How to choose a window and door supplier: the checklist for professionals

Choosing a window and door supplier isn’t a decision you settle with a price list PDF and a phone call. If you work as a window and door fitter, retailer or building contractor, an unreliable supplier hits your sites directly: missed deliveries, out-of-tolerance measurements, missing certifications at acceptance check time, dissatisfied end customers calling you.

This checklist comes from the direct experience of a manufacturer — not from someone reselling what others have made. Some items will look obvious, but those are exactly the ones that get skipped when you’re in a hurry.

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1. Systems and certifications: the non-negotiable starting point

CE marking on windows and doors isn’t optional. Under Legislative Decree 106/2017 and EU Regulation 305/2011 (CPR), every window or door placed on the European market must have:

• a Declaration of Performance (DoP) — the mandatory document certifying the declared performance (Uw, air permeability, watertightness, wind resistance);
• CE marking on the unit or on the packaging, referencing the EN 14351-1 standard.

A supplier who doesn’t hand you the DoP with the goods isn’t a supplier: it’s a legal problem you’re buying along with the product.

Beyond CE marking, ask which profile system is being used. The profile isn’t a neutral detail: two suppliers quoting you “5-chamber PVC window” could be using systems with very different Uf values, different application ranges, different accessory availability. If the supplier can’t tell you the make and code of the system they use, they don’t know what they’re producing. For a practical comparison between systems, read the article on Salamander GreenEvolution and BlueEvolution profiles.

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2. In-house production or intermediary?

This is the most important question, and it’s often not asked explicitly. The implications are concrete:

Manufacturer with its own plant:

• Direct control over tolerances, materials and lead times.
• Direct technical dialogue (you can ask for modifications, special configurations, samples).
• No hidden intermediation margin in the price.
• Clear liability in the event of a defect.

Retailer/wholesaler buying from third parties:

• The advantage can be prompt delivery from stock, if the stock genuinely exists.
• The downside is that the supplier has no control over what happens in production, and non-standard changes have unpredictable lead times.
• In the event of a dispute, the chain of responsibility is opaque.

There’s no model that’s wrong by default, but you need to know who you’re dealing with. Ask explicitly: “Do you have your own production plant, or do you buy from a subcontractor?” A vague answer is already a red flag.

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3. Production capacity and real lead times

A supplier who tells you “we deliver in 2 weeks” during negotiations and then, once the order is confirmed, pushes it to 6 weeks has either lied to you or doesn’t know how to measure their own capacity.

What to check:

• Average times by product type (standard windows vs. non-standard sizes vs. special shapes). Out-of-standard sizes require different setups.
• Peak vs. normal periods. At certain times of year (year-end, spring) production is at capacity. An honest supplier tells you in advance.
• Manageable volume per order. For sites with 50+ windows, check the supplier won’t get clogged up. For ongoing supply as a retailer, check they can sustain a monthly cadence.
• Order confirmation policy. The delivery date needs to be written into the order, not promised verbally.

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4. Single point of contact and account management

This point matters as much as the previous ones on the operational side. Having a single point of contact — who follows the order from intake through to post-delivery — isn’t a comfort: it’s a quality control. When problems arise (and they will), knowing who to call without being bounced between departments is the difference between solving it in 24 hours and losing a week.

Ask directly: “Who will be my point of contact? Is it the same person for the specification, production and complaints?” If the answer is “it depends on the relevant department”, brace yourself to act as coordinator between their departments every time a problem comes up.

Also check language and time zone. A supplier with production abroad but local, English-speaking management drastically reduces the risk of misunderstandings over technical specifications and specifications documents.

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5. Logistics and delivery

Logistics is often the critical sticking point in relationships with overseas or partly overseas manufacturers.

Points to clarify before ordering:

• Who organises transport? If they drop it off at the port and leave you to sort it out, factor in delays and hidden costs.
• Packaging: windows and doors travel upright, wrapped, on stillages. Inadequate packaging means broken glass on arrival — and then the argument over who pays begins.
• Delivery to floor level or kerbside from the lorry? For sites on the fourth floor with no lift, the difference matters a great deal.
• Goods insurance: who covers damage in transit?
• Time from confirmation to delivery: not “from production to dispatch”, but door-to-door until it reaches you.

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6. The private-label / third-party manufacturing option

If you operate as a window and door fitter under your own brand, or want to strengthen your brand with end customers, private-label / third-party manufacturing is a serious industrial tool. It isn’t “reselling someone else’s product with your sticker on it”: it’s production to order under your brand, with technical documentation and packaging in your name.

What to check when weighing up this option:

• Is the manufacturer willing to remove its own references from the packaging and documentation?
• Can the DoP be issued in your name (as the importer/distributor placing the product on the market)?
• Are the minimum order quantities compatible with your real volumes?
• Does the manufacturer agree not to contact your end customers, nor to sell the same products in direct competition in your area?

These points need to be clarified in writing — not verbally.

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7. Commercial terms and price list

The price list is the last point, not the first. Getting to a price comparison without having checked the previous points is like buying a car by looking only at the colour.

