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The design wind uplift pressure acting on the roof.
For THIS part of the roof, not one figure for all of it. Uplift is far higher at eaves, ridges and especially corners than it is over the middle of a roof, and the wind standards say so explicitly by dividing the roof into zones. A tie near a corner carries a load that a field pressure does not describe, and the corner zones are where roofs actually come off.
The roof area whose uplift load is carried by this collar tie.
One tie's share: half the spacing either side of it, over the length it works across. Tributary area is a bookkeeping figure rather than something you can measure, which is why it is where these calculations go wrong quietly — the check is that the areas assigned to all the ties add up to the roof, no more and no less. If they overlap, some load is counted twice and some tie is carrying more than the sheet says.
How many collar ties share the tributary area's uplift load.
Read this together with the field above, because the two can double-count each other. If the area entered is already one tie's share, dividing it again among several ties halves the load and produces a comfortable-looking answer that describes nothing. Decide once whether the area is the whole zone or a single tie's portion, and make this number agree with that decision.
Collar tie tension force
2.69 kips
Simplified tributary-area estimate — a full load path/connection analysis by a structural engineer is recommended for critical uplift connections.
They open the calculator with your figures already in it
Collar Tie Wind Uplift Tension Calculator: 2.69 kips — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Simplified tributary-area method: tie tension = uplift pressure × tributary roof area ÷ number of ties sharing that tributary area
Inputs used
- Wind Uplift Pressure
- 31.33 psf
- Tributary Roof Area per Tie
- 86 sq ft
- Number of Ties Sharing This Load
- 1
Confidence note: Simplified tributary-area estimate — a full load path/connection analysis by a structural engineer is recommended for critical uplift connections.
What this calculation does not cover
- One uplift pressure is applied to every tie on the roof. Component-and-cladding pressures are not uniform: the ridge, eaves, hips and corner zones carry substantially more than the field of the roof, often half again or double, so the ties nearest those edges see more than this figure and the ones in the middle see less.
- The result is gross uplift with nothing set against it. The roof's own weight resists lifting and the wind combination credits part of it — 0.6 dead against 0.6 wind in allowable stress design — so tension taken straight from a pressure overstates the net force. It can also understate it: if the pressure entered is external only, internal pressure in a partially enclosed or breached building pushes up from underneath and adds to it.
- The force lands in the tie, but the tie is not what fails. Collar ties come apart at their nails, so this figure has to be converted into a fastener count using the lateral design value for that nail in that species and member thickness, with end and edge distance enough to develop it — three nails in a 2x4 is a habit rather than a capacity.
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This result is a specification — 2.69 kips — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.1.1
Regulatory standards & verification citations1
- Simplified tributary-area method: tie tension = uplift pressure × tributary roof area ÷ number of ties sharing that tributary area
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