Tagged: step stool strength
21 November 2018 at 6:36 pm #553392GfBMember
My parents have “commissioned” me to build my mother a step stool. They requested one in the general style of the one shown. I can plan and build a stool using the 3 standard joints (dovetail, dado, and mortise/tenon). Made from red oak, glued, and without hardware, should I be concerned about the strength over time, where it is expected to support up to 250lbs (no, she doesn’t weigh that much, but others may use it) of shifting, repetitive weight?
21 November 2018 at 7:12 pm #553396Matt McGraneParticipant
GfB, I made something similar earlier this year from recycled oak. I dovetailed the upper and lower steps into the uprights. And the horizontal rail supports are also dovetailed into the uprights. I expect this stool will long outlast me and whoever owns it after I’m gone, though I don’t use it every day (but do use it fairly often). It easily holds my 153 pounds and could easily hold a 250 pounder with hard use.
Now, I do think there are things to consider in the design. If you use dadoes to join the steps to the uprights, then the horizontal rails will be all that keeps the stool from racking. Dovetails are far stronger than dadoes in that respect. So if you do use dadoes, then think about mortising (or dovetailing) the rails into the uprights. If you use mortise and tenon, maybe used a wedged through tenon for added strength against the racking.
Just a few thoughts – hope that helps. I’ve added a couple photos of my stool to give you ideas. Note that the uprights get wider (front to back) near the floor – this really adds a lot to the stability.
Matt, Northern California - Started a blog in 2016: http://tinyshopww.blogspot.com/21 November 2018 at 7:32 pm #553400
Matt, thank you for sharing this. This is basically what I was planning, and I hope you don’t mind me stealing your plans? 😉 . Your note on sloping the uprights is a good idea. The only thing I think I’d like to change is making all the dovetails into the uprights half-blind so the sides are smooth.
After I build, I’ll get up on it with my 194lbs, and do a little “surfing”. If don’t get back to you, I probably died.22 November 2018 at 1:58 am #553403Matt McGraneParticipant
Steal away, but if you do it like mine you may want to have less of a “rise” for each step, especially if your mom is elderly or not too strong. Mine has steps at 9″ and 18″ off the ground and that’s too much for some people. I’m sure you have your own plan for this, but just saying … Good luck on the project!
“If don’t get back to you, I probably died.” –LOL
Matt, Northern California - Started a blog in 2016: http://tinyshopww.blogspot.com/23 November 2018 at 1:21 am #553419EdParticipant
@awesomeopossum74 Search for images of a step stool with handle and see if your mother might like that. The “handle” extends up from the steps to hip height or a little higher. It can be used to carry the stool, but it also provides a handrail to help with balance while up on the step.10 December 2018 at 2:47 am #553810
Interesting project with its design considerations.
Musing on the dovetail approach, I wonder how robust they would be to careless foot traffic … though hiding them “half-blind” would help, in some ways.
I’d be tempted just to dado the sidewalls into the base of the treads, most of the force on the treads is downwards.
I think the cross pieces under the treads and one at the back are enough to prevent racking provided they’re not too narrow, given theyre glued long grain to the treads. Three or maybe four inches wide. I like the idea of the arches in the orig design to lighten them visually while keeping the width for structural reasons.
Could the cross pieces a through-tenon with a visible protruding nub (craftsman roundover), which would look cool and strengthen things markedly? They’d need haunches at the top obvs.
I’m a beginner who’s curious about the engineering considerations that go into furniture design, so be interested to hear feedback or further discussions!12 December 2018 at 7:01 pm #553828
Just a little update on this project. You don’t see it in this pic, but I’m working on the step dovetails.
My son decided to “test” it for me, and said it feels very sturdy so far.12 December 2018 at 7:16 pm #553830
[quote quote=553419]@awesomeopossum74 Search for images of a step stool with handle and see if your mother might like that. The “handle” extends up from the steps to hip height or a little higher. It can be used to carry the stool, but it also provides a handrail to help with balance while up on the step.[/quote]
Yes, this is a good idea, and something I’m considering! I don’t want my mother to have to bend over to pick up the stool.
Musing on the dovetail approach, I wonder how robust they would be to careless foot traffic … though hiding them “half-blind” would help, in some ways.[/quote]
I’m not sure what you mean by careless foot traffic, as it relates to the dovetails? Can you elaborate?
[quote quote=553810]I’d be tempted just to dado the sidewalls into the base of the treads, most of the force on the treads is downwards.[/quote]
I thought about that for a while, as I argee most of the force is downward. But I decided to go with dovetails to help prevent as much lateral racking as possible.
[quote quote=553810]I think the cross pieces under the treads and one at the back are enough to prevent racking provided they’re not too narrow, given theyre glued long grain to the treads. Three or maybe four inches wide.[/quote]
I’m not able to measure at this moment, but I think I went with 2.5″ cross members with 2 dovetails. They seem pretty stout so far.12 December 2018 at 9:17 pm #553831
Assuming I understood you right, the endgrain of the dovetails are at the ends of the stair treads. My concern about “careless foot traffic” is that clumsy feet stepping on/off can clip that edge and the endgrain of the dovetails/pins, and potentially cause long shards splitting off. The half blind helps because there is no endgrain on the flat of the stair tread; only issue I saw with that is if you only leave 1/8″ timber then as you get wear the thin timber would be a little vulnerable – prob fine with thickish treads and 1/4″ or more timber left. I’m envisaging a fairly high wear and daily usage environment like a busy family kitchen as opposed to delicate handling in a mahogany panelled library room.
2.5″ cross pieces sounds plenty on reflection, and will look a lot better than wider. I was certainly getting carried away with 4″, would be heavy visually even w an arch.
Thinking about aprons under chair seats, they are structurally not dissimilar, carry bodyweight plus probably more racking forces, and generally don’t get all that wide.
Do post photos once you get going!12 December 2018 at 11:56 pm #553832
Sorry, should read more carefully, I now see the photo: it looks great! Nicely done joints.
In oak I imagine it will be bombproof. I’ve only used pine so was envisaging that.13 December 2018 at 12:29 am #553835Larry GeibParticipant
Another way to go is along the lines of Wharton Esherick’s Step stool.
Here is a three step version.
The handle helps position the stool and steady the user. If you hunt around, there are plans online.
25 December 2018 at 7:36 am #554099
- This reply was modified 4 months, 1 week ago by Larry Geib.
Wow, that is a stunning piece, thanks for sharing it Larry.27 December 2018 at 3:54 pm #554119SandyParticipant
If I were making this for an elderly person, I would consider Pauls Step ladder project. It give a lot of stability and lots to hang onto. Or… just a dumb thought, you might consider bringing the items that she has to climb for, down to her level so she doesn’t risk a fall from any style stool or ladder. Other than that your stool looks great.
Insanity: doing the same thing over and over again and expecting different results.
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