The job
Modelled, not recorded. Every figure on this page is re-run through the calculator it names whenever the site is built; the estimate is worked, but no job was carried out, so the last section gives the mechanism of each likely error rather than a measured overrun.
A stud partition is three trades standing in one line: a carpenter's frame, a dry liner's boards and a plasterer's skim, with a joiner returning at the end for the architrave and skirting. Its materials follow that sequence, and each trade's quantity is read from something the trade before it settled. The studs decide where a board edge may fall; the boards decide the screws and the joints; the joints decide the scrim; and the door lining, fitted with the frame long before anyone thinks about trim, decides the beads, the architrave and where the skirting stops. The ten quantities below run in that order because it is the only order in which each has what it needs.
The job: a 3.6 m (11.8 ft) partition, 2.4 m (7.9 ft) floor to ceiling, dividing a room on a concrete ground floor. It runs from one masonry wall to the other and across the ceiling joists above, and carries one 762 × 1981 mm (2 ft 6 in × 6 ft 6 in) door, its framed opening starting 300 mm (12 in) from one end. The frame is 38 × 89 mm (1.5 × 3.5 in) CLS at 400 mm (about 16 in) centres, each face is 15 mm (about 5/8 in) acoustic plasterboard with a 2 mm skim, and the cavity is filled with mineral wool, because the reason for the wall is that the two rooms should not hear each other.
THE DOOR IS THREE SIZES, AND THE STEPS DO NOT ALL USE THE SAME ONE. The leaf is 762 × 1981 mm. The lining that carries it measures 770 × 2000 mm (30.3 × 78.7 in) inside. The opening framed between the door studs and under the head is 840 × 2040 mm (33.1 × 80.3 in), which leaves room for a 30 mm (1.2 in) lining with 5 mm (0.2 in) of packing each side and 10 mm (0.4 in) over its head. The board deduction, the sealant and the stop bead follow the framed opening; the architrave follows the lining; the skirting follows the architrave. Framing to the leaf leaves no room for the lining, and cutting architrave to the framed opening puts every mitre in the wrong place — the two quiet ways this takeoff goes wrong.
THE SECOND IS THAT SOUND GOES ROUND A WALL BEFORE IT GOES THROUGH IT. Mineral wool and a denser board raise what the panel can stop, but an open joint at the floor, the ceiling or the ends, or a door with daylight under it, can pass more sound than the rest of the wall put together. That is why the perimeter is sealed as a step of its own, between the second face going on and the joints being scrimmed, and why this page gives no sound rating. The site's STC estimator is an American additive rule of thumb in STC points, starting from a plain single-stud wall with one layer of gypsum a side and with no field for a denser board. It is not the ISO 717 weighted rating Approved Document E is written in, so it is left off here. Where a wall has to meet Approved Document E, the build-up comes from a tested system or one of the Approved Document's own constructions, and the counts here follow it rather than set it.
WHERE THE SITE RUNS OUT. The bore-and-notch calculator works to the American IRC and NEC, so it is left off a UK page; cables through this frame follow the BS 7671 safe zones instead. Nothing on the site sizes a door lining or counts trimmers or noggins, so those come from a drawing of the frame rather than from a figure here. The stud calculator's door allowance assumes American king and jack studs, and its plate line a double top plate; this partition has no jacks and one head plate, so the door head is cut from that allowance and the plates are taken off the run by hand. Each step's headline comes from the calculator linked there, and the few hand figures, the cut lengths, the plates and the cutting lists, are arithmetic on the measurements above. The job is modelled, not recorded.
What was measured, and how
The partition line, wall to wall and floor to ceiling
3.60 m (11.8 ft) wall to wall; 2.40 m (7.9 ft) floor to ceiling at both ends and the middle, so studs cut to 2.32 m (7 ft 7 in)
Snapped on the floor, carried up to the ceiling with the laser, then measured along both lines and taken for height at each end and in the middle. The height sets the stud cut length, so one reading at mid-span hides a ceiling that dips at one end and leaves studs either loose or too long there.
Which way the ceiling joists run, and what is buried along the line
Joists cross the line at 400 mm (about 16 in) centres, so the head plate fixes into one every 400 mm; no cable or pipe on the plate lines
Found by sweeping the ceiling line with a cable and pipe detector, whose hits on the ceiling-board screws mark each joist, confirmed with a fine test hole, and the floor and both end walls swept along the plate and stud lines before any fixing goes in. Assuming the joists cross the line is the costly mistake: a partition running between two joists has nothing to screw its head plate into without noggins above the ceiling.
