BOM vs BOQ in Construction: How They Differ
Bill of materials vs bill of quantities: granularity, audience, and procurement vs tender pricing.
Core difference
A BOQ prices measured construction work by item for tendering. A BOM lists parts/materials for making or buying assemblies—often more detailed than a single BOQ line.
Fabricators and suppliers live in BOMs; main contractors and QS teams often work from BOQs unless a package is supply-only.
BOQ descriptions often reference specification clauses and completion; BOM lines reference SKUs, heat numbers, paint systems, or bolt grades.
Using both
A subcontract package might reference a BOQ for installation allowance while the subcontractor maintains an internal BOM for purchased components.
Consistency in revision IDs across BOM and site drawings prevents ordering wrong generations of parts.
On integrated projects, link BOQ allowances to BOM-driven procurement dates so long-lead items do not miss the programme.
Where misunderstandings cause cost
Teams assume BOQ rates include every nut and bolt while the BOM shows extras—resolve whether supply-only or supply-and-fix covers accessories.
When BIM generates both schedules, validate that quantities and classifications match the contract’s BOQ structure before tender.