Got to make a ramp, A is decking and lets say its 18" tall. B is the ground and C the straps to attach the ramp decking boards to.
How do i work out the angles at each end? At A its Fairley easy but at ground level. Do i just cut a level line back from the widest point to the right what makes sense in my head but would this not make the decking end A out of sync?
Think of it as 2 right angled triangles one inside the other, the difference being the thickness of the sloped board. You know the height A and the distance B you need so good ol' Pythagoras will give you C (A² + B² = C²)
If it's angles you need then you're into sine, cosine and tangents. Hypotenuse/opposite = sin, opposite/adjacent = tan and hypotenuse/adjacent = cos (HAC, HOS, OAT) and you'll know opposite and adjacent lengths.
Worth noting that the way you've drawn it, C isn't long enough.
When you make the angled cut at A it will move left, so not reach as far to the right.
Then when you cut the right hand end, it will drop lower, so there will be a gap at the top of A because the angle will be wrong.
Redraw the diagram with a single line between the two furthest apart contact points.
Then draw another below it, the width of the slope, overlapping the vertical and horizontal. That will give you the two angles.
Thoughts:
1. Right hand end. No point trying to cut to a fine point if it's likely to rot over time
2. If a long slope, it will need supporting.
3. What's it for? Anything other than a very shallow slope will be difficult to walk on, especially when wet. Consider using deck boards with built-in 'grippy' stuff (they're more expensive).
4. How will you fix it in place and support the ends? A horizontal at A? If so, that might need chamfering too.
Remember, it’s decking not cabinet making. Even the best angle/mitre will move after a few months of rain and heat.
You’re going to have to put something under AC to support it and also some non slip stuff which you can get a stickyback version by the roll from Amazon (I had to make a similar ramp onto the decking for our dachshund).
You're essentially making the same calculations as roofers do when building a pitched roof frame. There are loads of roof calculators online, or better yet get yourself a speed square - the Swanson one is one of the best.
I am thinking cut up the green dotted line above the A then measure its highest point. If it is say 6.5cm then cut the other end at 6.5cm along that dotted line. Then fingers crossed it falls into place.
The ground is a concrete footpath and probably put down by the council (corporation) back in the late 50's so never going to be flat. This is for a guy in a wheelchair. Existing ramp is short and he is slowly loosing power in one arm so finding it difficult hauling himself up. Plus years of moss and lack of washing and treating the wood has not helped.
There is three of these straps (7.5cm) going under with support legs. side wood and the decking boards should hold it all ridged. He just wants fine chicken wire stapled on top
Just thinking about the purpose, you might be better off putting the angle at the top of part A with part C resting on top, that way all of the force is transferred to ground via part B rather than relying on screws (worst) or nails (better) in shear as per your drawing.
Silly Car wrote: Tue Dec 30, 2025 1:37 pm
Just thinking about the purpose, you might be better off putting the angle at the top of part A with part C resting on top, that way all of the force is transferred to ground via part B rather than relying on screws (worst) or nails (better) in shear as per your drawing.
HTH
See what its like when i get the old ramp off. Other side is limited access so might be better adding an extension to post A. The three straps that will hold the decking boards are 3.5m long so it will have plenty support underneath.
