want a big dropoff at the end of the ramp. It needs to transition smoothly to the ground.
Most of the ramps I’ve built are no more than eight feet long. If you have to build a longer ramp, you will probably have to add support under the ramp 4-by-4s, as they’ll get a little spongy. You can do this with concrete blocks, rocks or other masonry materials that you place on the ground under each 4-by-4 ramp timber. You want the ramp to be solid, not like a trampoline.
Tim Carter is a columnist for Tribune Media Services. He can be contacted through his Web site at www.askthe