23mm parana treads

[Arthur2]

Hi. is 23mm thick parana strong enough for stair treads at 71cm width?

Thanks.

Arthur

[Brian G]

Arthur,

On a 'normal' staircase with treads and risers, yes for walking on - but not for driving a mini down though, but who knows, it may even take that sort of loading :-)

If you are making an 'open' tread staircase (no risers) then 30mm (minimum) would be the better option.

Brian G

[Brian G]

Arthur,

I've just had a look in an old book of mine and it would seem that 23mm would be a little shy for a stair tread and I have posted some drawings on tinypics.com that may be of some help for sizing - as I'm an old dinosaur (along with the book) you will have to convert from imperial to metric measurements.

1 - - about the 'bum' info

Brian G

[dom]

Note that those drawings include a central support carriage!

[John Rumm]

A bog standard commercial prefab staircase will use 19mm MDF on the treads (assuming we are talking closed riser here), so 23mm sounds adequate.

The set I built used 19mm MDF on the treads, 12.7mm MDF on the risers and the result is solid and creak free.

I were building them for display (i.e. polished etc rather than carpeted) then I would have built them "heavier" to improve the visual appeal, and reduce the noise transmission)

[John Rumm]

That looks as if it is as much for supporting the plastered soffit below as the stairs above.

[Arthur2]

Is 23m pine stiffer than 19mm mdf?

Arthur

[John Rumm]

I would expect so. MDF is quite strong when constrained, but is fairly weak when not fixed at the edges (too much load and it de-laminates and behaves like a leaf spring!). Pine is stronger (along the grain at least), but at the same time is less dimensionally stable so more likely to come unfixed over time. Since the pine is also much stronger in one direction than the other, it lends itself to getting nice stiff treads, but you don't want too much nosing overhanging the front of the tread if you are using thinnish material.

Note that with a well made stair, the flexibility of the tread is far less important than you might think, since it is the stiffness of the riser that is supporting the tread and taking the bulk of the load (which tends to be toward the front of each tread). A 200mm deep riser of MDF or ply is of formidable stiffness vertically even if only half an inch thick (the rebate in the underside of the tread will also prevent it buckling under load. It it also worthwhile making sure the risers are very well glued, wedged, and possibly pinned into place as well to keep them in place.