Choosing a window manufacturer is about more than finding the lowest price.
The manufacturer you choose can affect the quality of the finished windows, the choice of materials and glazing, how closely the products can be tailored to your property and, ultimately, how well everything performs once installed.
It can be particularly important when you’re replacing windows in an older London property. A standard off-the-shelf product may not always suit the proportions, style or requirements of the building.
So, what should you actually look for?
From manufacturing experience and materials to installation, guarantees and industry registration, here are eight things worth checking before placing an order.
What Should You Look for in a Window Manufacturer?
A good window manufacturer should be able to demonstrate product knowledge, quality manufacturing, appropriate materials, reliable installation and clear aftercare. You should also be able to get straightforward answers about specifications, lead times, guarantees and building regulations.
Here are eight areas to investigate.
1. Experience and Manufacturing Expertise
Start by looking at how long the company has been working with windows and what types of projects it handles.
Experience doesn’t automatically guarantee quality, but an established manufacturer should have a better understanding of different property types, window styles, materials and installation challenges.
This matters particularly when you’re dealing with unusual dimensions, period properties or bespoke designs.
Stroud Green Windows has been working in the industry for more than 20 years, with manufacturing and installation services for timber, uPVC and aluminium windows. The company also operates a local workshop, allowing greater control over the manufacturing process.
2. Can They Manufacture Bespoke Windows?
Not every property suits a standard-sized window.
If your home has unusual openings, traditional proportions or specific design requirements, ask whether the manufacturer can produce windows to your measurements rather than simply supplying standard products.
Bespoke manufacturing can allow you to specify details such as:
- Window dimensions
- Opening configuration
- Glazing pattern
- Frame material
- Colour and finish
- Hardware
- Traditional or contemporary detailing
For period properties, this can make a significant difference to the finished appearance.
Stroud Green Windows manufactures bespoke timber windows in different styles and sizes, with options for glazing patterns, hardware and finishes.
3. Check the Materials They Actually Use
A manufacturer should be transparent about the materials used in its windows.
Don’t settle for a description such as “premium quality” without asking what that means.
For timber windows, ask what type of timber is used and how it is treated. For aluminium, ask about the profile system and thermal performance. For uPVC, look at the profile, glazing options and reinforcement.
Different materials suit different properties, so the manufacturer should be able to explain the advantages and limitations of each rather than simply pushing one product.
4. Look at the Glazing and Hardware
The frame is only one part of a window.
The glazing, seals, hinges, handles and locking system all contribute to the finished product. Ask what glazing configurations are available and whether the manufacturer can accommodate your requirements for thermal performance, ventilation, security or noise reduction.
Hardware is worth considering too. Handles and locks are used every day, so poor-quality fittings can quickly become frustrating.
A good manufacturer should be able to explain the available options without relying entirely on technical jargon.
5. Check Who Actually Installs the Windows
This is an easy detail to overlook.
Some companies manufacture the windows themselves but use separate contractors for installation. Others manufacture and install as part of the same service.
There isn’t necessarily anything wrong with either approach, but you should know who is responsible for the installation before you agree to the work.
Installation quality matters because even a well-made window can perform poorly if it isn’t fitted, sealed and finished correctly.
Stroud Green Windows provides both manufacturing and installation services, including professional timber window installation in London.
6. Read Reviews and Look at Previous Projects
Reviews can tell you things that a product brochure can’t.
Look for comments about communication, workmanship, punctuality, installation quality and how the company dealt with problems. Don’t focus solely on the star rating.
Previous projects can also help you judge whether the manufacturer has experience with properties similar to yours.
For example, if you’re replacing sash windows in a Victorian terrace, examples of similar work are more useful than photographs of entirely unrelated modern developments.
7. Check Lead Times and Communication
Ask when your windows can realistically be manufactured and installed.
A manufacturer should be able to explain when the lead time starts and what could affect it. Design changes, glazing choices, paint finishes and hardware selections can all affect production.
Stroud Green Windows states that its typical lead time for supply-and-fit work is around four to five weeks, although this can extend during busier periods. Supply-only orders are typically around three weeks, with timings subject to change.
It’s sensible to confirm the current lead time when you request your quotation rather than relying on an older estimate.
Good communication is equally important. You should know who to contact if you have a question about measurements, design or installation.
8. Look Beyond the Initial Price
Price matters, but it shouldn’t be the only deciding factor.
Two quotations that appear similar may include very different products and levels of service.
Before comparing prices, check whether both quotations include:
- The same frame material
- Comparable glazing
- Similar hardware
- Removal of existing windows
- Installation
- Internal and external finishing
- Waste disposal
- Building regulations certification
- Guarantees or warranties
A cheaper quotation isn’t necessarily better value if important parts of the work have been left out.
