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I-Joist Hole Guide

What it's for

Checking whether you can cut a hole in the web of an I-joist, and where. It is for TJI® joists, made by Weyerhaeuser; Housewright Calc is not affiliated with or endorsed by Weyerhaeuser. You give it the joist series and depth, the clear span and the hole, and it tells you whether the hole is allowed, how far it has to stay from the supports, the longest span the joist is tabulated for, the minimum bearing, and a drawing of the joist with the no-hole zones hatched. The numbers come from the manufacturer's published tables, not a building code. It is for TJI joists only.

Step by step

This example uses the numbers the screen opens with.

I-Joist Hole Guide inputs: the answer bar reads Within hole table, a green Within the manufacturer's hole table and End clearance 2' 0" · Hole 4". Then SERIES TJI® 210, DEPTH 11⅞" (9½", 14" and 16" beside it), CLEAR SPAN 16' 0", SUPPORT CONDITION Simple (Continuous and Cantilever beside it), JOIST SPACING 16" o.c. (12", 19.2", 24"), DEFLECTION LIMIT L/360 (L/480 beside it), FLOOR LOAD 40 / 10 psf (40 / 20 psf) and HOLE SHAPE Round (Square, Duct), with HOLE SIZE below the fold. 1 2 3 4 7 8
Steps 1 to 4, then 7 and 8. Steps 5 and 6, THIS SPAN and CANTILEVER LENGTH, show only for a Continuous or Cantilever joist.
  1. SERIES — the TJI series you are using. Tap and pick from the list.
  2. DEPTH — the joist depth. The choices change with the series.
  3. CLEAR SPAN — inside face of one support to inside face of the other. The example is 16' 0". It is not Floor Joist's FLOOR WIDTH (OUTSIDE OF RIM): take off the rims and the bearing before you type it here.
  4. SUPPORT CONDITION — Simple is one span with a support at each end. Continuous runs over a middle support. Cantilever runs past its support. It sets how far from the bearing a hole has to stay.
  5. THIS SPAN — Continuous and Cantilever only. End span: the left support is the joist's end support. Interior span: both supports are middle supports (the middle span of a joist over three or more spans). Not sure, the default, holds the larger of the two distances at the left support.
  6. CANTILEVER LENGTH — Cantilever only: how far the joist runs past its support. The guide allows up to 24", with a backspan at least twice the cantilever; longer goes to ForteWEB or an engineer. Its reinforcement details are read by roof span and roof load, which this screen does not ask, so an amber line says they are not checked.
  7. JOIST SPACING — on center.
  8. DEFLECTION LIMIT — how much bounce the span may have. L/480 is stiffer than L/360. FLOOR LOAD — live and dead load in pounds per square foot. These two, with the spacing, only change the maximum span. They do not move the hole.
I-Joist Hole Guide with SUPPORT CONDITION Continuous selected: SERIES TJI 210, DEPTH 11⅞", CLEAR SPAN 16' 0", then the new row THIS SPAN with Not sure selected (of Not sure, End span and Interior span), JOIST SPACING 16" o.c., DEFLECTION LIMIT L/360 and FLOOR LOAD 40 / 10 psf. The answer bar reads Within hole table, in green Within the manufacturer's hole table, and End support 2' 0" · intermediate 2' 0" · Hole 4". 5
Continuous (or Cantilever) adds THIS SPAN, step 5. Not sure holds the larger of the two clearances at the left support.
I-Joist Hole Guide scrolled: HOLE SHAPE Round and HOLE SIZE 4", then RESULTS reading End clearance 2' 0" · Hole 4"; table column 4" (size rounded up); Allowed centerline 2' 2" — 13' 10" from left support; Max span 21' 2"; Bearing min: end 1-3/4" · intermediate 3-1/2"; the Bonus note about one 8-7/8" round hole at the exact CENTER of a simple span ≥ 5'; and the manufacturer's rules, from DO NOT cut or notch flanges — ever. to Distances assume the maximum uniform loads in TJ-4000. For other load conditions or hole configurations, use ForteWEB or contact Weyerhaeuser. The answer bar keeps Within hole table and the green line. 9 10 11
Steps 9 to 11: the hole, then the answer and the distances under it.
  1. HOLE SHAPE — Round, Square or Duct.
  2. HOLE SIZE — the diameter of a round hole, or the longest side of a square or rectangular one. With Duct the row reads DUCT WIDTH and a DUCT HEIGHT row appears under it.
  3. Read the answer: Within hole table, with the distances under it.

