Made-to-measure window sills
Most window sills can be ordered in standard depths. They are made to measure where the standard does not fit – for corner windows, the deep reveals of old houses, cornices or finishing a plinth.
- Sheet
- Made-to-measure sills
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- Sources
- 3 items
- Type
- information guide
When a made-to-measure sill is needed
| Situation | What is non-standard |
|---|---|
| old houses with thick walls | depth beyond the standard range, need for a stiffer material |
| corner window | two sills with a corner joint, an accurately cut corner |
| French window, balcony door | threshold profile, low height, connection to a terrace |
| historic facade with a cornice | cornice flashing with a fall and the facade’s profile |
| plinth set-back | sill-type drip over the plinth |
| curved or splayed reveals | shape taken from a template |
How to specify it
A made-to-measure sill is specified the same way as any made-to-measure flashing: a dimensioned cross-section, fold angles, material, thickness, colour, lengths and quantities, and the visible face. In addition:
- measure the depth following the rule in How to measure a window sill – reveal + ~10 mm under the frame + 30–40 mm projection,
- for a corner, state the angle (90° is not always 90°) and which piece laps over which,
- for depths over 300 mm, ask about stiffening or a thicker material,
- if the sill is set into the render, allow for the extra length at both ends (ZOFI: at least 17.5 mm per end).
Cornices and wide flashings
Wide sills and cornices behave like parapet copings: they need a fall, a backing board and limited piece lengths. For parapets PREFA gives pieces of up to 3 m for a girth of up to 500 mm, and up to 1 m for 600–800 mm. Details: Parapet coping.
Put the finished specification into the enquiry builder.
Technical sources
The sources this sheet draws on. We checked prices and values from standards on the date shown; for prices, whatever the source currently states always applies. Sources marked “in Slovak” or “in Czech” are only available in that language.
| Item | Source | Published by | Version / date | Checked |
|---|---|---|---|---|
| 01 | Measuring a window sill correctly before fitting it to the facade (projection 30–40 mm, +10 mm under the frame, end caps, expansion) (in Czech) | ZOFI fasády s.r.o. | undated | 14 October 2026 |
| 02 | Exterior pressed aluminium window sills – technical data (Al-Mg-Mn alloy 0.8 mm, depths 70–400 mm, max. length 6,000 mm, end caps) (in Slovak) | Widoor s.r.o. (retailer) | product page | 14 October 2026 |
| 03 | Tips & tricks – cladding walls and parapets (min. fall 3°, drip nose projection 40 mm / 25 mm, piece lengths) (in Slovak) | PREFA Slovakia | web article | 14 October 2026 |
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