Thread: Hidden fixing of timber stair tread to metal stringer?

Metal tang fabricated on stringer and slot on end of tread, usually screwed from underneath
and screw holes filled.

Originally Posted by rustynail

Metal tang fabricated on stringer and slot on end of tread, usually screwed from underneath
and screw holes filled.

Sounds reasonable, so it could be just a piece of flat bar welded on there?

That's correct, when you cut the slot, make it blind, so you won't see the slot from the front, and you'll also need to chamfer the sides of the slot to allow for the welds top and bottom.
Kryn

Thanks, I guess there is a bit of a trade off between how deep the slot can be routed vs the width of slot vs the thickness of tread material left to bear on!

I would keep the slot in the bottom third, if not as low as possible. to allow for downward loads.

Would it be an option to drill holes in the steel and use a couple of M10 or M12 coach screws or would this be too insecure going into the end grain of the timber?

Going by that image there is a gap between the stringer and the thread. You can see the shadow of the bolts/fitting etc if you look closely

Originally Posted by paddyjoy

Would it be an option to drill holes in the steel and use a couple of M10 or M12 coach screws or would this be too insecure going into the end grain of the timber?

I'd be worried about 150kg Aunty Dot coming down the stairs in a temper on those screw points..... but I don't love the idea of the tang either from a structural integrity standpoint either....

Stair treads should be fully supported at ends. So that counts bolts out. Minimum trench for treads in timber is 12mm, so steel tangs would have to be at least that. I would use 50mm as that would allow for up screwing from underside of treads well in from ends. If necessary, slots in treads can be blind at the front only, to allow treads to be slipped in from the rear. This has the advantage of locating stringers one at a time and then fitting the treads one by one. Much easier than trying to lift the whole caboodle into position.
I realize this does not alpply to your hanging staircase, but you may be glad of it when you replace it with something more sensible

Originally Posted by Astrodog

I'd be worried about 150kg Aunty Dot coming down the stairs in a temper on those screw points..... but I don't love the idea of the tang either from a structural integrity standpoint either....

yes this could be a problem, suppose you have to design for the worst case!

Originally Posted by rustynail

Stair treads should be fully supported at ends. So that counts bolts out. Minimum trench for treads in timber is 12mm, so steel tangs would have to be at least that. I would use 50mm as that would allow for up screwing from underside of treads well in from ends. If necessary, slots in treads can be blind at the front only, to allow treads to be slipped in from the rear. This has the advantage of locating stringers one at a time and then fitting the treads one by one. Much easier than trying to lift the whole caboodle into position.

The only downside I see with cutting a slot is that after you cut the slot the thickness of the timber bearing on the metal will be reduced, it might mean you would need to use a tread much thicker than required by the standard.

Originally Posted by rustynail

I realize this does not alpply to your hanging staircase, but you may be glad of it when you replace it with something more sensible

Have you had a bad experience with hanging stairs, maybe I can convince you once it's all done This would actually be for the wall side of my hanging stairs, only one side would be hanging, like pic below.

godzilla.jpg

Originally Posted by rustynail

Minimum trench for treads in timber is 12mm, so steel tangs would have to be at least that.

Does that figure come from the Australian Standards rustynail? I was unaware of that requirement. Seems pretty deep to me.

Originally Posted by paddyjoy

yes this could be a problem, suppose you have to design for the worst case!



The only downside I see with cutting a slot is that after you cut the slot the thickness of the timber bearing on the metal will be reduced, it might mean you would need to use a tread much thicker than required by the standard.



Have you had a bad experience with hanging stairs, maybe I can convince you once it's all done This would actually be for the wall side of my hanging stairs, only one side would be hanging, like pic below.

godzilla.jpg

In this picture, the stringer is actually hidden. Could you have a slot cut in the stringer that matches the tenons cut in the treads? You'll have to find some way to stop the treads to sliding back out though.

Originally Posted by justonething

In this picture, the stringer is actually hidden. Could you have a slot cut in the stringer that matches the tenons cut in the treads? You'll have to find some way to stop the treads to sliding back out though.

Depends on how big the tenon would have to be. Is there a standard on how much you can cut away to create a tenon?

Yes basically I would like a straight version of the stairs in the picture, I plan to plaster over the steel stringer when its all done.

Originally Posted by paddyjoy

Depends on how big the tenon would have to be. Is there a standard on how much you can cut away to create a tenon?

Yes basically I would like a straight version of the stairs in the picture, I plan to plaster over the steel stringer when its all done.

I don't think it's a normal practice to cut tenons in treads at all. The only reason to do this was to create a "floating" stair case look that you asked for . I would have thought you cut away as little as possible to create that look, say 5mm right around.

If the steel stringer is hidden behind plaster, why not get this type of stringers, on one side of course.