How to build a tech pack for the garment workshop

What you will learn

Learn which fields a production tech pack must include so a workshop can sew the garment without errors or questions, and recognize the most frequent mistakes that get a sample or a whole batch rejected.

Before you start

You should already be comfortable with patternmaking, size grading and industrial cutting and sewing processes. This lesson doesn't work on the pattern: it works on the document that goes with it and that the workshop uses to produce without depending on your interpretation.

Concept

The tech pack (the technical specification sheet) is the document that translates a design into manufacturing instructions: it brings together measurements, materials, finishes and processes so the workshop sews exactly the garment that was designed. It works as the technical contract between design and production — it is not a patternmaking document, it is a communication and traceability document. It serves three functions the pattern alone doesn't cover: it removes ambiguity (without written data, every cut is resolved "at the workshop's discretion"), it is the basis of costing (fabric consumption, trims and assembly time come from the tech pack, not from the pattern) and it is the proof of what was ordered and what was approved if something comes out mislabeled or in the wrong size. With a template, a complete tech pack takes 2 to 4 hours to put together — longer for designs with several colorways or many size variants.

Lesson content

The header: identify the style without ambiguity

The header is the identification block: it can never be missing, whatever the garment.

The datum used most day to day is the internal reference code, because it is the one that appears on the cutting order and in all communication with the workshop. It helps for it to be systematic (season + category + sequential number) so any garment can be traced back.

• Style code and style name
• Season, and client or brand if you work for third parties
• Creation date and last revision date (e.g.: Rev. 02)
• Base size and status: sample, approved or in production
• Designer or person responsible for the tech pack

Base size and size chart: the section that generates the most errors

Two charts live side by side here and are often confused: the body measurement chart (the measurements of the person who will wear the garment) and the finished garment measurement chart, or POM —points of measure—, which are the real measurements of the cut and sewn piece, with design ease already included. The one that goes in the tech pack is always the finished garment chart.

It isn't enough to write "waist": each measurement point has to say at what height and by what method it is measured (for example, chest width 2.5 cm below the armhole). According to industry guides, the lack of that precision is the most common cause of variation between the sample and bulk production.

Each measurement also needs a tolerance, expressed in +/- cm or mm. As a reference: uniform tech packs work with up to ±5 mm, and t-shirt tech packs with ±1.9 cm in width and ±2.5 cm in length — it varies by measurement point and fabric. Not defining tolerances is a direct cause of batches being rejected in quality control.

• Grading rule: the difference in cm that is added or subtracted between one size and the next, per measurement point — it is what the patternmaking software uses to grade the base pattern across the whole size range.

Materials, consumption and yield

Each fabric and trim needs its own entry: code, description, supplier, unit cost, unit of measure, quantity and production cost. That complete list is the BOM (Bill of Materials). For the main fabric you also add composition, width, weight, color with a code (Pantone or another standardized system) and yield in linear meters per garment.

Consumption —in linear meters or kilos of fabric per garment— is the datum that connects the tech pack to costing and to the raw-material purchase order: it varies by size and depends directly on the efficiency of the marker (80% utilization is considered a good figure; going above 90% is already a serious technical challenge). The tech pack has to state the target efficiency the consumption was calculated with, because the cost of the garment is built on that basis.

This topic is covered in more depth in the guides on garment costing and on calculating fabric consumption from fabric yield. For this lesson it is enough to be clear that this datum is born here, in the tech pack, and is not improvised later.

Workshop instructions, labeling and technical drawing

The rest of the tech pack speaks directly to cutting, sewing and finishing, so it doesn't depend on the interpretation of whoever is on shift that day. Then comes labeling, with its own regulations, and the flat technical drawing, which describes the garment without stylizing it.

