meters
meters
Walls36.5 m²
Ceiling14.4 m²
Room total50.9 m²
Bedroom 1
CeilingWalls
Home / Plasterboard calculator
How much plaster does a new home need, and what will it cost?
Add your rooms, enter the floor size and ceiling height, and this works out the total square metres of wall and ceiling lining your build needs, then estimates the supply and install cost. Built for a house at frame stage, room by room, the way a plasterer actually measures it.
Three rules before you start
Do not deduct windows, doorways or skylights
Measure the room as though it had none. Board is hung across the opening and cut out afterwards, the offcut is usually waste, and the reveals still have to be set. Deducting them makes the estimate too low rather than more accurate.
Measure the floor, not the walls
Enter the floor length and width. The tool works the wall area out from the perimeter, so you never have to measure a wall.
Add only the rooms being lined
If the garage is being left as bare frame, leave it out. A garage sharing a wall with the house usually needs a fire rated system rather than a flat rate, so mention it when you send your plans.
Room by room
Add every room you want lined. This is the accurate version, and it is what to send through with your plans.
These are estimates only
This tool exists to help you budget a project, not to price one. Accurate costs are only ever stated on a written quote.
How this estimate is worked out
Every number the tool produces comes from the two formulas below. Nothing is hidden and nothing is fudged, so you can check it by hand on any room in your plans.
Ceiling area = length × width
Wall area = 2 × (length + width) × ceiling height
Room total = ceiling area + wall area
Wall area = 2 × (length + width) × ceiling height
Room total = ceiling area + wall area
Worked through on a 4.0m by 3.6m bedroom with 2.7m ceilings: the ceiling is 4.0 × 3.6 = 14.4 m². The perimeter is 2 × (4.0 + 3.6) = 15.2m, so the walls are 15.2 × 2.7 = 41.04 m². That bedroom needs 55.44 m² of lining, which is 18 sheets once wastage is allowed: 14 wall sheets at 2700 × 1200 and 4 ceiling sheets at 3600 × 1200. Most people are surprised it is that much, because the floor is only 14.4 m² and the walls are nearly three times it.
Why both sides of an internal wall are counted
Add a bedroom and the hallway next to it and the wall between them gets measured twice, once from each room. That is correct, not double counting. A plasterer sheets, sets and charges for both faces of an internal wall, because both faces are separate work. External walls are only counted once, because the outside face is not a room and never appears in the calculation.
This is why plaster is quoted by the square metre of lining, not by the square metre of floor. A long thin hallway has very little floor and an enormous amount of wall, and it is one of the most expensive spaces per square metre of floor in the whole house.
Why openings are not deducted
A 900mm doorway does not save a plasterer 900mm of board. The sheet is hung across the opening and the hole is cut out afterwards, and the piece that comes out is usually too small to use anywhere else. The head and jambs still need edge treatment. Deducting openings would understate a real quote by roughly five to eight per cent on a typical house.
Why bathrooms, ensuites and laundries cost more
Wet areas are lined with water resistant board rather than standard plasterboard, and the board itself is roughly double the price. Under the National Construction Code, Housing Provisions Part 10.2, shower walls must be waterproof to not less than 1800mm above the floor substrate, and junctions within the shower must be waterproof for not less than 40mm either side. Water resistant plasterboard is a permitted substrate under clause 10.2.9, but it is water resistant, not waterproof. The waterproof membrane goes over it, to AS 3740. Wet areas are also small, fiddly and slow, with more cuts per square metre than any other room in the house.
What the estimate includes
Typical new home plaster quantities
If you have not got dimensions to hand yet, these are the figures a new build usually lands on. Areas are wall and ceiling lining combined, measured the same way the tool measures, with no deductions for openings.
| House | Floor area on plan | Ceiling lining | Wall lining | Total lining | Sheets, 2700 × 1200 |
|---|---|---|---|---|---|
| 2 bed unit, 1 bath | 75 m² | 62 m² | 220 m² | 282 m² | 92 |
| 3 bed single storey, 2 bath | 125 m² | 106 m² | 369 m² | 475 m² | 155 |
| 4 bed single storey, 2 bath, garage | 190 m² | 165 m² | 494 m² | 658 m² | 212 |
| 4 bed two storey, 2.5 bath, garage | 220 m² | 190 m² | 588 m² | 778 m² | 251 |
| 5 bed two storey, 3 bath, double garage | 270 m² | 234 m² | 699 m² | 933 m² | 301 |
The rule of thumb that falls out of that table: total lining runs about three and a half to three and three quarter times the floor area shown on your plans at 2.7m ceilings. Smaller homes sit at the top of that range and larger homes at the bottom, because a big living room encloses far more floor per metre of wall than a small bedroom does.