Should You Buy Windows Direct From a Manufacturer?
Buying directly from a manufacturer can have advantages, particularly if the company also handles installation.
You may have a more direct line of communication with the people responsible for producing the windows. It can also make bespoke requirements easier to discuss because you’re not necessarily passing information through several different companies.
There can be practical benefits too. A manufacturer may have greater control over dimensions, materials, finishes and production schedules.
However, “direct from the manufacturer” isn’t automatically a guarantee of better quality. You still need to check the company’s experience, products, installation standards, guarantees and customer feedback.
Ask who manufactures the product, where it is manufactured and who will install it. If the answers are clear, you’ll have a much better understanding of what you’re actually buying.
How Can You Tell if Windows Are Good Quality?
Good-quality windows should feel solid, operate smoothly and have a finish appropriate to the material and design. However, quality isn’t something you can always judge from photographs.
If possible, visit a showroom or workshop and inspect the products yourself.
Look at:
Frame construction: Are the joints clean and consistent? Does the frame feel substantial?
Finish: Is the paint, stain, powder coating or surface finish even and well applied?
Hardware: Do handles, hinges and locking mechanisms operate smoothly?
Glazing: Ask what type of glazing is included and what performance characteristics it provides.
Seals: Check that seals and gaskets are neatly fitted without obvious gaps or poor finishing.
Operation: Open and close the window. It should move smoothly without excessive force or movement.
Installation: Ask to see examples of completed installations. The way a window is fitted is just as important as how it looks before installation.
If you’re considering timber, the quality of the material and finishing process deserves particular attention. Stroud Green Windows states that its standard windows use Scandinavian Redwood with hardwood cills, while other timber options including Oak, Accoya, Sapele and Meranti are available.
Which Window Material Is Best: Timber, Aluminium or uPVC?
There isn’t one material that is best for every property.
The right choice depends on the building, your budget, appearance, maintenance expectations and performance requirements.
| Material | Main advantages | Often suitable for |
| Timber | Traditional appearance, bespoke options, natural insulation | Period properties and homes where traditional detailing matters |
| Aluminium | Slim frames, strength, durability and contemporary appearance | Modern homes, extensions and larger glazed openings |
| uPVC | Low maintenance, practical performance and generally accessible pricing | Many modern and traditional residential properties |
Timber Windows
Timber remains a popular choice for period properties because it can reproduce traditional profiles and detailing convincingly.
It also offers considerable scope for bespoke design. Different timber species, paint colours, glazing patterns and hardware can be specified to suit the property.
Quality timber windows do require appropriate maintenance, but a well-made and properly finished timber window can provide long-term service.
Stroud Green Windows specialises in bespoke timber windows for traditional and contemporary London properties.
Aluminium Windows
Aluminium is particularly attractive if you want slim sightlines and a modern appearance.
Modern aluminium window systems can incorporate thermal breaks to reduce heat transfer through the frame. They are also strong and require relatively little maintenance.
This makes aluminium an option worth considering for contemporary homes, extensions and projects where larger areas of glass are desirable.
You can explore Stroud Green Windows’ aluminium windows in London for more information about available styles and finishes.
uPVC Windows
uPVC is widely used because it combines low maintenance with practical thermal and weather performance.
It can also be produced in several styles, including casement and sash designs.
For homeowners looking for a straightforward, low-maintenance solution, uPVC can be worth considering. Stroud Green Windows offers uPVC windows in London in a range of styles and finishes.
The key is not to ask which material is universally “best”. Ask which material makes the most sense for your particular property.
What Accreditations and Guarantees Should a Window Manufacturer Offer?
When choosing a manufacturer and installer, look for evidence that the business understands the relevant regulations and provides clear protection after installation.
FENSA Registration
For replacement windows and doors in existing homes in England and Wales, FENSA is one of the recognised competent person schemes.
FENSA explains that its Approved Installers are assessed for compliance with relevant Building Regulations. A FENSA certificate provides evidence that a qualifying replacement installation has been registered and complies with the applicable requirements.
Stroud Green Windows states that it is FENSA registered. Its registration number should be confirmed directly with the company before publication or use in promotional material.
It is important to understand that FENSA registration relates primarily to the installation and building regulations compliance, rather than being a product quality guarantee. FENSA itself states that its certificate is not a guarantee for the products.
Insurance-Backed Guarantees
Ask exactly what guarantee comes with your windows and installation.
A written guarantee should explain what is covered, how long the cover lasts and what exclusions apply.
An insurance-backed guarantee can provide additional protection if the installer stops trading. FENSA explains that qualifying installations registered after June 2014 can have insurance-backed guarantee protection, separate from the FENSA certificate itself.
