Valley boards - on top or between?

[high chaperal]

Advice needed!

My cowboy builders have walked off the job and left me with a half finished roof.

I can finish the work myself but I am concerned about the valleys. Its a 25 degree roof with diminishing rafters meeting the exisiting 25 degree roof. 25x 25mm batterns used.

My concern is that the valleys boards (lead valley) are 18mm thick and laid on top of the rafters - this leaves little or no depth to the valley and the underslating climbs up onto the lead.

Am I correct in thinking that for a roof this shallow the boards should be between the rafters or is laying them on top normal practice (I thought it was only acceptable on steep angles).

[leebwk]

Hi

Usually the boards are laid on top of the rafters and then the tiling batten runs upto the boards then the tiles lap over the lead