Collar ties: what it means on an inspection

Use this diagram

Copy this HTML to show the diagram with a credit link<img src="https://raftertie.com/charts/raftertie/collar-ties.svg" alt="A gable roof cross-section with a collar tie across the upper part of the attic, wind uplift arrows above the roof, and a dashed line at the wall plates for the ties that resist thrust" width="100%"><p><a href="https://raftertie.com/guides/collar-ties?utm_source=embed&amp;utm_medium=referral&amp;utm_campaign=figure_embed&amp;utm_content=collar-ties.svg">The collar tie sits high and resists uplift. The low tie resists thrust. by Rafter Tie</a></p>

How to check a collar tie

1. Find the height. Stand in the attic and look at where the board sits between the plate and the ridge. A collar tie sits high, near the ridge, within the zone the code sets. If a board sits low, near the plates, it is behaving as a rafter tie, and the question changes.
2. Check that it joins opposing rafters. A collar tie works as a pair connector. A board nailed to one rafter, or to rafters that are not opposite one another, is not doing the job.
3. Look for spacing. Collar ties are not needed on every pair in many roofs, and the code sets how often they are needed. Read the spacing rule in your edition; do not assume every rafter pair gets one.
4. Check the fasteners. The board resists a pull along its length, so the nailing at each end is what counts. Compare it with the connection requirement in your code book.
5. Do not count it as a rafter tie. A board high in the attic adds little against outward thrust. The code asks for collar ties because of uplift.

Common mix-ups

• Collar tie versus rafter tie. Height is the quick test. Low and holding the rafter feet together is a rafter tie. High and joining the two roof planes is a collar tie. A roof usually needs the low tie and may also need collar ties.
• Collar tie versus ridge strap. A ridge strap is a metal connector across the ridge, not a board between rafters. Check your edition before you accept one in place of collar ties.
• Collar tie versus purlin brace. A purlin brace carries rafter load down to a wall. A collar tie only holds the roof planes together.
• More collar ties do not fix missing rafter ties. Adding boards high in the attic leaves the walls with nothing resisting outward thrust.

Collar ties on the B1

Collar ties sit in the roof and ceiling area, which is 14% of the B1, in Chapter 8 of the IRC. The usual question asks you to tell the tie types apart from a description, or to place a tie at the right height. Look the topic up by name in your chapter table of contents and write the section number in your own book once you have confirmed it for your edition.

Practice it

Compare the two kinds of tie again on the rafter ties versus ceiling joists page, then read ridge board versus ridge beam to see why a ridge beam changes the tie question. When you can describe a roof's load path in three sentences, use the span table guide to check rafter and joist sizes, or return to the IRC terms glossary.

Know your collar ties? Check the rest of the B1

Take the free 10-question check. It is weighted to the seven B1 areas, scored by area and needs no signup, so you see which area costs you the most points. The Rafter Tie course adds timed practice exams, a lesson for each outline area and a study plan built from your exam date.

Sources

Show the list

• B1 Residential Building Inspector Content Outline, International Code Council.
• 2021 IRC contents and 2024 IRC contents, International Code Council. Chapters are named, not quoted; open your own copy for the text.