Finished venetian blinds Specification: What Each Number Actually Changes

The datasheet for finished venetian blinds lists six or eight numbers, and most buyers compare the first one. That is the mistake this page is about: the numbers interact, and the one you ignore is usually the one that produces the claim.

Why the headline number is the least useful one

Every quotation leads with headrail. It is easy to compare and it is the number the factory can hit most cheaply. But it tells you almost nothing on its own: headrail sets the frame, and the parameters below set whether the product survives its first year in service. A buyer who compares only the headline figure is buying a sample, not a supply agreement.

For finished blinds, the practical rule is to fix the headline figure at the level your product needs and then spend your negotiating attention on ladder tape / cord and cord lock. Those two are where cheap goods differ from adequate goods, and they are usually absent from the quotation sheet.

The numbers that decide performance

Read the table as a set of trade-offs rather than a checklist. Moving any single line usually costs money somewhere else, and the cheapest way to hit one figure is often to let another slip.

Headrail

Typical range: 25 mm steel or aluminium. Steel is stronger and rusts; aluminium is lighter and costs more.

Slat

Typical range: 25 / 35 / 50 mm, wood or PVC. The material decision cascades into weight, price and warranty.

Ladder tape / cord

Typical range: polyester, 12-25 mm. Tape width affects the visual and the cord friction.

Cord lock

Typical range: standard / auto-lock / cordless. The component that fails first in cheap blinds.

Bottom rail

Typical range: wood, PVC, or aluminium. Weight affects how the blind hangs and how it operates.

How to write a finished blinds specification that protects you

A specification is only useful if a substitution becomes visible. That means writing the construction and the performance together, and naming the test that proves each one. For finished blinds, the clause has to pin ladder tape / cord and cord lock, because those two separate a compliant lot from an adequate one:

50 mm basswood venetian blind, 25 mm steel headrail, branded cord lock, 5000-cycle tested, cordless with tension device to EN 13120, square within 2 mm, stain 3A, valance included

Note what is missing from that line: adjectives. No ‘high quality’, no ‘premium’, no ‘export grade’. Every clause is either a number with a tolerance or a named test. If a supplier cannot quote against a line written this way, that is information about the supplier.

Where the specification usually breaks down

The first failure is cord lock slipping. The blind creeps down and will not hold position. The cause is usually cheap zinc die-cast lock or a cord that is out of specification for diameter. The test that exposes it before you order: Cycle test 5000 up/down operations with a 5 kg load.

The second is ladder cord fraying. The cord fuzzes and breaks at the headrail. It comes from sharp edges on the headrail or an undersized pulley. Test with Visual inspection after 3000 cycles; measure cord abrasion. and write the result into the purchase order, not just the enquiry.

Both failures share a pattern: they appear months after delivery, they are hard to attribute, and the cost lands on the buyer rather than the mill. That is exactly why the test belongs in the specification and the report belongs in the shipment file.

What to put in a finished blinds enquiry

1. End use and the conditions, which together decide where ladder tape / cord has to sit inside polyester, 12-25 mm.
2. The one figure that must hold, with operation cycles named as the proof.
3. Quantity per colour and per delivery, against a typical MOQ of 200-500 sets per size and colour.
4. Destination market, because compliance changes the construction, not just the paperwork.
5. A physical standard viewed under a stated light source, not a screen proof.

With those five points we can quote against a real requirement instead of a generic range. Full ranges sit on the finished blinds page, and the manufacturing side of the same question is on our quality control page.

Questions buyers ask before ordering

Which child-safety standard applies to my market?

EU/UK: EN 13120. US: 16 CFR 1120. Canada: CCPSA. Australia: the corded internal window coverings regulation. They are not interchangeable, and a generic certificate is not evidence.

Can you supply made-to-measure?

Yes, with a 1-2 mm width tolerance. For recess fitting, tell us the measuring method you use, because inside-recess and outside-recess need different deductions.

What is the cycle life of your cord lock?

Specify 5000 cycles at 5 kg on the assembled blind. Cheap locks fail around 1500-2000 cycles, which is one or two years in a hotel.

Failure modes worth a clause in the purchase order

Claims rarely come from a batch that was obviously wrong. They come from a ladder tape / cord figure that sat inside the quoted band and outside what the product needed.

The other two, with acceptance numbers attached, are in the full failure analysis for finished blinds. A supplier who cannot name the mode he sees most often is describing a catalogue, not a process.

Seven lines that turn a quotation into a specification

Most post-delivery arguments are not about quality. They are about a document that never said which figure would be measured, on which instrument, at whose cost.

1. Cord lock: standard / auto-lock / cordless is not an answer on its own. Ask for the last three lots’ actual readings and the spread behind them.
2. Bottom rail: agree the test method with the number. Two labs, two methods, two answers, one argument.
3. Child safety (cordless / tension device / short cord): state where in the band this order sits. The middle of the band is not what a tolerance is for.
4. Width tolerance: the figure you will accept inside the 1-2 mm on the finished blind band, the tolerance on it, and the method used to measure it.
5. Price validity: the period during which the quoted figure holds, and what happens to it when the raw-material index moves.
6. Remedy: rework, replacement or credit, and the point at which each applies.
7. Sample retention: one production sample per lot stays with the mill for twelve months. Claims are settled against it, not against memory.

Related reading

• Cord lock in Finished venetian blinds
• Slat in Finished venetian blinds
• Finished Blinds vs Roller blinds