I’m planning a staircase to my cabin loft, treads only, no risers. I plan to mortise in the treads from the rear, leaving several inches from the nose of the tread to the top of the stringer.
So. . . how deep should I rout these mortises to get adequate bearing, and how should I fasten them? This is a new DIY project for me–I have built some conventional notched stringer staircases, but I’m on uncertain ground here.
Specs: rise is 96″, run 120″, no middle stringer, interior span between stringers 34″. One stringer fastened to stud wall, one fastened to posts at 2′ and 8′. Stock is locally milled white pine net measure 2 1/4″ X 12 1/4″, which I will use for both treads and stringers. Varnished finish, general style rustic.
DW wants no visible fasteners. I’m thinking lag screws (size?) set flush through the stringers into the treads, heads covered with balusters and trim. Or screws angled and countersunk from tread bottoms, holes plugged. (So how do I make these plugs?) Does glue or construction adhesive play a part here?
Thanks to you pros who so generously share your experience with the weekend warriors.
Replies
The total depth of the mortise should not exceed 1/3 the total thickness of the stringer.(correct me if I'm wrong on the mortise). The top of the mortise itself can be level and square for the tread and plumb for the kick plate. The lower limit of the mortise can be at a slight angle, the open end at the back of the tread and the bottom of the kick plate. To "fasten" the tread and kick plate, insert and use a wedge to "Jam" it into place. A bit of glue with the wedge will hold it all in place.
Clear as mud, Right?????
Route your mortises with a stair-lock bit. It is essentially a shallow angled dovetail bit.
The only problem I see is that I do not belive these bits will rout much deeeper than 1/4-3/8". Since your stairs are going to be out side I would reccomend 3/4" mortise.
There may be shallow routerbits that will work.
The rub is that the treads are not routed thus the reason for the shallow angle.
But since you are using pine you may be able to get away with am steeper angled bit.
Make your wedges out of oak or some other decay resistant hard wood, because they will be sitting in a spot where water could get behind them and be trapped.
Better yet pre-seal all parts before assembly.
Use Urethane exterior glue, it will bond with anything.
Maybe a Toe-screw at the back edge of the treads for insurance.
Mr T
Do not try this at home!
I am a trained professional!
Maybe Cleats would work better outside . Just an idea.
"I was born in the country, razed in the city, I'm a natural born shaker from my hips to the ground"