Note that the ceiling lining figure is always less than the floor area on the plan. Plan floor area is measured to the outside of the external walls and includes the thickness of every wall in the house, but the ceiling that actually gets sheeted is only the internal area of the rooms. On a typical build that is about 86 per cent of the plan figure. It is a small detail that trips up a lot of budgets, because people multiply the plan area by a ceiling rate and wonder why the quote came in under.
Reference
Sheet sizes, coverage and weight
Australian plasterboard is sold in 1200mm widths as standard, in lengths from 2400mm up to 6000mm. On a new build the wall sheets are chosen to match the ceiling height so the board runs floor to ceiling in one piece with no horizontal joint, which is why the tool picks the sheet length from the height you enter.
| Sheet size | Coverage | Wall board | Ceiling board | Typical use |
|---|---|---|---|---|
| 2400 × 1200 | 2.88 m² | 16.4 kg | 17.6 kg | 2.4m ceilings |
| 2700 × 1200 | 3.24 m² | 18.5 kg | 19.8 kg | 2.7m ceilings, the current standard |
| 3000 × 1200 | 3.60 m² | 20.5 kg | 22.0 kg | 3.0m ceilings, feature rooms |
| 3600 × 1200 | 4.32 m² | 24.6 kg | 26.4 kg | Ceilings, fewer joints |
| 3600 × 1350 | 4.86 m² | 27.7 kg | 29.6 kg | Large ceilings |
| 4200 × 1200 | 5.04 m² | 28.7 kg | 30.7 kg | Long runs, raked ceilings |
| 4800 × 1200 | 5.76 m² | 32.8 kg | 35.1 kg | Commercial, long corridors |
| 6000 × 1200 | 7.20 m² | 41.0 kg | 43.9 kg | Commercial only, team lift |
Weights are calculated from the published board mass: 5.7 kg per square metre for 10mm standard wall board and 6.1 kg per square metre for 10mm span rated ceiling board. Anything over about 30kg is a genuine two person lift, which is worth knowing before a delivery lands on a driveway with nobody home.
Allowances
Wastage, and why the sheet count is higher than the area
Dividing the lining area by the sheet coverage gives the theoretical minimum, and no house has ever been built with the theoretical minimum. Cuts, offcuts, damaged corners, openings and the last piece of every run all add up.
| Surface | Allowance | Why |
|---|---|---|
| Walls, simple rectangular rooms | 10% | Openings cut from full sheets, end of run offcuts |
| Ceilings | 15% | Sheets must land on joists, so the cut is set by the frame |
| Wet areas | 15% | Small rooms, many cuts, fixtures and niches |
| Hallways and stairwells | 15% | Narrow, many short runs, high offcut rate |
No Australian plasterboard manufacturer publishes a wastage figure, so these are trade allowances rather than a manufacturer specification. They sit at the conservative end of what the trade uses, because running out of board mid ceiling costs more than the sheet did.
Frame spacing, and the number most people get wrong
Board thickness dictates how far apart the frame can be. Get this wrong and the ceiling sags between the joists, which is the single most common reason a ceiling has to be re-sheeted a few years after it was built.
| Application | Board | Maximum centres |
|---|---|---|
| Ceiling | 10mm standard plasterboard | 450mm |
| Ceiling | 10mm span rated ceiling board | 600mm |
| Ceiling | 13mm plasterboard | 600mm |
| Ceiling, high humidity | Any 10mm or 13mm | 450mm |
| External ceiling or soffit | Any | 450mm |
| Wall, wind classes N1 to N6, C1, C2 | 10mm, sheeted horizontally | 600mm |
| Wall, wind classes C3, C4 | 10mm, sheeted horizontally | 450mm |
Drawn from the manufacturers' published installation tables. Wind classification comes from AS 4055 and is set for your site rather than chosen. If a builder specifies 600mm ceiling joists, the ceiling needs span rated 10mm board or 13mm board, not standard 10mm.
Questions people ask
How many sheets of plasterboard does a new house need?
A 4 bedroom single storey home of about 190 square metres with 2.7m ceilings needs roughly 658 square metres of lining, which is about 212 sheets once a 10 per cent wall and 15 per cent ceiling wastage allowance is included. A 3 bedroom home of about 125 square metres needs closer to 155 sheets, and a 5 bedroom two storey around 301 sheets.
Those figures assume a lined garage. Take the garage out of a single storey home and you drop roughly 30 sheets, because a double garage is one of the largest single spaces in the house.
How much does it cost to plaster a new home in Australia?
