The pipe route is simple until it reaches the wood. This is the moment to change the drawing, not quietly change the joist.
Identify what is actually there
First identify the member. Solid lumber, I-joists, and engineered beams have different limitations. Record product markings where visible, the support locations, existing holes, and proposed pipe route for the designer or product technical team. Include an overall photo as well as the cut. For an I-joist, the narrow top and bottom edges are its flanges; permission for a hole through the middle web does not mean those edges can be cut.
Weyerhaeuser's TJI hole guidance is specific to those joists. Do not apply its web-hole rules to flanges, other engineered products, or ordinary lumber. The permitted detail depends on the actual member and conditions. The manufacturer's February 2026 framing sheet explicitly prohibits cutting or notching TJI flanges.
Give the pipe another option
A lower ceiling zone, a shifted fixture, or a different routing may be preferable to a structural alteration. Have the plumber and designer compare those options before the room layout becomes fixed.
Identify the wood before interpreting a hole chart
End view: identify the parts
The wide top and bottom members are flanges. The thin central panel is the web. Do not apply ordinary solid-lumber drilling rules to this assembly.
Side view: preserve both flanges
Manufacturer-approved holes belong in permitted web locations. Cutting or notching a flange damages a different part of the member and requires an engineered response.
Hole size, position and spacing depend on the joist series and manufacturer's tables. Check those before cutting the web. Weyerhaeuser TJI installation guide.
Solid-sawn joist
A single rectangular wood member; its permitted holes and notches depend on the applicable design rules.
I-joist flanges
The thicker top and bottom edges; a web-hole permission does not permit cutting them.
I-joist web
The thinner middle panel; only the exact product's approved hole locations and sizes apply.
Engineered beam
LVL, PSL and glulam use their own manufacturer and design requirements.
If a cut has already happened
Send an overall photo showing supports and span, a close photo of the cut with a measurement reference, the product stamp, member depth and the distance from the damage to a support. Include adjacent holes, notches, hangers and any new cracks. Do not scrape or cut more material away to improve the photograph.
| If the cut already exists | Next action |
|---|---|
| Unapproved hole or notch | Stop further cutting and keep the area open for review |
| Severe damage, sagging or new cracking | Stop using the affected area and obtain urgent structural direction |
| Proposed repair sketch | Have the responsible designer or product technical team confirm applicability |
| Accepted repair | Record installation and required inspection before concealment |
Do not install an improvised prop or sistered board and assume the load path is restored. Temporary support also needs direction. If the pipe cannot use an approved route, compare a shifted fixture or a local soffit; basement soffit planning shows how to judge that compromise before framing.
Weyerhaeuser's field-issue notes describe why casual notches and substitutions can create avoidable repairs. A generic sistered board is not automatically the answer to an engineered-member problem.
The useful compromise is often a slightly different pipe route. Spend the design effort while changing the route is still cheaper than repairing the structure around it.
If the obstacle is a solid engineered beam rather than a joist web, use the separate LVL and PSL hole-review guide.