Aluminium sash windows give an older home the look of a traditional sash window, panes that slide up and down rather than swing out, without the rotting timber, painting and snapped cords of the original. Coetz™ makes them as vertical sliding windows in eight standard sizes, delivered across South Africa. This guide explains how they differ from timber sash windows, the sizes and prices, what to know when replacing old windows and how to look after them.
In this guide
Timber sash or aluminium?
A traditional timber sash window hangs its sashes on cords and weights hidden in the frame. Over the years the timber swells and rots, the paint builds up, the cords snap and the sashes rattle or stick. Aluminium sash windows keep the same up-and-down opening but replace the cords and weights with a spring balance, so the sash stays where you leave it.
| Timber sash | Aluminium vertical sliding | |
|---|---|---|
| Sash support | Cords and weights | Spring balance |
| Painting | Every few years | Never; powder coated |
| Rot and swelling | Yes | No |
| Lock | Varies | Fitch catch included |
How they work
The sash runs up and down in channels in the side of the frame and stays where you leave it, so you can open it a little or a lot. A Fitch catch, included with the window, locks it closed. All visible hardware is black, and because nothing projects outwards, the window is safe beside paths and walkways. For the full background, see vertical sliding windows.
Aluminium sash windows sizes and prices
Because of the spring balance, aluminium sash windows are made only in the listed sizes, not to custom measurements. Standard Frame, White, excluding VAT, at the time of writing (October 2026):
| Size (mm) | Price |
|---|---|
| 600 × 900 | R3 494 |
| 600 × 1 200 | R4 214 |
| 900 × 900 | R4 203 |
| 900 × 1 200 | R4 620 |
| 900 × 1 500 | R5 093 |
| 1 200 × 1 200 | R5 327 |
| 1 200 × 1 500 | R6 587 |
The 44 mm commercial frame costs more (R3 941 at 600 × 900 mm) and suits larger buildings; see aluminium window frames.
Colours
White, Bronze and Charcoal cost the same; Black costs about 10% more. Natural Anodised is not available on aluminium sash windows. White or Charcoal usually suits an older facade best; see aluminium window colours.
Replacing old sash windows
- Measure the old opening with the timber frame removed, in three places each way; see how to measure aluminium windows.
- Choose the nearest standard size below the opening. Old openings rarely match modern sizes exactly, so your builder packs or adjusts the opening.
- Check local rules first. In a heritage area or a complex with design rules, check with the municipality or body corporate before changing the look of a facade.
- Plan the sills and reveals with your builder, so the new frame sits square and weathertight.
- Order and fit. Your builder or installer fits the windows.
For other old windows, see replace steel windows with aluminium and aluminium windows for renovations.
Where they work best
Aluminium sash windows suit older homes, farmhouses and townhouses where the original windows were sash, and any narrow opening next to a path or balcony where a sash swinging outwards would be in the way.
Looking after them
Vacuum the side channels where the sashes slide, wipe the frames with mild soap and water and rinse with clean water, more often at the coast. Do not oil the channels, because oil attracts dust. Never force a sash; if it sticks, clean the channel first.
Glass and ordering
The windows come with 6.38 mm clear laminated safety glass to SANS 10400-N, published by the South African Bureau of Standards. Coetz™ supplies aluminium sash windows ready to fit; your builder or installer fits them. We deliver across South Africa, or you can collect free from Laser Park.
Aluminium sash windows: frequently asked questions
Is a sash window the same as a vertical sliding window?
Yes. An aluminium sash window is a vertical sliding window: the sash slides up and down instead of swinging out.
Do they need cords and weights?
No. A spring balance holds the sash where you leave it, so there are no cords to snap.
Can I order a custom size?
No. Because of the spring balance, they are made only in the eight standard sizes, from 600 × 900 to 1 200 × 1 500 mm.
How much does an aluminium sash window cost?
From R3 494 excluding VAT for a 600 × 900 mm window in White with the Standard Frame.
Can I get them in Natural Anodised?
No. They come in White, Bronze, Charcoal and Black, but not Natural Anodised.
Coetz™, Unit 2, 84 Ridge Road, Laser Park, Johannesburg. Call 010 412 0062, WhatsApp 076 613 4418 or use our contact page.
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