Hydrangea Species, Climbing Hydrangea

We planted this about 5 or 6 years ago, from a 1 gallon pot. The first couple of years were lackluster, but since then it has taken off ...Read Moreand now covers completely a trellis approx. 6 ft. wide and 7 ft. high, in shaded western exposure under the drip line of a large black walnut (zone 5 or 6). Therein is the question--the trellis is about 1 ft. out from a plain barn wall, that is about 25 ft. high (two full stories). If we let it, the hydrangea would grow to cover the wall, which would be lovely--but, because it would attach to the wall, would create problems down the road with maintenance.

How much damage might the plant do to the wooden wall? How would we manage future painting of the wall (just was painted about 2 years ago--next paint job a decade away, at least, probably by next owner) If we just continue to prune, as we did last year, how do we manage the natural growth that will now be limited to the trellis space? If we extend the trellis in some fashion, either up or out, these issues would only be delayed a couple of years or so, but not resolved. We really like this plant, it is perfect for the location now--but help is needed to assure its continued existence and our continued comfort with it.