Complex sentence: In New Zealand a 1995 change to no longer require boron treatment in house framing timber, was a key factor in the leaky homes crisis, but since 2003 a series of changes have now improved the regulations.
Split into simpler sentences: In New Zealand a 1995 change to no longer require boron treatment in house framing timber, was a key factor in the leaky homes crisis. From 2003 onward a series of changes have now improved the regulations.