Reading the results

  1. The headline is the verdict: Within hole table or Hole not permitted. If CLEAR SPAN is longer than the joist's tabulated max span, the joist comes first: the headline reads Won't span with your span, the one check is SPAN EXCEEDS MAX, and no hole zones, clearances or hole rules print until you pick a joist that spans.
  2. Where the hole can go. End clearance is the least distance from the inside face of a support to the near edge of the hole. Table column is the hole size the table was read at, in inches. If your size falls between columns, the next one up is used. For a duct it gives the row height and the width, for example 11" high × 16" wide. Allowed centerline is the range for the center of the hole, measured from the inside face of the left support. In the example that is 2' 2" to 13' 10". With Continuous or Cantilever the line gives two distances: one for the left support and intermediate for the right one, the middle or cantilever support. The guide keeps a hole one distance from an end support (its Table A) and another from a middle support (Table B), and THIS SPAN says which the left support is. End span reads End support … (Table A); Interior span reads Intermediate supports … (both ends); Not sure holds the larger of the two. Table A is the larger for some holes: a 3" round hole in an 11-7/8" TJI 210 needs 1' 6" from an end support but 1' 0" from a middle one. The drawing labels the left support MIN INT BEARING on an interior span.
  3. Max span is the longest span tabulated for this series, depth, spacing, deflection limit and load. With Continuous, where the guide's note can call for web stiffeners the line says so with the note's span: they go at the middle supports where the bearing is under 5-1/4" and the span on either side is over the figure given (17' 0" for a TJI 210 at 24" o.c., 40/10). The app knows one span, so check the other side's too. A Simple span has no middle support, so the line never says it there. With Cantilever the span check reads Backspan within the tabulated max span, and the cantilever's own lines follow. If the table has no entry it reads Span not tabulated. Bearing min is the least bearing length at an end and at a middle support.
  4. The manufacturer's rules print on every result for a joist that spans. Never cut or notch a flange. Keep web above and below the hole. Keep holes apart. The small knockouts can be used anywhere. There is also a note about one large hole at the exact center of a simple span. Read them on the screen, where the sizes are given.
The end of the I-Joist Hole Guide results: two green lines, Within the manufacturer's hole table and Within the tabulated max span, the BASIS & WHAT WAS ASSUMED row and the link Check before you cut · Measure twice, then the joist drawing headed ALLOWED HOLE ZONE — ⌀ 4", with hatched zones 2' 0" in from each support, a 12' 0" allowed hole zone and a 16' 0" clear span, the notes MIN BEARING 1-3/4" EACH END and NO FIELD-CUT HOLES IN HATCHED AREA, and the title strip I-JOIST, TJI 210 — 11⅞", NOT TO SCALE. A dimmed SHARE PDF and a lit SAVE follow, with the line Enter your own measurements to export. 5 6 7 8
The checks, the basis row, the drawing and the export buttons.
  1. The checks. Two lines, green when within the table. HOLE NOT PERMITTED means the table has no allowance for that hole in that joist. The first note says why. Make the hole smaller, change its shape, or use a deeper joist. SPAN EXCEEDS MAX means CLEAR SPAN is longer than the tabulated span. Go to a deeper joist or a heavier series, tighten JOIST SPACING, or shorten the span.
  2. BASIS & WHAT WAS ASSUMED — tap it. It says how the subfloor is assumed to be fastened for the spans and what to do if yours is not. It names the manufacturer's guide and date the tables came from, and says to verify against the current guide or the manufacturer's software.
  3. The drawing shows the joist on its supports. The hatched ends are where no field-cut hole may go. The clear zone between them is dimensioned for the hole you entered, and that hole is named above it: a bigger hole needs more room at each end, so the zone is only good for that size. On a Cantilever joist with a CANTILEVER LENGTH entered, the joist runs on past the right support by that length, dimensioned from the support's outer face; it is not hatched, because holes up to 1-1/2" may go there. Pinch to zoom, drag to pan, double-tap to reset. The expand button opens it full screen. See Reading the drawing.
  4. There is no material list on this screen. SHARE PDF makes a sheet with the drawing, the verdict and the notes. SAVE keeps the result in History. SHARE PDF stays dim until you change at least one input. SAVE stays lit, but while every input is still a default a tap only answers Enter your job's numbers first and saves nothing.
The I-Joist Hole Guide is free, results and all. The drawing, the PDF and the History buttons are part of Pro, a one-time purchase. See Free and Pro.

Common mistakes

From Floor Joist, CHECK IT IN I-JOIST HOLE GUIDE opens this guide with that floor's clear span, spacing and dead load already in.