A window’s energy rating, a conservatory roof’s insulation and a cladding system’s weather protection are all tested on the product.
But you only get that performance at home if it’s installed properly. That’s why who fits your product matters as much as what you buy.
We’ve already explained why we chose these manufacturers in the first place. This guide covers the other half: what being an approved installer actually means, what it protects, and how to check any company you’re considering.
What is an approved installer?
An approved installer is a company that a manufacturer has trained, assessed and authorised to fit its products.
Approval usually involves product-specific training, a commitment to install to the manufacturer’s specifications, and ongoing standards the installer must keep meeting.
In practice, it means the team on your driveway knows that exact system inside out: how it should be fixed, sealed and finished, and what the manufacturer requires for its warranty to apply.
Approved installer vs non-approved installer
*Swipe left on mobile
| Approved installer | Non-approved installer | |
|---|---|---|
| Training | Trained on the specific product system | Training on the product may be limited or unknown |
| Installation standard | Fits to the manufacturer's specifications | Methods can vary from job to job |
| Warranty | Installation supports the manufacturer's warranty | Incorrect fitting can put the warranty at risk |
| Product knowledge | Up to date on the latest ranges and options | May not know the full range or latest changes |
| Accountability | Answerable to the manufacturer as well as you | Answerable only to you |
| Genuine products | Supplies the manufacturer's genuine system | May substitute cheaper alternatives |
Does installation affect your warranty?
Often, yes. Manufacturer warranties are usually conditional on the product being installed in line with the manufacturer’s instructions.
If a problem is traced back to incorrect fitting, the manufacturer may decline the claim, leaving you to cover the repair.
Some manufacturers also offer their guarantees only through their approved network.
On top of product warranties, our work is covered by a 10-year insurance-backed guarantee through HomePro, so you’re protected even if a company stops trading.
What approval means in practice
Every product has installation details that make or break its performance. Here’s what our approvals cover for each system we fit.
Liniar windows and doors
A window’s thermal and security performance depends on how it sits in the opening.
As approved Liniar installers, we survey and measure precisely, then fix, pack and seal each frame to Liniar’s specifications so there are no gaps for heat, draughts or water to get through.
Poorly fitted frames can lose much of the benefit of an energy-efficient window. See our double glazing and doors.
SupaLite tiled conservatory roofs
Replacing a glass or polycarbonate roof with a tiled one changes the load on your conservatory.
As approved SupaLite installers, we assess the existing base and frames first, then install the roof system exactly as SupaLite specifies, and replacing a conservatory roof with a solid one often needs Building Regulations sign-off, which we manage.
Get it wrong and you risk structural movement, leaks or condensation. Read our SupaLite roof page and our red flag checklist.
James Hardie® HardiePlank® cladding
HardiePlank is fixed to battens that create a ventilated cavity behind the boards, which lets moisture drain and dry out.
As approved installers, we follow James Hardie’s installation guidance on batten spacing, fixings, trims, cut edges and cavity barriers.
Without it, cladding can trap moisture against the wall or fail around openings. Learn more on our HardiePlank cladding page or read Hardie Plank vs Render.
Why installation matters for each product
*Swipe left on mobile
| Product | What correct installation protects | Common risks if fitted wrongly |
|---|---|---|
| Liniar windows & doors | Energy efficiency, security, weather sealing | Draughts, leaks, condensation, sticking or insecure locks |
| SupaLite tiled roof | Structural stability, insulation, Building Regulations compliance | Structural movement, leaks, condensation, failed sign-off |
| HardiePlank cladding | Ventilated cavity, weather protection, long-term finish | Trapped moisture, loose boards, damage around openings |
How to check if an installer is genuinely approved
Anyone can put a manufacturer’s logo on a website. Before you sign, check:
- Ask for proof: A genuine approved installer will happily show their certificate or approval letter.
- Check with the manufacturer, as many list approved installers on their own website.
- Search independent registers such as TrustMark and Certass.
- Ask who will do the work and make sure it’s the approved company’s own trained team, not an unvetted subcontractor.
- Get the guarantee in writing, including who backs it if the company stops trading.
Greenoak's approvals and accreditations
We’re approved installers of Liniar uPVC windows and doors (and proud to be recognised in Liniar’s #ShareTheLiniarLove winner announcement), SupaLite tiled conservatory roofs and James Hardie® HardiePlank® cladding.
We’re also independently vetted and registered with:
- TrustMark, the Government-endorsed quality scheme for work in and around the home
- Certass, a UKAS-accredited body confirming our work meets Building Regulations
- HomePro, providing our 10-year insurance-backed guarantee
- Kestrel, as an Independent Registered Installer for fascias, soffits and guttering
Our own trained installation team carries out every job, and our customers rate us 4.9/5 on Trustpilot and 5.0 on Google. We cover the whole of Essex from our showroom in Westcliff-on-Sea, as well as parts of Kent and London. See our work in our case studies.
Approved installer FAQs
What is an approved installer?
An approved installer is a company that a manufacturer has trained and vetted to fit its products correctly.
It means the installer knows the system in detail and fits it to the manufacturer’s specifications, which protects both the product’s performance and its warranty.
What is the difference between an approved and a preferred installer?
The exact terms vary between manufacturers. Generally, approved means an installer has met the manufacturer’s training and quality standards, while preferred indicates a closer, longer-standing relationship or a higher level of recognition.
It is always worth asking an installer what their status involves.
Does using an approved installer affect my warranty?
It can. Manufacturer warranties usually depend on the product being installed according to the manufacturer’s instructions, and incorrect installation can put that cover at risk.
Approved installers are trained to fit products exactly as specified, and some manufacturer guarantees are only available through their approved network.
How can I check if an installer is genuinely approved?
Ask to see their approval certificate, check the manufacturer’s website for an installer finder or directory, and look them up on independent registers such as TrustMark. A genuine approved installer will be happy to show you proof.
What can go wrong if a product isn't installed correctly?
Poor installation can cause draughts, leaks, condensation, security weaknesses and early failure, even with a high-quality product.
For conservatory roofs it can lead to structural problems, and for cladding it can trap moisture behind the boards. It can also invalidate the manufacturer’s warranty, leaving you to pay for repairs.
Which products is Greenoak approved to install?
Greenoak Concept & Design are approved installers of Liniar uPVC windows and doors, SupaLite tiled conservatory roofs and James Hardie HardiePlank fibre cement cladding.
We are also TrustMark and Certass registered, and a Kestrel Independent Registered Installer for fascias, soffits and guttering.
What areas does Greenoak cover?
We are based in Westcliff-on-Sea and cover the whole of Essex, from Great Wakering to South Woodham Ferrers, as well as parts of Kent and London.
Ready to start your project?
Whether it’s new windows and doors, a warmer conservatory or a low-maintenance cladding makeover, you can be confident your home is in approved, experienced hands.
Book your free, no-obligation quotation or call 01702 238938, or visit our showroom at 96 Bridgwater Drive, Westcliff-on-Sea.
