Of course there never is one, but perhaps an interesting diversion. Here's a starter.
Stair carpet. I think a house that is actively being DIYed will get through stair carpet about 10 times faster than one not being. Our last one has been down 4 years and it is knackered, and it wasn't the cheapest either. Fortunately it is only the stairs itself so should only be about 150 quid.
What and why?