The door, its lining and the framed opening — three sizes
Leaf 762 × 1981 mm (2 ft 6 in × 6 ft 6 in); lining 770 × 2000 mm (30.3 × 78.7 in) inside; framed opening 840 × 2040 mm (33.1 × 80.3 in) for a 30 mm (1.2 in) lining, 5 mm (0.2 in) packing each side and 10 mm (0.4 in) over the head, starting 300 mm (12 in) from one end wall
The leaf size from the door being bought, the lining's inside size from its own instructions for that leaf, and the framed opening from the lining's inside size plus its own thickness and the packing on each side and over the head. Framing to the leaf is the classic error: the lining then has nowhere to go and the opening is rebuilt.
Stud section, centres and where the set-out starts
38 × 89 mm (1.5 × 3.5 in) CLS at 400 mm (about 16 in) centres from one end wall, an 89 mm (3.5 in) cavity
The centres are chosen so every 1200 mm board edge lands on a stud, and the set-out runs from the end wall the first board starts against. Setting out from the door instead is the usual slip: the centres come out right around the opening and every board joint misses a stud.
Board and insulation, read from the packs
15 mm (about 5/8 in) acoustic plasterboard in 2400 × 1200 mm sheets; mineral wool assumed at 6.0 m² (65 sq ft) a pack for this example
Taken off the labels of the products being bought: sheet size and thickness for the board, and the cover per pack for the wool at the thickness chosen. Borrowing the cover printed for a thermal roll or for a different thickness changes the pack count without anyone noticing.
The takeoff, in order
Each step needs something from the one before it, which is why the order is part of the answer.
Frame the partition and the door opening
- Needs
- The 3.6 m line and the 400 mm centres from the measurements, and the door as one opening. The ends are fixed to existing masonry rather than framed as corners, so no corner studs are added; nothing is ordered before this, because every later step lands on this frame.
- Produces
- 13 studs: ten across the run, including the two plugged to the end walls, and three for the door, which here are two door studs and a third length that the 840 mm head is cut from. Each stud is cut to 2.32 m from a 2.4 m length. The two field positions that fall inside the opening, at 400 and 800 mm, become short studs over the head. The calculator sets its centres at 16 in (406 mm), so its bay line differs slightly from a 400 mm set-out, but the count of ten is the same either way. Its three door studs are an allowance for American king and jack studs, and its plate line of 10.8 m assumes a double top plate; this partition takes one sole and one head plate, and the sole is cut out across the doorway once the frame stands. Noggins are not in the count.
Result13 studs of 38 × 89 mm CLS; plates are one sole and one head, 3.6 m (11.8 ft) each, not the calculator's 10.8 m (35.4 ft)
Stud CalculatorCount the plasterboard for both faces
- Needs
- The frame from step one — 3.6 by 2.4 m, studs at 400 mm so each 1200 mm sheet edge lands on one — and the 840 × 2040 mm opening its door studs frame, taken off each face. The lining is fitted at first fix, so the boards butt up to it.
- Produces
- 6 sheets of 2400 × 1200 mm: 13.9 m² of board once the doorway comes off both faces, plus a tenth, divided by one sheet. Laid out, it is the same answer: the first board on each face is cut to 800 mm, so its joint lands on the short stud over the head and the boards either side wrap the two head corners as Ls. Its 400 mm offcut finishes the far end, which keeps it to three sheets a face. Each board is cut about 10 mm short of 2400 mm so it can be lifted clear of the floor for the sealant in step five. The calculator measures a room as 2 × (length + width), so the partition goes in as a room 3.6 m long and 10 mm wide, the least the field takes, with the door entered twice, once for each face.
Result6 sheets of 2400 × 1200 mm (6 of 4 × 8 ft in US stock) for 13.9 m² (150 sq ft) of board
Drywall CalculatorScrew the first face, and count for both
- Needs
- The 6 sheets from step two and the 400 mm stud centres from step one. A screw can only go where a stud is, so the field grid is set to the stud centres rather than to a comfortable spacing.
- Produces
- 204 screws, 34 a sheet: 24 round the edge at 300 mm and 10 on the two studs inside each sheet. That grid also spaces the inner rows 400 mm along each stud, where wall boards are commonly screwed at about 300 mm, so this is the low figure — and the drywall page's flat 32 a sheet, 192, is lower still. Only the first face goes up now; the second waits for the wool.