Don’t simply accept “10-year guarantee” as enough information. Ask to see the terms.
Other Accreditations
Depending on the manufacturer and product, there may be other relevant certifications or memberships.
The important thing is to understand what each accreditation actually demonstrates.
A certification relating to installation competence is different from certification relating to a particular window system or product performance.
If a manufacturer advertises an accreditation, ask what it covers and whether it applies to the specific windows being supplied.
Get Everything in Writing
Before work begins, make sure the quotation and contract clearly state the products and services being provided.
This should include the window material, glazing specification, finishes, hardware, installation arrangements, expected timescales and guarantee terms.
FENSA recommends getting quotations, timeframes and certification arrangements in writing and comparing quotations on a like-for-like basis.
What Questions Should You Ask a Window Manufacturer?
Before choosing a manufacturer, it can help to have a short checklist ready.
Ask:
- Where are the windows manufactured?
- Are the windows made to measure?
- What materials and glazing options are available?
- Who will install the windows?
- Are you FENSA registered or part of another relevant competent person scheme?
- What guarantee is provided?
- Is the guarantee insurance-backed?
- Can I see examples of similar completed projects?
- What is the current manufacturing and installation lead time?
- What exactly is included in the quotation?
A manufacturer that answers these questions clearly gives you a much better basis for comparison.
Final Thoughts
Choosing a window manufacturer isn’t simply about finding someone who can supply the right number of windows.
You’re choosing the people responsible for the product, the specification and potentially the installation as well.
Look for a manufacturer that can explain its materials, show examples of previous work, provide clear specifications and offer appropriate guarantees. If you’re buying bespoke windows for a period property, make sure the company understands traditional proportions and the requirements of older buildings.
Most importantly, compare quotations on what you’re actually receiving rather than focusing on the headline figure.
If you’re considering new windows for a London property, contact Stroud Green Windows to discuss your requirements and explore suitable materials, styles and glazing options.
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Frequently Asked Questions
What should I look for in a window manufacturer?
Look for experience, transparent product specifications, bespoke manufacturing capability where required, quality materials, reliable installation and clear guarantee terms. It is also worth checking reviews and previous projects, particularly if you have a period property or unusual window requirements. A good manufacturer should be able to explain the differences between its products without relying on vague claims about quality.
Is it better to buy windows directly from a manufacturer?
Buying directly from a manufacturer can give you a more direct relationship with the people producing the windows and may make bespoke requirements easier to discuss. However, buying directly doesn’t automatically mean the products will be better. Check manufacturing standards, installation arrangements, reviews, guarantees and relevant certifications before making your decision.
How can I tell if a window is good quality?
Inspect the frame construction, finish, glazing, seals and hardware. A quality window should feel solid, operate smoothly and have clean, consistent finishing. If possible, visit a showroom or workshop and look at completed installations. Ask the manufacturer for details about the materials, glazing specification and product guarantees rather than relying solely on photographs or marketing descriptions.
Is timber, aluminium or uPVC best for windows?
There is no universally best window material. Timber is often well suited to period properties and traditional designs, aluminium offers strong, slim frames for contemporary projects, while uPVC is popular for its low maintenance and practical performance. The best choice depends on your property’s architecture, budget, maintenance expectations and performance requirements.
What accreditations should a window manufacturer have?
For replacement windows and doors in existing homes, check whether the installer is registered with a recognised competent person scheme such as FENSA. FENSA registration provides evidence relating to qualifying replacement installation and Building Regulations compliance. Other product certifications may also be relevant depending on the window system. Always check what a particular accreditation actually covers rather than treating every certification as a general quality guarantee.
What guarantee should I expect from a window manufacturer?
Ask for the guarantee in writing and check its duration, exclusions and exactly what it covers. You should also ask whether there is insurance-backed protection. A guarantee for the product is not the same thing as certification of installation compliance. FENSA explains that an insurance-backed guarantee can provide additional protection if a qualifying installer ceases trading.
Should a window manufacturer also provide installation?
Not necessarily, but you should understand who is responsible for fitting the windows before signing a contract. If the manufacturer also installs the windows, communication can sometimes be more straightforward because manufacturing and installation are handled by the same business. If installation is carried out by a separate company, check that installer carefully as well.
How many quotes should I get from window manufacturers?
Getting at least three comparable quotations is a sensible approach. Make sure each quotation specifies the same or equivalent frame material, glazing, hardware, installation and finishing work. The cheapest quotation isn’t necessarily the best value if it excludes important parts of the project. Comparing like-for-like specifications gives you a much clearer picture of the actual cost.