Woodwork
Window frame paintable area
- where
- frame area per side (m²)
- window frame width (m)
- window frame height (m)
- number of panes
- visible pane width (m)
- visible pane height (m)
- total frame area (m²)
- sides painted
Explain this equation
Works out the paintable area of a window frame by taking the glass away from the overall size.
The overall frame is width times height. Each pane of glass is its visible width times height, and all panes are taken off. What is left is the timber to paint on one side; times the sides painted gives the total.
Area of the outer rectangle minus the inner rectangles.
Sense check: a 1.2 × 1.2 m window with two 0.5 × 1.0 m panes has about 0.44 m² of frame per side.
Watch out: sashes, glazing bars and rebates add area that this flat measurement misses; allow extra on multi-pane windows.
Works out the painted timber on a window by taking the glass away from the overall frame size.
Enter your values to see the result.
Good to know
NRM 2 measures glazed surfaces as the area actually painted, irrespective of pane size. Add the sill and any reveal linings separately with the skirting calculator (length × girth). Small-paned sashes are slow to cut in, so price the labour by time rather than area.
Common mistake
Pricing a window as its full opening area, which can double the paint and hide the real cost, the cutting-in time.
Limits
Rectangular panes of equal size. For mixed panes, run once per pane size with Np for each and add.
Sources
- RICS NRM 2 Detailed measurement for building works, Work section 29 Decoration (area or girth measured is that covered; frames measured edge to edge; ≤ 300 mm and > 300 mm girth; radiators by type)
- Geometry: rectangle and cylinder surface areas, prism volumes
Results are calculations from the published methods and figures shown, and depend on the data you enter. Coverage depends on the product, surface and application. Always follow the paint and wallcovering manufacturers’ data sheets and BS 6150 / BS 8000-12. Check prices and VAT with your own records and HMRC.