Louver width in Plantation shutters: Range, Tolerance and How to Test It

Buyers argue about louver width more than about any other figure in shutters, and they usually argue about the wrong part of it: the number itself rather than the tolerance behind it.

What louver width actually controls in shutters

89 mm is the residential standard; 114 mm reads as premium and needs a deeper frame.

This is why two suppliers can quote the same headline price and deliver products that behave differently in the second year.

For Plantation shutters, the working range is 63 / 89 / 114 mm. Inside that band the choice is commercial; outside it, the product changes category and so does the price.

How to choose a louver width option

These are alternatives, not points on a scale. Louver width 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.

The middle is where most programmes should sit, and it is the hardest position to defend in a price meeting because it has no story attached to it.

The figure that decides the outcome is not louver width itself but the tolerance around it. A supplier who quotes 63 / 89 / 114 mm without a tolerance has not quoted a specification, and the first lot will define the tolerance for you.

How to measure louver width

The reference method here is Light gap, run to assembly measurement, with an acceptance of <= 3 mm. The method is the easy part; sampling and conditioning are where reports diverge.

Measure on the goods as delivered, not on the greige or the pre-finished material. The figure that matters is the one in the product your customer receives.

Record the measured value rather than pass or fail. A marginal pass on louver width tells you the process is running at the edge, which is the information you need before the next lot rather than after it.

Louver width does not stand alone

Louver width moves with frame type (L-frame / Z-frame / deco frame) and with material (basswood / PVC / MDF / hybrid). 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.

When you change louver width, re-check the two neighbours before you approve the sample. Most of the samples we re-make are caused by a change in one figure that was not followed through.

The clause to write for louver width

The line below is the version we can quote against without inventing anything. Louver width appears with a tolerance and a test, not as a standalone number.

Plantation shutter, basswood, 89 mm louver, L-frame, 3 panels, hidden hinge, light gap <= 3 mm, painted to RAL 9010, moisture content 8-12 %

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 louver width goes wrong

Visible light gaps. Daylight shows through between panels and frame.

The cause is usually frame out of square, or panels machined without a jig.

The test that catches it: Assemble on a flat table, measure gaps at three heights.

What to specify instead: Jig-based machining plus a final assembly check; specify <= 3 mm and inspect every unit.

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 louver width, before you order

1. What tolerance do you hold on louver width, and what did your last three lots measure against it?
2. Which method do you use for light gap, and which laboratory signs the report?
3. When louver width falls outside 63 / 89 / 114 mm, do you rework, downgrade, or ship and hope?
4. Which of frame type or material 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 shutters are on the product page, and the measurement regime is described on the quality control page.

Failure modes worth a clause in the purchase order

Claims rarely come from a batch that was obviously wrong. They come from a louver width 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 shutters. 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. Frame type: agree the test method with the number. Two labs, two methods, two answers, one argument.
2. Material (basswood / PVC / MDF / hybrid): state where in the band this order sits. The middle of the band is not what a tolerance is for.
3. Panel configuration: the figure you will accept inside the 1-4 panels per opening band, the tolerance on it, and the method used to measure it.
4. Hinge (hidden / aluminium / stainless): name the number, not the word. If the answer only repeats the band, ask which point inside it is being offered for this order.
5. Deviation rule: anything outside the agreed bands is reported before shipment, not after arrival.
6. Packing and marking: shipping mark, roll or carton count and the tolerance on quantity, since a short shipment is a claim too.
7. Who inspects: third-party, in-house or none, decided in advance, with the AQL level written down.

Related reading

• Plantation shutters Specification
• How to Test Shutters Before You Commit to a Container
• Plantation shutters