Vitelinfratech — Rules for buried utility and | vitelinfratech.com
How deep a conduit or duct must sit under lawns, roads and crossings — and how soil and frost change the answer.
The baseline: direct-buried conduit is normally installed at a minimum depth of 450 mm (18 in) below finished grade, with typical installations at 600–750 mm. Cover is measured to the top of the duct, so the trench itself is always deeper once bedding and surround are counted.
Crossings raise the figure. Where a run crosses a driveway, yard or road surface, cover normally increases to 750 mm (30 in), and a full road crossing is often detailed at 900 mm to stay clear of resurfacing plant and heavy axle loads.
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Telecom runs sit deeper still. Polymer telecom ducts come in 1–2 m sections and are laid at 500–900 mm, usually deeper than power duct, because a cracked telecom duct carries no fault current and separation is achieved by depth.
Ground type and climate set the deep end. Frost penetration is around 750–1500 mm in cold continental climates and close to zero in tropical ground, so a depth rule written for one region cannot be copied into another without checking the frost line first.
Width matters as much as depth on multi-way banks: a 110 mm telecom duct with 50 mm of surround occupies about 210 mm of trench width, so a 12-way bank needs roughly 2.6 m before concrete wraps are added.
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