Best ways to attach planks for stairs
Posted 20 August 2012 - 12:12 PM
I'm build a 4 step, free-standing staircase to access a patio. I picked up some reclaimed douglas fir. Probably not the best wood for stairs, but it's old, so well seasoned, and the planks are 2 1/2" thick, which I assume will compensate for its softness. The steps will be about 30" wide. The steps will not have a stringer or riser, instead, each step will rest on two uprights pieces from the same plank. So my question is what's the best way to attach to step to the uprights. Then, I want to attach the completed steps to each other. I was planning to glue and dowel them, but don't know what's the right size dowel to use on wood that thick and soft. I don't want to the dowels to show through. Also, if I end up attaching extra braces underneath, how thick should the screws be? I guess I'm concerned that with the softness of the wood the screws could work themselves free.
Posted 20 August 2012 - 12:43 PM
Before we get too far into sorting out the joinery it is slightly concerning that you keep mentioning the softness of the wood!?
When you say it's soft how soft? Douglas fir is typically pretty hard wearing and I would not class it as a particularly softwood to the touch... is there a chance the wood has suffered from any sort of rot?
2 1/2" thick panels will easily be strong enough to take someones weight. Glueing and doweling them is a good idea but I would also use glue blocks on the inside of the legs to give you some long grain to long grain gluing surface.
To attach the steps together you could use biscuit or dowel joints and if necessary place a batten across both legs to help support it. The screws can project as far as 2 inches into the leg, just so long as it doesn't come through the face. So if you use a 1 inch batten then a 3 inch screw would be good.
You could also use slip tenons to make a decent sized and strong tenon joint in wood that thick.
I have heard that dowels should be roughly one third the thickness of the board being jointed. However it is usually fairly obvious visually if the dowel is too big or too small so rely on your judgement to select a size that works for you.
I hope this helps
Posted 21 August 2012 - 05:25 AM
As far as softness of the wood, I mean, as in from a conifer. The condition of the wood is very good. I only do little bits of woodwork here and there, after being pretty dedicated way back in my school days. The only time I've worked with douglas fir was painting my new front door. I had to sand very lightly since it comes up so easily. So I just wasn't sure how well it would take a screw etc.
Posted 22 August 2012 - 09:42 AM
I would say unless there is any obvious signs of rot or decay then it will take and hold a screw just fine.
Enjoy the project .