Masonry Tie Bar Length Calculator
Total length, count and weight, with seismic embedment rules.
Inputs
Result
Formula
| Intensity 6-7: embed ≥ max(1000 mm, wall/5) | |
| Intensity 8-9: embed ≥ max(700 mm, wall/5) | |
| Total = embed + anchorage + hook | hook 6.25d |
| Count = (height ÷ spacing + 1) × bars per row |
240 mm wall, intensity 7, 4 m long, 3 m high, 200 mm anchorage, Φ6 at 500 mm with 2 bars per row: embedment max(1000, 800) = 1000 mm plus 200 anchorage and a 37.5 mm hook gives 1237.5 mm per bar; 7 rows means 14 bars, 17.3 m and 3.8 kg.
FAQ
Why must the tie extend a metre into the wall?
The tie anchors the infill to the frame so it cannot fall outward in an earthquake. One metre provides enough bond with the masonry to hold the panel; shorter ties pull out once the wall cracks and the panel still collapses. This detailing was learned repeatedly from the Tangshan and Wenchuan earthquakes.
Post-installed bars or cast-in starter bars?
Cast-in starters are more reliable (formed in one pour, no adhesive durability question) but awkward on site and easily bent during formwork. Post-installed bars are convenient and accurately positioned, but depend heavily on hole depth, cleaning and adhesive quality, so pull-out testing is mandatory - typically 1% of each batch, minimum three bars.
Why three bars for 240 mm walls?
To spread the anchor points across the thickness. With only two bars near the middle, the masonry faces are poorly restrained and can split through the thickness in an earthquake. Three bars - one central and one near each face - confine the full depth. At 120 mm, two suffice.
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Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.