A porch ramp is not a weekend shelf. It is a short piece of structure that has to meet the ground, the door, and a load it may never have carried before. Taking it in stages keeps each decision honest and shows you where to stop and call someone.
Local option: New Plan Care gives families in the St. Louis area in-home help so a parent can stay home: companionship, help with bathing and dressing, meals, and overnight care. Call (314) 405-0887.
Start at the door
Stand at the threshold where the ramp will land and measure the height from the finished landing surface down to the ground at the foot of the run. That number is the rise. Write it on paper and keep it, because every later choice depends on it.
Then decide where the ramp will sit. Look for a path that does not block a step route, the trash can path, the car door, or the place a helper parks. Walk the path yourself. If the ramp will not fit on one side, sketch the other side before you buy any lumber.
Set the run and the slope
Divide the rise by the slope you are allowed. Many home guides use about one inch of rise for every foot of run, and many local codes and ramp kits ask for something gentler. Check your city's building office and the manufacturer's manual for the number that applies to you, and use the longer run if the two disagree. A ramp that is too steep is the one that gets used least.
Ask the building office whether a permit is needed. Some cities require one for a permanent ramp and not for a portable one. The permit question belongs at this stage, not after the concrete has set.
Set the footings and the landing
A permanent ramp needs footings that sit below the frost depth for your area and will not heave when the ground freezes. Dig to the depth your local code gives, set the forms level, and let the concrete cure before you load it. Do not set a ramp on loose pavers or loose soil and call it finished.
The landing at the door should be level and large enough for the door to open fully and for a person to stand, turn, and reach the handle. Check the joint where the ramp meets the threshold. If the ramp leaves a step or a lip there, the job is not finished.
Surface, edges, and rails
Choose a surface that gives grip when wet and does not hold standing water. Add a rail on any side that drops off, and test the height and grip of the rail with your hand, not a tape. Fix the rail brackets into solid framing, not only into the decking.
Test the ramp before anyone relies on it
Walk the ramp empty, then with a helper, then with the heaviest load it will carry in daily use. Watch for flex, gaps at seams, pooling water, and any board that moves under your feet. Check the joints again after the first wet week and after the first cold snap. Write down what you found and who will fix it.
When any part of the build touches the structure of the house or needs digging near utility lines, stop and call a licensed person. If you need help finding one, the local help page is a place to start.