How High?

A flying visit to Leeds today to visit my sister and her boyfriend. C and I came across this house when walking to her flat. Beside the door it reads 17'ft 3". In an effort to work out how high that it is and what it might be measuring, C stood by the door to help us work it out. We still have no idea though. She'll be mortified I used this as my blip today as well, but honestly C, this picture was the best of a bad lot today...promise!