truss roofs

[beaver74]

hi all

now i know that truss roofs are designed to a tight spec and as such cant be drilled
but i have come up against a truss roof that has been designed around 3 bed rooms and as such the floor is infact the ceiling of the lower floor which i need to wire but this needs the floor being drilled
has any one come across this befor
i will be getting the customer to contact the chippy but after a few options

 

[Engineer54]

Notching the underside of a joist effectively reduces the depth of the joist by the depth of the notch, PLUS a further reduction for a stress concentration factor. Unless you are sure (and justifiably sure as well) don't.

Tell that to all the plumbers and heating fitters that have been notching joists since time immemorial.