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Internal Plaster Calculator

Internal plaster = room perimeters × height − openings − tiled skirting − dado tiling. 120 m of room perimeter at 3 m is 360 m²; less 40 m² of openings, 10 m² of skirting and 42 m² of kitchen and bathroom tiling, 268 m² remains: 16.8 bags of cement at 12 mm, 1:6.

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Behind this panel: an example with the default sizes.

Inputs

Results update as you type.

Rooms
m
m
m²
Tiled areas (not plastered)
mm
m
m
Plaster
mm
Wall with skirting and dado3 mdadoPlaster 268.0 m²plasteredtiled: skirting and dadomyconstructioncalculator.com
Diagram updates as you type.

Results

Check the working before you order.

Internal plaster area
268.0m²
Gross wall area360.0 m²
Deducted for skirting and dado52.0 m²
Cement (50 kg bags)16.8 bags (840 kg)
Sand3.50 m³
Wet plaster3.216 m³

Some specifications still plaster behind dado tiles as a flat base; if so, set the dado length to 0.

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Working
  1. Gross = perimeter × height = 360.0 m²
  2. Less openings 40.0 m², skirting 10.0 m², dado tiling 42.0 m²
  3. Net = 268.0 m² × 12 mm = 3.216 m³ wet → cement 16.80 bags
Results are estimates for planning and material ordering only. They are not a substitute for structural design or approval by a qualified engineer. Read the full disclaimer.
Formula


Gross      = Σ room perimeters × height
Skirting   = (perimeter − dado length) × skirting height
Dado       = dado length × dado height
Net        = gross − openings − skirting − dado


Worked Example


120 m of room perimeter, 3 m high, 40 m² openings, 100 mm tiled skirting, 20 m of 2.1 m high dado tiling, 12 mm 1:6:


    

  1. Gross = 360 m²
    2. 

  2. Skirting = (120 − 20) × 0.1 = 10 m²; dado = 20 × 2.1 = 42 m²
    3. 

  3. Net = 360 − 40 − 10 − 42 = 268 m²
    4. 

  4. Cement ≈ 16.8 bags, sand ≈ 3.5 m³
    5. 



Typical Internal Plaster Thickness






Background
Thickness






Brick / block, normal
12 mm




Rough or uneven masonry
15 mm




Smooth concrete
6–10 mm






Frequently Asked Questions
What mix is used for internal plaster?
Commonly 1:6 (or 1:5) cement-sand, 12 mm thick on brick or block. It is leaner than external plaster because it is not exposed to rain.
Should I deduct tiled areas from plaster?
If tiles are fixed directly to the blockwork or on a separate backing coat, deduct them. Many specifications still plaster behind wall tiles as a flat base (then don)'t.
How do I measure room perimeters?
Add the inside lengths of all walls in each room. A 4 × 3 m room has a 14 m perimeter.
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