stairs resting on chipboard

[pejoli]

Hi all,

Had the loft stairs put in yesterday - they are a straight run supported at the top by a steel. The stair man has notched the stringers in such a way that they don't lean 'against' the steel (like a ladder would against a wall), but the stringer makes contact only on the top. The newell has been notched, and doesn't actually touch the steel, either on top or on the side - all the load is going through the small surface area of the stringers, plus the screws through the left hand stringer into the wall.

My concern is that on top of the steel is the chipboard flooring and the stair risers and newell post sits on top of this (and there's the groove in the T&G flooring, so the actual width of chipboard providing support under each riser is less than an inch). The joist supporting the length of the landing will also run into the newell post there, so that the load of the joists plus people on landing is also being taken on the chipboard.

Obviously the steel is directly underneath the chipboard taking the load, but is chipboard safe to use under compression in this way - is it subject to breakdown, or at risk if it gets wet (the builders tell me it's waterproof, so shouldn't ever happen).

Appreciate any thoughts, hopefully just to put my mind at rest.

Cheers!

 

[pejoli]

Minor edit to the above - got my stringers and risers confused!

Any comments? How about an easier question:

- should a set of straight stairs transfer the load to a top beam from the top or from the side e.g. should it lean against it like a ladder? Is one way better in terms of forming a stable 'triangle' to prevent any movement? Or doesn't it matter?