Result204 screws, 34 a sheet at 300 mm (12 in) round the edges
Drywall Screw Count Calculator (Field + Perimeter Spacing)Fill the cavity with mineral wool
- Needs
- The frame from step one with the first face on from steps two and three, so the wool has a back to sit against, and the cavity area: 3.6 × 2.4 m less the 840 × 2040 mm opening, counted once, since the wool fills the space between the faces rather than lining each.
- Produces
- 2 packs for 6.93 m² of cavity at the assumed 6.0 m² a pack, with the calculator's default allowance. Each bay is cut to fill snugly rather than packed hard against the boards, though over-compression matters more on a decoupled wall than on this one, where both faces are screwed to the same studs. Anything heavy that will hang on this wall gets its noggin or ground now, before the second face hides the bay.
Result2 packs of mineral wool for 6.93 m² (74.6 sq ft) of cavity, at an assumed 6.0 m² (65 sq ft) a pack
Mineral Wool Insulation Batt CalculatorBoard the second face and seal the perimeter
- Needs
- Both faces boarded from steps two and three, each held a few millimetres off the floor, the ceiling and the end walls, and the doorway from step one, where the floor joint stops: 11.16 m of board edge a face, 22.32 m for the two.
- Produces
- 0.80 L of acoustic sealant for a 6 mm square bead round both faces. The figure is the bead and nothing else: the cartridge count follows from the size printed on the tube, rounded up, and a nozzle cut one size large puts far more into the same run. It is done now because the floor joint disappears behind skirting in step ten and the ceiling and end joints under scrim in step six. The gap between the lining and the door studs is sealed too, but it belongs to the lining and is not in this figure.
Result0.80 L (27 US fl oz) of acoustic sealant for 22.3 m (73 ft) of 6 mm (1/4 in) bead
Acoustic Sealant Bead Volume CalculatorScrim the joints and the angles
- Needs
- The 13.9 m² of board and its 2.4 m sheet length from step two, and the angles the partition makes with the ceiling and the two end walls — 8.4 m a face, 16.8 m in all — each sealed behind in step five.
- Produces
- 37.6 m of scrim, comfortably inside a single roll. The flat-joint part is a rate for a field of sheets with a joint on every side. These sheets stand floor to ceiling in one row, so their tops are the ceiling angle and their feet sit behind skirting, and the flat joints are really only the vertical ones — the figure reads high, and the purchase does not change.
Result37.6 m (123 ft) of scrim tape, one roll
Drywall Joint Tape CalculatorStop the plaster at the door lining
- Needs
- The lining edges round the opening from step one, the one place on this wall where plaster ends against another material. The partition meets masonry at both ends and turns no external corner, so it takes no angle bead at all.
- Produces
- 4 lengths of 3 m thin-coat stop bead for the four jamb edges, two a face at 2.04 m each. The jambs use 8.16 m of the 12 m bought, and on this wall the rest is not waste: each jamb leaves 0.96 m and each head needs 0.84 m, so two of the four offcuts become the heads. The calculator does not assume that, since offcuts and short runs rarely match; here they do. A plasterer who skims straight to the lining and lets the architrave cover the edge leaves this step out.
Result4 lengths of 3 m (9.8 ft) stop bead, the two heads cut from the offcuts
Plaster Angle and Stop Bead CalculatorSkim both faces
- Needs
- The 13.9 m² of board from step two, scrimmed in step six and edged with bead in step seven, and the 2 mm finished thickness that new, flat board takes.
- Produces
- 40.0 kg of finish plaster: 34.75 kg on the wall plus the calculator's standard allowance for what goes off in the bucket, which buys two 25 kg bags. Split by face it is the same purchase: each face takes 17.4 kg, 20.0 kg with the allowance, so one 25 kg bag a face with a little in hand.
Result40.0 kg (88.1 lb) of finish plaster: two 25 kg bags (two 50 lb bags in US stock)
Skim Coat Plaster CalculatorArchitrave the door on both faces
- Needs
- The lining fitted at first fix in the opening from step one, entered at its inside size of 770 × 2000 mm rather than the 840 × 2040 mm the studs frame, once for each face, with the skim from step eight dry against it.
- Produces
- The calculator works in feet, so the pinned figure is 34.4 ft; its page shows a metric visitor 10.5 m with the mitre allowance, or 5 lengths of 2.1 m. A cutting list agrees. A leg is the lining height plus a 6 mm margin plus the 69 mm architrave width at the mitre, a little under 2.1 m, so each of the four legs takes a length and the two heads, about 0.92 m each, share the fifth. An architrave set of two legs and a head per face buys the same.
