How to take off partitions and wall linings (plasterboard)

This guide follows French practice: French standards (NF DTU), French regulations and French bill conventions. Most sources are in French.

What you measure in a drylining package

The “plasterwork, partitions, linings, suspended ceilings” package breaks down into a few families of items, each with its own unit. In a priced bill of quantities, you will almost always find the following lines.

The first job is to read the specification and the bill format. They set the unit of each item, what it includes (tape, angles, insulation, extras) and the method of measurement. Two contracts can have different rules for the same item: an accurate take-off is first of all one that follows the rules of the document you are filling in. Workmanship, on the other hand, is covered in France by NF DTU 25.41 for plasterboard work and NF DTU 25.42 for insulated linings; these standards say how to build, not how to measure.

One item per system, not one “plasterboard” item

Not all partitions are equal. The usual French designation gives the total thickness, then the width of the frame: a 72/48 is 72 mm thick on 48 mm studs, i.e. one 12.5 mm board on each side; a 98/48 has 25 mm of board per face, a thick board or two 12.5 mm boards depending on the system. Manufacturers' data sheets point out that the height limit, fire resistance and sound insulation depend on the exact configuration: number of boards, insulation, stud spacing, single or double frame.

For the take-off, the consequence is simple: one item per system. Standard 72/48, moisture-resistant 72/48, 98/48 with insulation, fire-rated partition, lining with a given insulation thickness: each has its line, its rate, and therefore its quantity. Lumping everything into one “plasterboard partitions” line means recounting the lot on the day the prices come in.

Measuring the lengths

The length of a partition is taken from the floor plan, segment by segment. A few rules avoid most of the differences between two quantity surveyors:

• Stop each line at the face of the wall it meets. At a T-junction, the incoming partition stops against the one that continues; otherwise the thickness of the second one is counted twice.
• Keep the same measuring line for the whole project (the partition centre line or one of its faces) and note it in your assumptions.
• Measure a wall lining on the room side, on the wall actually lined, not on the centre line of the structural wall. Internal corners shorten it, external corners lengthen it: on a stepped façade the difference shows.
• Pick out ducts and boxings. Drawn small, they are easily forgotten; they often have a line of their own.

Choosing the right height

The area of a partition is its length multiplied by its height, and this is where the biggest differences arise. Depending on the specification, a partition stops below the suspended ceiling or goes up to the slab, for instance for sound insulation between flats or for fire compartmentation. On a floor where the ceiling is at 2.50 m and the slab at 2.70 m, those 20 cm add 8% of area to every metre of partition.

Read the section and the details before entering any height, and create separate items when two heights coexist on the same floor (flats and common areas, for example).

Openings and voids not deducted

A door opening or a window interrupts the partition or the lining. There are two approaches, and the contract says which one applies:

• Openings deducted. The area of each opening, width × height, is taken off. Reveal returns, frame casings and reinforcement are then paid separately, per linear metre or per item.
• Voids not deducted. Below a threshold, expressed in m² per opening, the opening is not deducted. The area counted in excess pays for the work around the opening: cutting, reinforcement, reveals. There is no universal threshold: it is set out in the specification or the bill.

A frequent mistake is mixing the two: deducting all openings without counting the reveals, or leaving openings undeducted and charging every reveal on top. Another is deducting a door over the full height of the partition instead of its opening height: on a 2.50 m partition, a 0.90 × 2.10 m door taken off “full height” removes 0.36 m² too much.

One face or two?

The quantity of a partition is usually its area seen from one side: length × height. The rate per m² of partition then covers the frame, both boards and, depending on the specification, the insulation and the joints. Items done face by face, such as skim, paint or a wall covering, are counted on each face instead. The definition of the unit in the bill decides, not habit.

Suspended ceilings and perimeter angles

A suspended ceiling is measured room by room, as an area. Voids and large openings are taken off; recessed light fittings, vents and access panels are usually extras counted per item. The perimeter of each ceiling gives the length of perimeter angle or edge joint: it follows from the area, so there is no need to measure it a second time.

Worked example

A flat with a finished ceiling height of 2.50 m, partitions stopping below the ceiling. The specification requires openings to be deducted, except those under 0.50 m² (threshold taken for the example).

72/48 partitions

Lining of the external wall

Living room suspended ceiling

If the same partitions went up to the slab, at 2.70 m, the gross area would rise to 18.40 × 2.70 = 49.68 m²: 3.68 m² more, before the doors are even considered. This is the difference most often found between two take-offs of the same drawing.

The most common mistakes

• A single height for the whole project, when the sections show several.
• Systems mixed in one line: standard, moisture-resistant, fire-rated, acoustic.
• T-junctions counted twice, linings measured on the wall centre line.
• Doors deducted over the full height, or openings deducted when the contract says voids are not deducted.
• Ducts, boxings and bulkheads forgotten because they are drawn small.
• No record of the calculation: impossible to answer a client's question three weeks later.

Doing it in Kotelys

In Kotelys, each system becomes a type: a name (“Partition 72/48”, “Lining 13+100”), a colour on the drawing, a total.

• Partitions and linings are drawn with the Length tool. With a height given to the type, every metre drawn becomes m² of wall, written out in full: “18.40 ml × 2.50 m = 46.00 m²”.
• Each opening is placed on the line with its own height (door, window, full height or a value you enter): only its area is taken off. The “Openings not deducted below … m²” setting applies your contract's rule for voids not deducted, type by type.
• Suspended ceilings are drawn with the Area tool, voids as deductions; the perimeter of each area is written in the take-off calculations and in Excel, for the perimeter angles.
• Access panels and openings are counted with the Count tool.
• One zone per flat or per floor, and the reports break the quantities down. The PDF take-off calculations write out every calculation (gross, openings, net); the Excel workbook gives the summary and the object-by-object detail.

Kotelys does not read the specification for you: the height, the threshold and the split into items remain your choices. That is precisely what makes the take-off checkable.

Further reading: drylining and ceiling take-off in Kotelys, and the other guides.

Sources

1. FFB, « Ouvrages en plaques de plâtre : les NF DTU 25.41 et 25.42 illustrés »
2. AFNOR, NF DTU 25.41 « Ouvrages en plaques de plâtre »
3. Siniat, data sheet for the Prégymétal D72/48 partition (build-up, height, fire, acoustics)
4. Éduscol STI, CAP MPI 2021 technical file: example of a specification setting the method of measurement

Thresholds and values described as “taken for the example” are not rules: those of your contract (specification, bill of quantities) always prevail.