In February 2019, our 80’ long suspension bridge took a big hit due to an ice-snow storm. An old maple tree above it snapped and came straight for one of the support posts, taking a few trees along with it. The post snapped about in half and the bridge went sideways. The sad event is chronicled here.
The good news was that all the cables and the cable-locking system components were not affected at all. The eye bolt on the broken post that holds the main cable was bent and that was about it for damage other than the post! After a whole lot of cleaning up of debris, my neighbor and I, with some help from the photographer, installed a new (used) power pole and lifted the bridge back up.
The free-standing stairs on either side of the bridge were constructed of recycled materials way back in 2005 and the decking was not meant to be permanent either, so this disaster gave us an important reminder that we needed to do some updating on our bridge.
The decking is ready to install later in the summer and meanwhile I screwed down planks to keep the bridge safe to walk on for now. The free-standing stairs became more of a priority because they were already falling apart before the storm.
Here are some instructions that assume you have some carpentry experience. Feel free to email me if you don’t understand something.
Pieces Needed (lengths depending on the rise and run of your stairs):
2 – 4×12 pressure-treated beams (stringers)
4 – 2×4 pressure-treated lumber
5 – 2×12 pressure-treated lumber for the steps
Two rules of thumb for free-standing stairs:
1. One riser plus one tread = approx. 18 inches
2. Two treads plus one riser = approx. 28-29 inches
There are other rules of thumb, such as when dealing with landscaping and low slope terrain, but these two rules will handle almost any building situation.
When you design your free-standing stairs, you begin with “What is my total rise?” Take that total rise and see how a 7” rise and an 11” run will work (which is the recommended ratio). Divide 7 into your total rise. That will indicate the number of steps (including the landing). My stairs have a 7” riser and 11” tread measured nose-to-nose with a 35″ total rise with a 32-1/2° incline. What if you have a total rise not divisible evenly by 7? Perhaps it’s 34”. 34 ÷ 7 = 4.85. Round 4.85 up to 5. 34 ÷ 5 = 6.8 or 6-25/32 or 6-13/16. With that number, you would just leave the tread at 11”.
If it turns out that you have a total rise that is more evenly divisible by the next higher riser, say 8”, go with that. For example, a 32” rise would give you four 8” steps with a 10” tread (remember the rule of thumb).
Not to belabor this, but you could have a rise of 7-1/2” if it divided into your total rise evenly. And then the tread would be… (you figure it out using the rule of thumb*).
The other question is, “How much space in front of my stairs do I have to work with?” If you are in tight quarters and the rise would end up being more than is comfortable for walking, then you’ll make a landing and turn the stairs at an angle to gain more run that gets you to your final landing. You can also build an alternating-tread ladder stair. I built one and will blog about it soon but I think there are instructions for it online.
Process: The layout is carefully marked on the two 4×12 pressure treated beams (stringers), and cut. The steps will fit into slots in the beams and screwed from the sides. My slots are 3/4” deep.
To carve a slot, I use my skilsaw to cut multiple passes, then chisel out. It’s easy to knock out the remaining wood after cutting. The very back where the round blade doesn’t reach needs extra work.
Pre-drill the holes for the screws.
Each beam is attached to a vertical 2×4 pressure-treated piece, based upon your total rise. Also, each beam has a horizontal pressure-treated piece based on your total run. I used a wood preservative in the slots to give them extra protection from rot.
For the near-stairs, I screwed in the steps and hauled the assembly to the bridge site.
For the far-stairs, I assembled the components on-site.
Thanks for stopping by. Be sure to check out our book about building this strong bridge. Here is the link:
Images, diagrams, and text copyright 2013-2020 by Marvin Denmark unless otherwise noted. Please do not copy and post my content anywhere without my permission. Thank you.