What to check in the contract or general terms:

• Fixed prices or variable based on raw material costs? In a market with PVC and steel price swings, a “locked” price list for X months has real value.
• Payment terms: a deposit on order plus balance on delivery is normal. 100% payment upfront before production is acceptable only with an established relationship.
• Defect management policy: what happens if a window arrives with a scratched profile, a faulty gasket, a wrong measurement? Who pays for the rework, and within what timeframe?
• Notice period for price changes: a serious supplier gives you a month’s notice, not a price list change on an order that’s already confirmed.

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Checklist summary

Area	What to check	Critical flag
Certifications	CE marking + DoP for every window/door	Yes — no sale without DoP
Profile system	Make, code, declared Uf	Yes — “5-chamber PVC” isn’t enough
Supplier structure	In-house production or intermediary	To be stated explicitly
Lead times	Written into the order, not just verbal	Yes — verbal statements don’t count
Point of contact	Single contact from specification to after-sales	Yes
Logistics	Who organises, packaging, insurance, door-to-door	Yes
Third-party manufacturing	Written agreement on brand, DoP, area exclusivity	If relevant
Terms	Locked price list, defect management, notice of changes	To be read, not signed on the fly

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Red flags: when to stop

Some signals should be taken seriously regardless of how attractive the price is:

• They don’t provide the DoP. Full stop. It doesn’t matter that “in all these years it’s never been needed”: it’s a legal requirement.
• They can’t tell you which profile system they use. It means they’re buying from someone who buys from someone who manufactures.
• Delivery times change after order confirmation without documented force majeure.
• No stable point of contact: every time you speak to a different person who doesn’t know what their colleague promised.
• Prices significantly below market with no credible explanation (e.g. in-house production with no intermediaries). Low cost doesn’t exist in manufacturing: what exists is a cost nobody has shown you yet.
• No samples available before ordering. A serious manufacturer provides a sample before starting production at volume.
• Punitive clauses on defect management: a defective window returned at their expense with rework within 30 days is normal. “Aesthetic defects can’t be disputed after 24 hours from delivery” is a clause that loads all the risk onto you.

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When it’s worth it / when it isn’t

It’s worth working with a direct manufacturer (not a wholesaler) if:

• You have recurring volumes, even modest ones, but consistent — that’s where a relationship gets built and a dedicated price list is earned.
• You need non-standard sizes, special shapes, RAL colours outside the standard range.
• You want production under your own brand (private label / third-party manufacturing) without sharing the end customer with the supplier.
• Your reputation is tied to the quality of the product you deliver — and you want to control the supply chain.

It’s not worth it (or less worth it) if:

• You need ready stock for delivery tomorrow. A made-to-measure manufacturer doesn’t hold warehouse stock: production times are what they are.
• You have very low, irregular volumes (one window every couple of months): a direct relationship with a manufacturer needs a minimum of continuity to be efficient for both sides.
• You already have a structured agreement with a local wholesaler that guarantees prompt delivery and local technical support.

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FAQ

Should I always ask for the DoP, even for small orders?

Yes. The DoP (Declaration of Performance) is mandatory for any CE-marked window or door placed on the Italian and European market, regardless of quantity. It isn’t a formality: in the event of an acceptance check, an incident or a dispute with the end customer, it’s the document that proves the declared performance. Make sure the supplier delivers it together with the goods, not “on request”.

Is manufacturing abroad a problem for CE certification?

No, provided the manufacturer has a factory production control (FPC) system compliant with EN 14351-1 and the DoP is issued properly. The geographic origin of the product doesn’t affect the validity of CE marking. What matters is that the system is certified and the documentation is in order.

How do I assess production capacity without visiting the plant?

A visit remains the best approach, but as an alternative: ask for concrete references (other fitters or contractors already working with them), ask for a realistically sized sample order and time it yourself, ask for written confirmation of delivery times — a supplier who backs away from written confirmation is telling you something.

Does third-party manufacturing require high minimum volumes?

It depends on the manufacturer. Some require high minimum thresholds, others handle single orders too. What matters is that the terms are clear from the start: minimum per order, monthly minimum, response times on variants. The details of private-label / third-party manufacturing vary by manufacturer — ask explicitly.

Can I get ongoing supply as a wholesaler without long-term commitments?

It depends on the contract terms. Many manufacturers don’t impose binding multi-year contracts, but offer dedicated price lists only to those who guarantee a degree of continuity. Buying wholesale from a manufacturer with recurring orders is the way to secure stable terms without excessively rigid commitments.

How do I protect myself if the supplier delivers the wrong measurements?

Protection is contractual and documentary: signed specifications at order stage, tolerances declared in writing (per EN 14351-1; the value varies by size and type — ±1.5 mm on the finished window/door is only an indicative order of magnitude), a written dispute procedure with defined response times. Without these elements, the argument over who’s right becomes purely a matter of contractual leverage.

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Choosing a window and door supplier is an industrial decision, not a purchase. The savings come from choosing the supplier who won’t cost you margin, time and reputation in the six months after you sign.

If you want to understand how we work and what we guarantee as a manufacturer, the starting point is the B2B production and supply page.