Blog 01 · Technical guide
Sliding Window Series Explained: When to Choose 25mm, 27mm, or 29mm
Understanding METABUILD's ECO 1800, 2400, and 3000 series — and which one is right for your opening.
Introduction. If you have looked at the METABUILD sliding system catalogue, you have probably noticed the three main series — ECO 1800, ECO 2400, and ECO 3000. The numbers refer to the maximum leaf height each system supports: 1800mm, 2400mm, and 3000mm respectively. But there is more to choosing the right series than panel height. Here is how to think about it.
The 25mm series — ECO 1800
The ECO 1800 is the 25mm sash system, designed for standard residential openings with a maximum leaf size of 900mm wide by 1800mm tall. It is the right choice for bedrooms, living room windows, and apartment openings where the panel size is standard and the project is cost-sensitive. Available in Standard, Premium (wider frame), and Sleek (ultra-thin track, concealed bottom option) variants.
The 27mm series — ECO 2400
Step up to the ECO 2400 when your opening needs larger panels — up to 1200mm wide by 2400mm tall. The 27mm sash and reinforcement interlocking system handle the additional panel weight and wind load that larger openings demand. This is the most widely used series in South Indian residential and light commercial projects. Again available in Standard, Premium, and Sleek variants.
The 29mm series — ECO 3000
The ECO 3000 is built for tall openings — panels up to 1500mm wide by 3000mm tall. This is the villa series: floor-to-ceiling sliding panels for living rooms, pool-facing walls, and premium residential developments. The heavier sash and reinforced interlock maintain structural integrity at these dimensions. Choose the Sleek variant for a concealed track and maximum glass visibility.
Which series for your project?
Standard apartment or mid-range residential: ECO 1800 or ECO 2400. Premium apartment or larger openings: ECO 2400 or ECO 3000. Villa, floor-to-ceiling, design-forward: ECO 3000 Sleek. If you want the thinnest possible track on any system, choose the Sleek variant — it reduces frame depth from 38mm to 27.5mm and offers a concealed bottom track option.
Key takeaway. The series number tells you the maximum leaf height. The variant (Standard / Premium / Sleek) tells you the frame width, interlock type, and track depth. Match both to your opening size and aesthetic requirement. Download the METABUILD System Catalogue for full section data and typology drawings for all three series.
Blog 02 · Technical guide
Powder Coating on Aluminium: Why Pre-Treatment Matters More Than the Brand
The coating brand on the tin is only part of the story. What happens before the powder goes on determines how long it lasts.
Introduction. When fabricators and project specifiers ask about coating quality, the first question is usually about the brand — JOTUN, INTERPON, or similar. These are important. But the coating brand only determines the quality of the powder itself. What determines how long that powder stays on the aluminium — and how well it protects the profile — is the pre-treatment process that happens before any powder is applied.
What is pre-treatment?
Pre-treatment is a multi-stage chemical process applied to the aluminium surface before powder coating. Its purpose is to clean the surface completely, create conditions for maximum adhesion, and build in corrosion resistance from the metal up. Without proper pre-treatment, even the best powder coat brand will begin to peel, blister, or show corrosion within a few years — especially in humid or coastal environments.
The key stages
A proper pre-treatment process includes: degreasing (removes oils and surface contamination), etching (creates micro-roughness for adhesion), chromate conversion coating (the critical corrosion-resistance layer), and a deionised water rinse to remove all chemical residues. Each stage must be completed correctly and in sequence. Skipping or shortcutting any stage weakens the final finish.
Why the chromate conversion step matters most
The chromate conversion coating is the layer between the aluminium and the powder coat. It bonds chemically to the metal surface and provides the corrosion resistance that allows the coating warranty to stand. For exterior applications — windows, doors, facades — and especially for coastal projects where salt air accelerates corrosion, this step is non-negotiable.
What this means for specifiers
When evaluating a powder-coated aluminium profile, ask not just which brand of powder was used, but whether the facility runs a full pre-treatment process in-house. Third-party coating shops vary widely in their pre-treatment standards. At Alucraft — where all METABUILD profiles are coated — the full seven-stage process is applied to every profile, which is why we can back our coating with warranties of up to 25 years.
Key takeaway. A 25-year powder coat warranty is only meaningful if the pre-treatment behind it is done correctly. The brand of powder matters. The process that prepares the aluminium for that powder matters more. Learn more on our
Surface finish page.