• Cutting: piece orientation (on grain, cross grain or bias), type of marker and cutting list with the number of pieces per size and material.
• Sewing: stitch type per the ISO 4915 standard (for example, 301 for a straight lockstitch for assembly, 504 for a 3-thread overlock), stitches per inch, seam allowance (the most common standard in the industry is 1 cm) and assembly sequence.
• Finishing: pressing temperature depending on the fabric, hem type and width, and quality control points before packing.
• Labeling: brand label, size label (it must match exactly the system declared in the chart), composition and care label (care symbols per ISO 3758) and the price/code label.
• Technical drawing: front and back view at minimum, dimensioned with the key measurements (not all of the POM, but the ones that define the silhouette) and with enlarged construction details of pockets, collar, cuffs and openings.

Practical example

In a t-shirt tech pack, the size chart states that size M measures 51 cm of chest width with a tolerance of ±1.9 cm, and 68 cm of total length with ±2.5 cm. That way, quality control knows exactly what difference is accepted before rejecting the garment.

Common mistakes

Filling in the size chart only for the base size and calculating the rest "by eye" or by rule of three.: Fill in all the measurement points (POM) for all sizes of the size range, not just the base.

Writing "waist" or "chest" without saying at what height or by what method it is measured.: Define each measurement point with a fixed reference, for example "2.5 cm below the armhole".

Mixing size systems: the chart uses letters (S/M/L) and the sewn label uses numbers, without clarifying the equivalence.: Declare a single size system per tech pack and clarify the equivalence if the product is exported.

Leaving the measurement chart without a tolerance column.: Add a tolerance (+/- cm) to each measurement point, depending on the type of fabric.

Describing a trim only by its name ("black zipper 18 cm") without a supplier code or unit cost.: Fill in code, supplier and unit cost on every line of the bill of materials (BOM).

Correcting the technical drawing or the pattern after a sample and not updating the bill of materials.: Version the tech pack (Rev. 01, Rev. 02...) and review all fields after any change, not just the one that prompted it.

Modeltex tip

If you work with a digital pattern that already comes with the size range solved, those finished garment measurements are a good starting point for your POM chart. Even so, always validate them against the sewn sample before sending the tech pack to the workshop.

Exercise

Pick a style you already have patterned and build its complete header (code, name, season, base size, status) plus the size chart for at least three sizes of the range, with one key measurement point (for example, chest width) defined with its measuring reference and its tolerance. Save it as a base to complete the rest of the tech pack.

Frequently asked questions

Does the tech pack replace the pattern?

No. The pattern defines the shape of each piece; the tech pack is the document that goes with it and carries everything the pattern doesn't say: materials, tolerances, assembly sequence, labeling and consumption. They are always sent together.

How long does it take to build a complete tech pack?

With a template, between 2 and 4 hours per style. It takes longer for complex designs, with several colorways or many size variants.

What happens if I don't define tolerances in the size chart?

It is one of the direct causes of batch rejection in quality control: without an accepted margin of error, any minimal difference between the garment and the chart can be taken as a defect.

What software can I use to build a tech pack if I don't have a patternmaking CAD?

Excel is enough for the size, consumption and materials charts, plus Illustrator or similar for the technical drawing, and then export everything to PDF. That combination covers 100% of the tech pack fields — patternmaking CAD is needed for the pattern and the marker, not for the tech pack itself.

Does the tech pack calculate the cost of the garment?

It doesn't calculate it, but it is the source of the data used for costing: fabric consumption per size, the quantity of trims and the assembly time come from there, not from the pattern. The cost calculation itself is covered in the guides on garment costing and on fabric consumption from fabric yield.

Summary

The tech pack translates the design into manufacturing instructions: header, size chart with POM and tolerances, materials with their BOM, consumption and yield, cutting, sewing and finishing instructions, labeling and technical drawing are the fields that cannot be missing for a workshop to produce without errors or questions. Most rejections of a sample or a whole batch come down to one of these fields being incomplete or ambiguous, not to a problem with the pattern.

Go back to the full course or ask the Modeltex Lab AI.