Buyers argue about slat more than about any other figure in finished blinds, and they usually argue about the wrong part of it: the number itself rather than the tolerance behind it.
What slat actually controls in finished blinds
The material decision cascades into weight, price and warranty.
The number is easy to quote and hard to hold, and the difference between those two things is what you are actually buying.
For Finished venetian blinds, the working range is 25 / 35 / 50 mm, wood or PVC. Inside that band the choice is commercial; outside it, the product changes category and so does the price.
How to choose a slat option
| Option | What it changes in finished blinds | When it is the right choice |
|---|---|---|
| 25 | The lowest-cost option in the family. Ladder cord fraying is where it usually ends up. | Cost-led programmes with a short service life |
| 35 | The volume middle: enough margin for process variation without paying for headroom the end product cannot use. | Most repeat programmes, and the safest default |
| 50 mm, wood or PVC | The top of the family, where the process is controlled tightly enough to guarantee it. | A warranty, a tender, or a specification that cannot be renegotiated |
These are alternatives, not points on a scale. Slat is chosen by the application rather than by price, and a supplier who quotes one option as if it were interchangeable with another is quoting a different product.
Specifying the ceiling is only justified when the end product carries a warranty that would be expensive to honour. Otherwise it is cost without a customer-visible benefit.
The figure that decides the outcome is not slat itself but the tolerance around it. A supplier who quotes 25 / 35 / 50 mm, wood or PVC without a tolerance has not quoted a specification, and the first lot will define the tolerance for you.
How to measure slat
The reference method here is Child safety, run to EN 13120 / 16 CFR 1120, with an acceptance of pass for destination market. The method is the easy part; sampling and conditioning are where reports diverge.
Take samples from the beginning, middle and end of the run. A single sample from the top of a roll tells you about the top of that roll, and slat varies more across a run than most buyers expect.
Record the measured value rather than pass or fail. A marginal pass on slat tells you the process is running at the edge, which is the information you need before the next lot rather than after it.
Slat does not stand alone
Slat moves with ladder tape / cord (polyester, 12-25 mm) and with cord lock (standard / auto-lock / cordless). Tightening one usually costs money in another, and a supplier who accepts every tolerance without comment has either not understood the interaction or is planning to substitute.
This is why a specification written as a list of independent tolerances is weaker than one written as a construction. The list lets a supplier satisfy each line while missing the product.
The clause to write for slat
The line below is the version we can quote against without inventing anything. Slat appears with a tolerance and a test, not as a standalone number.
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
Write it once and reuse it. The buyers who avoid claims are not stricter than everyone else; they send the same well-written clause every time.
When slat goes wrong
Ladder cord fraying. The cord fuzzes and breaks at the headrail.
The cause is usually sharp edges on the headrail or an undersized pulley.
The test that catches it: Visual inspection after 3000 cycles; measure cord abrasion.
What to specify instead: Deburr the headrail, use a roller pulley, and specify a bonded cord.
None of this is visible in a quotation. It becomes visible in a retained sample and a lot record, which is why the paperwork matters more than the price on this parameter.
Four questions about slat, before you order
- What tolerance do you hold on slat, and what did your last three lots measure against it?
- Which method do you use for child safety, and which laboratory signs the report?
- When slat falls outside 25 / 35 / 50 mm, wood or PVC, do you rework, downgrade, or ship and hope?
- Which of ladder tape / cord or cord lock would you move first to hit a lower price?
The answers are more useful than a certificate, because they show whether the process is controlled or merely inspected. Full ranges for finished blinds are on the product page, and the measurement regime is described on the quality control page.
Questions buyers ask before ordering
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.
Three questions, and the answers that separate mills
If the finished blinds figures on this page is going to be decided on a call, take these three questions into it.
| Question | Answer that should worry you | Answer that holds up |
|---|---|---|
| Which test catches cord lock slipping? | “We have never had a complaint.” | Squareness — on the production lot, with the acceptance figure written into the report and not into the email. |
| May I see a report for a lot you shipped last month? | “That is confidential customer information.” | A redacted report, which carries every number that matters and none of the customer’s identity. |
| Where in the wood, PVC, or aluminium band will this order sit? | “In the middle, normally.” | A stated target and the readings behind it. Bottom rail drifting inside the band is how a conforming lot still fails. |
Failure modes, and the test that catches each one
A specification only earns its keep if it names the failure it prevents. These are the two that matter for the finished blinds figures on this page.
| Failure | What triggers it | Test to demand on the production lot |
|---|---|---|
| Safety device failure | Device not tested to the destination market’s standard. | Cord load — static load test; acceptance per standard |
| Cord lock slipping | Cheap zinc die-cast lock or a cord that is out of specification for diameter. | Colour match — D65 + dE; acceptance dE <= 1.5 |
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.
Need slat specified and tested against your end use?
Send a window schedule or a single set size and we will return a quotation with the loading plan, the safety standard that applies to your market and the lead time for the colour you need. Catalogue and current price list on request.
Related reading
- Finished venetian blinds Specification
- How to Test Finished Blinds Before You Commit to a Container
- Office fit-out and commercial interiors
Catalogue and current price list · Neutral packing and private label · Consolidation, documents and lead times
