What a Preliminary Material List Contains
A preliminary material list contains section sizes, approximate lengths (typically cut from member work-point-to-work-point dimensions plus standard overrun allowance), quantities, and material grades for all primary structural members. It does not include connection plates, bolts, or hardware — those require connection detailing to be complete. The primary members — columns, girders, and primary beams — are the long-lead items this list is designed to support.
When to Issue It
A preliminary material list can be issued as soon as the structural member layout is complete and member sizes are confirmed in the model — typically within the first 1–2 weeks of modeling. It should be clearly marked 'PRELIMINARY — FOR MILL ORDER PLANNING ONLY' and accompanied by a note that lengths and quantities may change when connection detailing is complete. The fabricator uses it to place mill orders, knowing that small length adjustments can typically be absorbed by the mill lead time.
How to Use It Without Overcommitting
Order from the preliminary list with sufficient lead time that the final BOM can be issued before the material arrives. If the final BOM changes a section size or increases a length beyond the ordered piece, the fabricator may need to place a supplemental order or have the mill revise the original. Communicate any potential changes to the preliminary list as early as possible so the mill order can be modified before it is released to production.
Which Members Belong on a Preliminary List
Not all steel members require the same lead time, and the preliminary material list should prioritize accordingly. Wide-flange sections in heavy weights — W14x193 and above, W33 and W36 girder sections in heavier weights — have the longest mill lead times, typically 8 to 14 weeks from order to delivery. Standard sections in lighter weights are often available from service center stock in 2 to 4 weeks. The preliminary list should flag each entry by its expected lead time category — mill-order required vs. service-center available — so the purchasing department can sort orders by urgency. Generating this flag from the Tekla model requires either a user-defined attribute or a post-processing filter against a standard lead-time reference table.
- Heavy wide-flange columns (W14x193 and heavier) — mill order required, 8–14 weeks
- Large W-shape girders (W33x, W36x, W40x in heavier weights) — mill order required
- Standard beams in W8, W10, W12, W16, W18, W21, W24 — service center available
- Non-standard HSS sizes not in standard stocking programs — mill order required
- High-strength plate (A572-65, A514) — specialty mill order, up to 16 weeks
- Anchor rods in large diameters (1-1/2" and above in F1554 Grade 105) — specialty order
How the Preliminary List Changes Between Issue and Final BOM
The final bill of material issued with the approved shop drawings will differ from the preliminary list in several predictable ways. Member lengths will be revised — preliminary lengths are based on work-point-to-work-point dimensions without connection setbacks; final lengths reflect actual end preparation. Some member counts may change if the structural design is modified during the approval process. Material for members that were added by addendum will appear in the final BOM but not the preliminary. The fabricator should document the preliminary list order against the final BOM after connection detailing is complete and identify any quantity or size changes that require order modifications.
Generating a Preliminary List from Tekla
Tekla Structures can produce a preliminary material list through a custom report template that extracts only the primary members — beams, columns, braces — at their work-point-to-work-point lengths without connection detail. The report can be configured to apply a standard overrun allowance (typically 1/4" per end for saw kerf and end squaring) to each member's theoretical length. The resulting list includes piece marks (preliminary, since connection geometry may revise them), section sizes, grades, approximate lengths, quantities, and weights. This report can be issued as a PDF or CSV within two weeks of model setup — often while connection detailing is still in progress.
Coordinating the Preliminary List with the EOR
Before placing mill orders from a preliminary material list, confirm with the EOR that member sizes are final. A preliminary list issued from a model built on design drawings that are still in revision can include member sizes that the EOR subsequently changes — and a mill order placed on those sizes becomes a cost issue when the revision arrives. The most reliable approach: confirm in writing with the EOR that the structural framing is frozen before the preliminary list is issued and before any orders are placed. If the EOR cannot provide that confirmation, place orders only on the sections you have highest confidence in (heavy columns that have been confirmed in the column schedule, for example) and defer others until the structural documents are more stable.