Supply and install, set to a Level 4 finish with standard cove cornice, generally lands between the mid thirties and the mid fifties per square metre of lining for walls, a little higher for ceilings because all of it is worked overhead, and higher again in wet areas because the board costs about double. Put your own rooms through the tool above for a figure based on your actual plan rather than an average.
Because plaster is priced on lining area and not floor area, a quick sanity check on any quote is to multiply the floor area on your plans by three and a half, then by the rate per square metre you have been given. If the answer is nowhere near the quote, one of you is measuring something different, and it is worth asking which.
Why is the wall area so much bigger than the floor area?
Because walls go up and floors do not. A 4.0m by 3.6m bedroom has 14.4 square metres of floor and 41.04 square metres of wall at 2.7m, so the walls are 2.85 times the floor.
Narrow rooms are far worse. A 6.0m by 1.2m hallway has 7.2 square metres of floor and 38.88 square metres of wall, which is 5.4 times the floor. That is why hallways cost so much more than people expect, and why a plasterer will never quote off floor area.
Should I deduct doors and windows from my measurements?
No. Enter every room as though it were a sealed box. The board is hung straight across an opening and the hole is cut out afterwards, so the sheet is still consumed, and the piece that comes out is usually too small to use anywhere else. The reveals around the opening still need setting.
On a typical house, deducting openings understates the real cost by about five to eight per cent, which is the wrong direction for a budgeting tool to be wrong in.
Why are both sides of an internal wall counted?
Because both sides get sheeted, set and charged. Measuring room by room counts a shared wall once from each side, and that is correct rather than double counting: each face is separate work with its own board, its own joints and its own finish.
External walls are counted once, because the outside face is not a room and never enters the calculation. This is also why plaster is quoted by the square metre of lining rather than by the square metre of floor.
Do I include the garage?
Only if it is being lined. Garages vary more than any other space in a new build: some are fully lined walls and ceiling, some get the ceiling only, and some are left as bare frame.
If your garage shares a wall with the house it will usually need a fire rated system rather than standard board, and that is priced on the specified build up rather than on a flat rate per square metre. Leave the garage out of the tool and mention it when you send your plans.
Why do bathrooms and laundries cost more per square metre?
Three reasons stack up. The board is water resistant rather than standard and costs roughly double. The rooms are small, so the number of cuts per square metre is far higher than in a bedroom. And the work is slower around fixtures, niches and shower recesses.
Under the National Construction Code, Housing Provisions Part 10.2, shower walls must be waterproof to not less than 1800mm above the floor substrate, and junctions within the shower must be waterproof for not less than 40mm either side. Water resistant plasterboard is a permitted substrate, but it is water resistant rather than waterproof, so a membrane to AS 3740 goes over it before tiling.
Does the estimate include cornice?
Yes. Standard cove cornice supplied and installed is in the rate. Cove is the default in Australian housing and comes in 55mm, 75mm and 90mm profiles in 3000, 3600, 4800 and 5400mm lengths.
What is not in the rate is square set, which has no cornice at all and instead needs a Level 5 finish at the wall and ceiling junction, and ornate or stepped profiles. Square set looks cleaner, costs noticeably more, and is more prone to hairline cracking as the frame moves.
What is a Level 4 finish, and is it good enough?
Levels of finish are defined in AS/NZS 2589, the Australian standard for gypsum lining application and finishing. Level 4 is the generally accepted level for domestic construction, with joints finished in a three coat system.
Level 5 adds a skim over the entire surface and is used where critical lighting will rake across a wall, for square set junctions, and for dark or gloss paint finishes. Most new homes are Level 4 and look perfectly good. If you are specifying large glazed areas that will wash light along a wall, ask about Level 5 for those walls only.
How accurate is this estimate?
The area calculation is exact for the dimensions you enter, because it is arithmetic. The cost is deliberately shown as a range of about fifteen per cent either side, because the things that move a real plastering price are not in your room dimensions: frame accuracy, ceiling design, stair voids, raked and bulkhead ceilings, site access, storey height and the level of finish specified.
Use it to know whether you are budgeting twenty thousand or forty. Use a written quote to know the number.
When in the build should I get a plastering quote?
Send plans as early as you like for budgeting, but the quote that matters is measured off the final working drawings once the ceiling design is settled.
Plaster goes on after the frame is up, the roof is on, and the electrical and plumbing rough in is complete and inspected. Booking a plasterer only once the frame is standing is how builds lose weeks, because a good crew is usually committed several weeks out.
Turn the estimate into a fixed quote
Send your floor plans and you will get a written quote measured off the drawings, not an estimate. All materials supplied, and the owner on site with the crew.