It is an Alberta spruce and like all conifers except yews can only be cut back as far as it is green, which is no more than an inch or two deep. So the window for major reshaping and containing has long passed. Tweak it only.

if you leave it , the only thing that will happen is add moisture to the wood

ron

I'd leave it be. They grow very slowly, so you shouldn't see much infringement (or impingement!) on the steps. I know this bothers some, but I rather enjoy seeing a plant exploring those forbidden places.

Speaking of steps, how wide are they? If narrow (i.e. less than 3'), you'll most likely have to get the pruners out sooner than later. Otherwise, this decision could easily be deferred for a year...and then another. In my opinion, it provides visual appeal with minimal risk.

IMO, that little bit of bright foliage caressing the edge of the stair, is garden magic.

Quaint.

I'd leave it be.

Right now I have petunias growing through the deck lattice. :-)