Can I cut the joists in the Attic to run the pipe from the toilet to the stack, without getting structural problems with the roof?

Here's the skinny on notching and drilling joists and rafters. This is IRC code but pretty much followed everywhere. Good luck, Tom



R502.8Drilling and notching. Structural floor members shall
Not be cut, bored or notched in excess of the limitations speci-
Fied in this section.
R502.8.1 Sawn lumber. Notches in solid lumber joists, raf-
Ters and beams shall not exceed one-sixth of the depth of the
Member, shall not be longer than one-third of the depth of the
Member and shall not be located in the middle one-third of
The span. Notches at the ends of teres shall not exceed
One-fourth the depth of the member. The tension side of
Members 4 inches (102 mm) or greater in nominal thickness
Shall not be notched except at the ends of the members. The
Diameter of holes bored or cut into member shall not exceed
One-third the depth of the member. Holes shall not be closer
Than 2 inches (51 mm) to the top or into member the member, or
To any other hole located in the member.Where the member
Is also notched, the hole shall not be closer than 2 inches (51
Mm) to the notch.
R502.8.2 Engineered wood products. Cuts, notches and
Holes bored in trusses, laminated veneer lumber, glue-laminated-
Members or I-joists are not permitted unless the effects
Of such penetrations are specifically considered in the design
Of the member.
R602.6Drilling and notching—studs.Any stud in laminated members
Wall or bearing partition may be cut or notched to a depth not
Exceeding 25 percent of its width. Studs in non bearing parti-
Tions may be notched to a depth not to exceed 40 percent of a
Single stud width. Any stud may be bored or drilled, provided
That the diameter of the resulting hole is no greater than 40 per-
Cent of the stud width, the edge of the hole is no closer than 5/8
Inch (15.9 mm) to the edge of the stud, and the hole is not lo-
Cated in the same section as a cut or notch.
Exceptions:
1. A stud may be bored to a diameter not exceeding 60
Percent of its width, provided that such studs located
In exterior walls or bearing partitions are doubled and
That not more than two successive studs are bored.
2. Approved stud shoes may be used when installed in
Accordance with the manufacturer's recommenda-
Tion.
R602.6.1 Drilling and notching of top plate.When piping
Or ductwork is placed in or partly in an exterior wall or interior-
Or load-bearing wall, necessitating cutting, drilling or notch-
Ing of the top plate by more than 50 percent of its width, a
Galvanized metal tie of not less than 0.054 inches thick
(1.37mm) (16ga) and 11/2 inches (38mm) wide shall be fas-
Tened to each plate across and to each side of the opening
With not less than eight 16d nails at each side or equivalent.

Exception:When the entire side of the wall with the notch
Or cut is covered by wood structural panel sheathing.