Custom Size UPVC Windows Perfect Fit for Every Opening in Your Home

Not every window opening is a standard size. Older homes, modern architectural designs, and unique spaces often require windows that simply do not come off the shelf. Custom size UPVC windows are manufactured to your exact measurements – width, height, shape, and configuration. This ensures a perfect fit, eliminates draughty gaps, and preserves the character of your property. This comprehensive guide explains everything you need to know about ordering and installing custom size UPVC windows.

Understanding Custom Size UPVC Windows

Custom size UPVC windows are made‑to‑order windows manufactured specifically for each individual opening. Unlike stock sizes (e.g., 1200x1200mm, 1500x1500mm), custom windows are extruded, cut, welded, and glazed to the precise dimensions you provide. This process allows any width from 300mm up to 2500mm, and any height from 300mm to 2500mm, in 1mm increments.

The frames and sashes are extruded from multi‑chambered virgin UPVC with UV stabilisers and impact modifiers. Steel reinforcement is inserted where needed – for larger sizes, the steel thickness can be increased (up to 2.5mm) to maintain structural rigidity. The glazing (double or triple) is cut to match the custom sash size, and all hardware (hinges, handles, locks) is fitted to the specific dimensions.

Custom sizes are available for all UPVC window types: casement (outward/inward), sliding (2‑track or 3‑track), tilt‑turn, awning (top‑hung), sliding sash (double‑hung), and fixed picture windows. Non‑standard shapes (arches, circles, triangles) are also possible but require additional engineering.

Key Advantages of Custom Size UPVC Windows

Perfect fit every time is the most obvious benefit. A custom size UPVC window is made to match the exact dimensions of your rough opening. This minimises the need for excessive foam filler or bulky trim, creating a cleaner finish and better thermal performance.

No draughts or air leaks. Because the window is precisely the right size, the gap between frame and structure is uniform and small. Proper sealing becomes easier, achieving air infiltration rates as low as 0.05 cfm/ft² – comparable to standard sizes.

Preservation of architectural character. Period homes often have windows with non‑standard proportions – tall narrow openings, short wide ones, or unique mullion arrangements. Custom size UPVC windows replicate those proportions exactly, maintaining the original aesthetic while upgrading to modern energy efficiency.

Seamless replacement in renovations. When replacing old windows, the new custom window can be made to fit the existing frame opening, avoiding costly structural modifications. This saves time, money, and disruption.

Optimal natural light and ventilation. You are not limited to stock sizes. You can maximise glass area in a given opening or create a window that matches the room‘s specific ventilation needs – for example, a very wide casement for a kitchen pass‑through.

Compliance with heritage and conservation requirements. Many conservation areas require windows to match original sizes, glazing bar patterns, and sightlines. Custom size UPVC windows can meet these strict requirements while delivering modern thermal performance (U‑values as low as 1.1‑1.6 W/m²K).

How to Measure for Custom Size UPVC Windows

Accurate measurement is critical. For replacement windows, measure the width and height of the existing frame opening at three points (top, middle, bottom for width; left, middle, right for height). Use the smallest measurement for width and height. For new construction, provide the rough opening dimensions after the framing is complete, and specify the required gap (typically 10‑15mm) for foam insulation.

Always order slightly smaller than the opening to allow for adjustment and insulation. Professional survey services are recommended for complex projects.

Applications for Custom Size UPVC Windows

Period home renovations – matching original timber window proportions.

New architectural homes – large format windows, narrow vertical lights, or wide horizontal ribbons.

Conservation areas and listed buildings – compliance with strict dimensional rules.

Renovation and retrofit – replacing old steel or timber windows without altering the facade.

Commercial buildings with non‑standard openings – shopfronts, industrial conversions.

Frequently Asked Questions About Custom Size UPVC Windows

Q: How much more expensive are custom size UPVC windows compared to stock sizes?
A: Typically 20‑40% more, depending on the size and complexity. Simple size variations (e.g., slightly taller) cost less; very large (over 2000mm) or narrow (under 400mm) sizes may cost more due to additional reinforcement. The premium is modest considering the perfect fit.

Q: What is the maximum size for a custom UPVC casement window?
A: For outward‑opening casement, maximum sash width is about 900mm, height 1800mm (glass weight limit ~80kg). Larger sizes require reinforced steel profiles or switch to a tilt‑turn or sliding design. Always consult the manufacturer.

Q: Can I get custom size UPVC windows in colours other than white?
A: Yes. Custom windows can be co‑extruded in any RAL colour or finished with woodgrain laminates (oak, walnut, mahogany). Dark colours require UV‑stabilised capstocks to prevent heat absorption issues.

Q: How long does it take to manufacture custom UPVC windows?
A: Typical lead time is 4‑8 weeks from order to delivery, compared to 2‑3 weeks for stock sizes. Complex shapes (arches, circles) may take 10‑12 weeks. Plan your renovation timeline accordingly.

Q: Do custom size UPVC windows need special installation?
A: Installation is similar to standard windows, but precision is more important because custom windows have less tolerance for out‑of‑square openings. Professional installation with careful sealing and flashing is strongly recommended.

Selection and Ordering Tips

When ordering custom size UPVC windows, work with a manufacturer that offers a survey service or provides detailed measurement guides. Provide drawings for non‑rectangular shapes. Specify the frame depth (typically 70mm for casement, 60mm for sliding), glazing (double or triple), hardware finish, and colour. Request a CAD drawing for approval before production.

Conclusion

Custom size UPVC windows are the ideal solution for non‑standard openings, period renovations, and any project where a perfect fit matters. They combine the energy efficiency, low maintenance, and security of UPVC with dimensions tailored to your home. With custom colours, glazing, and hardware options, you get a window that looks like it was always meant to be there.

Cooperate With Hunan Haolv Building Materials Co., Ltd.

As a leading manufacturer of high‑performance UPVC window systems, Hunan Haolv Building Materials Co., Ltd. brings over eighteen years of specialised expertise to the production of custom size UPVC windows. Our custom service includes any width/height in 1mm increments, any RAL color or woodgrain finish, double/triple glazing, and steel reinforcement for large sizes. We provide free technical consultation and full‑process project follow‑up. Every custom window undergoes rigorous ISO‑certified quality management. For detailed quotations, pricelist information, or to discuss your specific size requirements, please contact us today at kristin@haolvwindows.com.