Result10.5 m (34.4 ft) of architrave with the mitre allowance: 5 lengths of 2.1 m
Door & Window Casing CalculatorRun the skirting to the architraves
- Needs
- Both faces from step two, the architraves from step nine that the skirting stops against, and the sealed floor joint from step five that it covers. The partition goes in as a room 3.6 m long and 10 mm wide again, with a doorway for each face.
- Produces
- 19.6 ft as computed, again in feet, which the page turns into 6.0 m with the cutting allowance, or 2 lengths of 3 m. The calculator takes a flat 0.9 m off for each doorway, close to the width across these architraves' outer edges. Wall by wall it is the same count: each face has one long piece a little over 2.4 m, too long for a 2.4 m length without a joint, and a short piece beside the door that comes from the same 3 m length.
Result6.0 m (19.6 ft) of skirting with the cutting allowance: 2 lengths of 3 m
Baseboard & Trim Calculator
The figures
| Step | Calculator | Figure |
|---|---|---|
| Frame the partition and the door opening | Stud Calculator | 13 studs of 38 × 89 mm CLS; plates are one sole and one head, 3.6 m (11.8 ft) each, not the calculator's 10.8 m (35.4 ft) |
| Count the plasterboard for both faces | Drywall Calculator | 6 sheets of 2400 × 1200 mm (6 of 4 × 8 ft in US stock) for 13.9 m² (150 sq ft) of board |
| Screw the first face, and count for both | Drywall Screw Count Calculator (Field + Perimeter Spacing) | 204 screws, 34 a sheet at 300 mm (12 in) round the edges |
| Fill the cavity with mineral wool | Mineral Wool Insulation Batt Calculator | 2 packs of mineral wool for 6.93 m² (74.6 sq ft) of cavity, at an assumed 6.0 m² (65 sq ft) a pack |
| Board the second face and seal the perimeter | Acoustic Sealant Bead Volume Calculator | 0.80 L (27 US fl oz) of acoustic sealant for 22.3 m (73 ft) of 6 mm (1/4 in) bead |
| Scrim the joints and the angles | Drywall Joint Tape Calculator | 37.6 m (123 ft) of scrim tape, one roll |
| Stop the plaster at the door lining | Plaster Angle and Stop Bead Calculator | 4 lengths of 3 m (9.8 ft) stop bead, the two heads cut from the offcuts |
| Skim both faces | Skim Coat Plaster Calculator | 40.0 kg (88.1 lb) of finish plaster: two 25 kg bags (two 50 lb bags in US stock) |
| Architrave the door on both faces | Door & Window Casing Calculator | 10.5 m (34.4 ft) of architrave with the mitre allowance: 5 lengths of 2.1 m |
| Run the skirting to the architraves | Baseboard & Trim Calculator | 6.0 m (19.6 ft) of skirting with the cutting allowance: 2 lengths of 3 m |
The waste factors, and why these ends of the ranges
| Material | Applied | Why |
|---|---|---|
| Plasterboard | The calculator's standard tenth, which the whole-sheet rounding then overrides | 13.9 m² with 10% added is 5.3 sheets, and every allowance from 5% to 24% still buys 6; only the calculator's 25% ceiling tips it to 7. The count is set by the board module — three sheets a face — and the doorway cut out of those sheets is the real waste, whatever percentage is typed. |
| Mineral wool | The calculator's small default, with the stud faces left in the area | Wool is cut to the bay and the offcut from one bay starts the next, so cutting loses little; the 5% covers the pieces round the door head. The area still includes every stud, a 38 mm face at 400 mm centres or near a tenth of the wall, and both plates, none of which the wool fills. The timber left in the area already outweighs the allowance, so the count leans over before the whole-pack rounding. |
| Finish plaster | The calculator's standard allowance, deliberately not raised for a small wall | The 15% covers plaster that sets in the bucket. On 13.9 m² the bag rounding matters more: 34.75 kg goes on the wall and two bags hold 50 kg. Any allowance up to 43% still buys two bags, so raising it for a small job, as the calculator's help suggests, changes nothing here — the second bag already carries it. |
| Stop bead | Nothing on top: the two heads come out of what the jambs leave | Each jamb takes one 3 m length and leaves 0.96 m; each head needs 0.84 m. Four lengths is already a count of whole sticks, and two of its offcuts are the heads, so an allowance on top would buy bead for runs this wall does not have. |
| Architrave and skirting | The calculators' tenth, then checked against a cutting list | Both calculators divide a run by a stock length, which says nothing about which piece comes from which length. Here they agree with the bench — four legs and a shared length for the heads, one 3 m length a face for the skirting — but over half of the architrave's 10% is already spent on the margin and the width each leg runs past the lining at its mitre. |
| Acoustic sealant | None in the figure; whole cartridges above it | The calculator returns the volume of the bead and has no allowance input. The dead length a gun cannot push out of each cartridge and a nozzle cut a size too big both come on top, so the order is whole cartridges rounded up from 0.80 L, never at it. |
Where this estimate is most likely to be wrong
Timber for the frame
usually underThe stud count covers studs at their centres and three for the door, the third giving the head. It does not include a row of noggins or the grounds for a wall-hung television or shelves, and the site has no calculator for either. The plate line errs the other way, since it assumes a double top plate this partition does not have, and whether that spare length covers the noggins depends on the drawing rather than on the count.
