Building a concrete ramp can help make many places around the home safely accessible to those in a wheelchair or with limited mobility. Anyone with basic carpentry skills can build a concrete ramp. A ramp is typically defined as any paved walking surface that has a slope of more than 1:20 (1 unit of vertical rise for every 20 units of horizontal travel). When a paved surface exceeds this slope, walking on it can be difficult or even dangerous if a few important design considerations are not followed. To begin with, handrails should be provided on both sides of any ramp. In addition, the surface of a ramp should be somewhat rough to provide traction; otherwise, somebody could slip and fall--especially if it rains and the surface becomes wet. The following steps will guide you through the process of constructing a well-built concrete ramp with handrails and a roughened walking surface.
Determine the best location for your ramp. The ramp should have a flat area (landing) about 5-feet long at the top of the ramp and a landing about 6-feet long at the bottom. Your ramp should be at least 42-inches wide, so make sure you have a clear area about 6-feet wide to work in. Use a pencil to mark the locations on the upper and lower landings where the ramp will meet the landings.
Use spray paint to draw a line on the dirt between the marks you have made on the landings. These lines will represent the sides of your ramp.
Use a square-edge digging shovel to excavate the top layer of dirt in the area bounded by the landings and the painted lines (the footprint area of the ramp) so that you have about 7 inches between the top of the ramp landings and the bottom of your excavation. You are digging out the soil for two reasons: first to remove loose matter and debris from the area, and second to remove enough material to allow room to eventually place the desired thickness of concrete.
Use the shovel to dig a shovel-width trench along each side of the ramp. The trenches should run along the entire length of the ramp. Try to visualise these trenches as continuous footings along each side of the ramp that will be filled with concrete. These “footings” will help to lock the ramp into the soil and will support the handrails. Dig these footing trenches so that they will be about 12-inches-deep, measured from the top of the ramp to the bottom of the trench.
Once the digging is complete, you will be ready to place some formwork. Since, for this ramp, you are constructing a ramp between two existing landings, you will only need formwork for the sides. Cut to length and place a piece of 2-by-8 stud lumber on each side of the ramp excavation (the 8 inches side of the stud should be vertical). You will have to trim each end at an angle to fully mate with the upper and lower landings. Align the inside face of each stud with the outside edge of the footing trenches. These 2-by-8s will be sloping, as they are connecting the pencil marks you have made on the upper and lower landings. The 2-by-8s will serve as formwork for the sides of the ramp and also as guides for screeding the concrete (explained later in the process).
“How do I support the 2-by-8 formwork in place?” you may ask. Now that you have the formwork cut to length and you have an idea of where to place them, drive stakes into the ground just outside the edges of the ramp so they can support the formwork. Don’t worry about how high the stakes are at first–just make sure they are driven firmly into the soil and are at least tall enough to intersect the 2-by-8 formwork. Temporarily clamp the stakes to the 2-by-8s, adjust for final position, and secure with two No. 8 woodscrews at each stake location. Stakes should be spaced no more than 3 feet apart. Once the stakes are in and fastened to the formwork, trim the stakes so that they do not protrude past the top of the formwork.
Cut 9-inch-long segments of 3-inch diameter pipe. The amount of segments you cut will depend on the length of your ramp. You will need one for every vertical rail support. These segments will serve as “sleeves” that will be embedded in the concrete and will accept the handrails after the concrete ramp has been poured. You should place a sleeve at each corner of the ramp and equally space sleeves along the sides of the ramp so that they are no more than 3 feet apart. The top of the sleeves should be about 3 inches away from the 2-by-8 formwork (centred on the width of the trench footings) and just below the top of the formwork. You can hand-mix some concrete and place a dollop under each sleeve location to support the sleeves in place. The bottom of the sleeves should be kept at least 3 inches away from the bottom of the trench footings. Tape the tops of the sleeves with duct tape so that no concrete can enter into them later when you pour the concrete for the ramp.
Lay a 3-inch bed of ¾-inch gravel down on the bottom of the ramp excavation. Tamp firm with shovel.
Cut a piece of welded wire mesh fabric that is 6 inches shorter than the width and length of the ramp. Place it on top of the gravel, centring it on your ramp. There should be a 3-inch gap all around the mesh fabric between it and the ramp sides.
Mix and pour concrete into the ramp area. Rap on the 2-by-8 formwork as you are pouring in the concrete to help the concrete consolidate and form a solid monolithic mass. Tapping the formwork with a hammer or otherwise vibrating the concrete as it is poured helps it flow better against the formwork and will guard against voids forming in the final product. At the same time, reach down and grab the wire mesh fabric at various locations and tug it upwards so that it rests roughly mid-depth in the concrete.
Use a 2-by-4 to level (“screed”) the top of the concrete. Use the 2-by-8 formwork on the sides as support for your 2-by-4 and pull it back and forth and up and down along the length of the ramp. Fill in voids until the top of the concrete is flat, uniform and flush with the tops of the 2-by-8 formwork.
After waiting until water no longer pools on top of the concrete and it begins to stiffen up a bit, gently drag a wide stiff bristle broom across the ramp along its entire length. You’ll have to experiment on a small area to check for proper stiffness of the concrete. You should barely notice the locations of your sleeves at this point. Don’t worry about covering them up with concrete. These will be easy to uncover later on.
Allow the concrete to set and cure after finishing with the broom texture is complete. Cover the ramp entirely with plastic sheeting to slow down the evaporation of moisture in the concrete. This process is referred to as “curing.” By this time, laying down a plastic sheet should not deform the concrete surface. If it does, remove the plastic and wait until the surface stiffens before placing the sheeting again. Ideally, the concrete should cure for about a week with the sheeting in place, but continuing to the next step to install handrails could begin the next day, as long as the sheeting is kept in place. Spraying the curing concrete with water every four hours will also aid in the curing process.
Create railings from 1 ½-inch threaded and galvanised steel pipe. Use threaded T-fittings and elbows to mate vertical segments to the horizontal rail segments. The number of vertical segments will vary with the length of your ramp. Vertical segments should not be spaced more than 3 feet apart. Use vertical segments that are roughly 44 inches long so that about 8 inches can be embedded in the pipe sleeves leaving the horizontal rail segments about 36 inches above the concrete ramp surface.
Place handrails on both sides of the ramp by setting them into the pipe sleeves that you placed in Step 7. Use a utility knife to cut and remove the thin layer of concrete and duct tape at the top of each sleeve. Use mortar repair grout to fill the void and set the rails into the pipe sleeves
After the concrete has had about a week to cure, remove the plastic sheeting and clean your new ramp surface with a garden hose.
Before beginning, make sure that the slope of your ramp does not exceed 1:12. If it does, reconsider the placement of the ramp so that it can be longer, resulting in a shallower slope. Ramps that exceed a slope of 1:12 are considered too steep by most building code officials.
Always wear proper safety attire when working with power tools. Avoid skin irritations by wearing heavy-duty rubber gloves and safety glasses when working with concrete.