Finishes quantity takeoff: plaster, paint, tiling and waterproofing in wet rooms
A finishes quantity takeoff is one of the places where mistakes come easily, because finishes are usually not modelled as separate elements. Plaster, paint, wall tiling and waterproofing are calculated from the faces of the walls and ceilings and from the rooms, and then checked against each other. When the checks agree, the chance of a mistake is smaller, and the quantities are easier to explain to a contractor.
Finishes quantity takeoff: where the quantities come from
There are two main routes: the wall and ceiling faces from the model, and the room boundaries with the net height. Roughly, the finished wall area of a room is its perimeter times the net height, minus openings. In the bill of quantities (BOQ) itself, deductions and additions follow the methods of measurement of the project. The difference between the two is explained on the physical quantity versus BOQ quantity page.
In the example the net height is 3.10 m minus a 22 cm slab, that is 2.88 m, and the same height is used for the partitions, the plaster and the paint. On a real project, check the height of each item against the details, for example under a suspended ceiling. When there is no model, the same calculation is done from the drawings and the room schedules.
Plaster: two items
In the example, the tiled walls have cement plaster under the tiles, and the other walls and the ceilings have gypsum plaster. So the gypsum plaster on the walls is the wall faces minus the tiling, and the cement plaster equals the tiled area. On every project, the substrate for the tiling and the type of plaster follow the specification and the details: on some projects the tiles are fixed directly to blockwork, to concrete or to plasterboard.
Paint and plasterboard ceilings
Paint: a consistency check against plaster and tiling
In the example, the paint on the walls equals the plaster on the walls minus the tiling, that is 964.80 m². This is a useful consistency check, and any departure from it is explained by the specification, for example plasterboard walls or painted concrete with no plaster. An average ratio of paint to plaster taken from several projects says little, because the tiled area changes from building to building with the number of wet rooms.
Plasterboard ceilings: out of the plaster, back into the paint
In the example, the slab above a suspended plasterboard ceiling is not plastered, so that area comes off the ceiling plaster: 380 minus 85 m², that is 295 m². The plasterboard is painted, so the same area goes back into the paint quantity. On every project, check in the specification what treatment the slab above the suspended ceiling receives.
Wet rooms: waterproofing is measured separately from tiling
A wet room is usually identified by its fixtures, such as a bath, a shower, a WC or a floor drain, but the definition and the extent of the waterproofing are checked against the specification of the project's waterproofing consultant. In the example, the tiling and the wall waterproofing reach different heights, and each is kept in a separate field, so a change in one does not change the other.
Mechanical ventilation is usually required in wet rooms without a window, and its quantity is taken from the consultant's design and from the consultant's own BOQ. A count by room can serve as a reasonableness check, as a note to the consultant.
For illustration only. The heights and numbers on this page come from a synthetic example. On every project they are set by the specification, the details, the waterproofing consultant's specification and the applicable standards.
Aluminium and joinery: the schedule against the model
Windows and doors are usually counted from the architect's schedule. The model gives the location on the floor and the opening to deduct from the blockwork and the plaster. Each item is cross-checked in both directions: an item that is in the schedule but not in the model stays in the BOQ and is marked for completion, and an item that is in the model but not in the schedule goes to the designer as a question. In the example there are 8 windows of type W-4 in the schedule and 8 instances in the model.
Example: a typical floor in ten rows
Clicking a row highlights in the model what was measured in it and shows the formula. The model shows one flat, and the quantities are for a floor of four flats.
| Item | Description | Unit | Quantity | Check |
|---|---|---|---|---|
| 04.010 | Block partitions 10 cm thick, net of door openings | m² | 363.60 | Net height 2.88 |
| 05.010 | Waterproofing of floors and walls in wet rooms | m² | 102.00 | Waterproofing ≠ tiling |
| 10.010 | Wall tiling: bathrooms up to 2.40 m, guest WCs up to 1.20 m | m² | 175.20 | Perimeter times height |
| 09.010 | Cement plaster (base coat) under the tiling | m² | 175.20 | Equals tiling |
| 09.020 | Gypsum plaster on walls, excluding the tiled areas | m² | 964.80 | Faces − tiling |
| 09.030 | Gypsum plaster on ceilings, excluding the suspended ceiling area | m² | 295.00 | Ceilings − suspended |
| 22.010 | Suspended plasterboard ceilings | m² | 85.00 | Back into paint |
| 11.010 | Acrylic paint on walls and ceilings, including the plasterboard ceilings | m² | 1,344.80 | Plaster + plasterboard |
| 12.010 | Aluminium window type W-4, 160/140 cm | nr | 8 | Schedule 8 · model 8 |
| 10.050 | Wall tiling in kitchens | m² | Missing | Missing |
| Check | Formula and result | Conclusion |
|---|---|---|
| Wall paint against wall plaster minus tiling | =ROUND((175.20+964.80)-175.20,2) = 964.80 | In the example, equal to the gypsum plaster on walls |
| Plasterboard ceilings: out of the plaster, back into the paint | =ROUND(295.00+85.00,2) = 380.00 | Equal to the ceiling area of the flats |
| Mechanical ventilation: wet rooms without a window (reasonableness check) | =4 | Four guest WCs; the quantity itself is in the consultant's BOQ |
| Type W-4 windows: schedule against model | =8-8 = 0 | No item in the schedule without an instance in the model |
The kitchen tiling row stays "missing" until the tiling specification arrives. A quantity that looks reasonable without a specification is a guess, and a guess in the BOQ can later turn into a variation.
A quantity surveyor who comes from the field, an engineer or a registered building technician who worked on site, like Yaakov Avital, reads the specification and the drawings together, in a finishes quantity takeoff too. For example, a consultant's report calls for a lowered ceiling in every room, while the architectural drawing marks it in only some of them. Or the finishes specification lists layers on the walls of the protected room (mamad), the reinforced safe room in every Israeli flat, and the drawings do not show where they are applied. Measuring only what is marked puts only what is marked into the BOQ. A professional check flags the gap as a question to the designer, and the designer decides. More on this on the professional BOQ page.
In a finishes quantity takeoff, a quantity surveyor also checks the finishes schedule against the drawings, because quite often a room appears on a drawing without its finish being defined.
Frequently asked questions
Why not calculate the paint as a factor of the plaster?
Because the ratio depends on the tiled area. Checking plaster minus tiling gives the quantity for this building, not an average of other buildings.
Do plasterboard ceilings go in the plasterboard chapter or in paint?
Usually in both, as different items: the ceiling itself in the plasterboard chapter, and its painting in the paint chapter.
What do you do when there is no finishes specification yet?
Mark the row as missing and state what is missing. When the specification arrives, complete the quantity and mark what changed.
Does this work for a private house too?
The principles are similar. For a private house the BOQ is shorter, and you can read about it on the BOQ for a private house page. More about the role on the quantity surveyor for construction projects page.
Have a project? Tell me briefly what the project is and what already exists. When the project is a good fit, I usually reply with focused questions and a written quote.
Contact me for a quote* Created with AI for marketing, for illustration only. Not reviewed by Yaakov Avital and not professional advice. Every project must be checked on its own by a professional quantity surveyor and an engineer.