Narrow it by: Drawing the frame elevation with the opening, the head, the noggin line and every fixing ground, then counting lengths off the drawing rather than off the run.
Plasterboard screws
usually underThe screw page lays its field rows on the 400 mm stud centres, which is right across a sheet and generous along each stud, where wall boards are commonly fixed at about 300 mm. Sheets cut round the doorway also gain screws along their cut edges that a whole-sheet pattern never counts.
Narrow it by: Taking the along-stud spacing from the board maker's fixing guide, and counting screws per stud line on the elevation rather than per sheet.
Mineral wool packs
usually overThe cavity is taken as the wall less the doorway, with every stud, both plates and the door head still in it, and the count is then rounded up to whole packs. Both push the same way. The one thing that can reverse it is the pack itself: the cover here is an assumed figure, and a smaller one on the label bought changes the count.
Narrow it by: Reading the cover off the pack actually on the van, and taking the stud and plate faces out of the area before the rounding.
Flat-joint scrim
usually overThe tape page counts flat joints as a field of sheets with a joint on every side. A partition hung as one row of full-height sheets has only its vertical joints; the tops meet the ceiling angle, which is counted separately, and the feet vanish behind skirting. The figure is high on that account, and the error stays inside the same roll.
Narrow it by: Counting the vertical joints off the board layout on each face and adding the measured angles, rather than applying an area rate to a single-row wall.
Sound performance rather than material
usually underThe quantities buy an insulated, sealed panel, but what a listener hears is set by the weakest path through or round it. A standard door with an undercut and no seals, a socket box in each face of the same bay, or a floor joint where the bead was skipped behind the skirting will each pass more than the rest of the wall, and nothing on this page measures them.
Narrow it by: Choosing a solid leaf with perimeter seals at the same time as the wool, offsetting any back-to-back sockets by a stud bay, and checking the sealed joints before trim covers them.
Tools this job needs
Frequently asked questions
- How many studs do I need for a stud wall with a door?
- For a 3.6 m (11.8 ft) partition at 400 mm (about 16 in) centres, 13: ten across the run, including the two fixed to the end walls, and three for the door, two door studs and a third length for the head. Each is cut to 2.32 m (7 ft 7 in) from a 2.4 m (7.9 ft) length under a 2.4 m (7.9 ft) ceiling. Add a sole plate and a head plate, 3.6 m (11.8 ft) each, plus any noggins, which the count leaves out.
- How many sheets of plasterboard do I need for a stud wall?
- Both faces of a 3.6 × 2.4 m (11.8 × 7.9 ft) partition, less an 840 × 2040 mm (33 × 80 in) doorway on each, come to 13.9 m² (150 sq ft) of board. With a tenth added and divided by one 2400 × 1200 mm sheet, that is 6 sheets, which matches a layout of three sheets a face with the first cut to 800 mm (31.5 in). They take about 204 screws at 300 mm (12 in) round each sheet's edges.
- How do you soundproof a stud wall?
- Add mass, fill the cavity and close the gaps. This wall has 15 mm (about 5/8 in) acoustic plasterboard each face, 2 packs of mineral wool for 6.93 m² (74.6 sq ft) of cavity at an assumed 6.0 m² (65 sq ft) each, and 0.80 L (27 US fl oz) of sealant round 22.3 m (73 ft) of board edge. The door sets the limit: a gap under it can pass more sound than the wall around it, so its leaf and seals matter as much as the wool.