Everything You Need to Know Before Buying a Composite Door
Written by Cornwall Composite DoorsReviewed by Cornwall Composite Doors installersLast updated July 20268 minute read
Short answer
Before buying, check the door's core material and thickness, the guarantee length and what it covers, the hardware brand, glazing options, and whether the installer measures on site rather than quoting from photos. These factors affect performance and value far more than the headline price.
Composite doors vary a surprising amount between suppliers, even when they look similar in a brochure. Before you order one, it helps to know what actually separates a good door from a mediocre one, and what questions to ask your installer.
Check what's inside the door
The core material makes a big difference to how the door performs. Solid timber-reinforced cores or high-density foam cores generally give better thermal performance and rigidity than cheaper, lower-density fillers. Ask your installer what core their doors use — a reputable supplier will know the answer straight away.
Slab thickness and weight
Most quality composite doors have a slab thickness around 44-48mm, which gives a solid, weighty feel when you open and close it. A door that feels light or hollow when you knock on it is a sign of a lower-quality build, whatever the surface finish looks like.
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Hardware and locking
Multi-point locking should be standard, but the quality of the cylinder, handles and hinges varies. Anti-snap cylinders are worth insisting on. Cheap hardware can look fine on day one but wear or seize within a couple of years, especially in coastal air.
- Ask which lock brand is fitted
- Check hinges are adjustable, not fixed
- Confirm handle finish is suitable for coastal exposure
Glass and privacy
Glazed panels range from clear to fully obscured, and decorative designs can add real kerb appeal. Think about how much natural light you want in the hallway versus how much privacy you need from the street, particularly if your front door faces a pavement or neighbouring path.
Colour and finish
Ask to see a physical sample in your chosen colour rather than judging from a screen, as woodgrain texture and colour depth can look quite different in person. Also check whether the colour is through the skin or a surface coating, as this affects long-term appearance.
The guarantee, in detail
A long guarantee is only useful if it's written down clearly. Ask exactly what's covered — the slab, the hardware, the installation, or all three — and what would void it. We provide a 10-year written guarantee covering our composite door installations.
How the installer measures and fits
A proper quote comes from someone measuring your actual opening, checking the condition of the existing frame and structure, and explaining how they'll fit the new door. Be wary of quotes given without a site visit, since fit and finish depend heavily on the opening itself.
Frequently asked questions
What's the most important thing to check before buying?
The core construction and the guarantee terms matter more than most buyers realise. A door with a solid core and a clear, comprehensive written guarantee will outperform a cheaper door with vague or limited cover, even if the initial price looks similar.
Should I get more than one quote?
Yes, it's sensible to compare at least two or three quotes, but make sure you're comparing like for like — same core construction, hardware level and glazing — rather than just the bottom-line price.
Do I need building regulations approval for a new door?
Most external door replacements need to comply with building regulations for thermal performance and safety glazing, but a competent installer will handle this as part of the installation and provide the relevant certification.
Can I choose different colours inside and outside?
Yes, most ranges allow a different colour on the interior and exterior faces, which is popular where the outside needs to suit the street scene but the inside needs to match a hallway colour scheme.
How long does installation take?
A single composite door replacement is usually completed in half a day to a full day, depending on the condition of the existing frame and whether any brickwork adjustment is needed.
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More buying guides advice
- Ultimate Guide to Composite DoorsEverything in one place: what composite doors are made from, why they perform well in Cornwall's weather, and how to choose the right one.
- Are Composite Doors Worth the Money?Composite doors cost more than uPVC upfront. Here's an honest look at whether that extra cost is justified over the life of the door.
- What Makes a Good Composite Door?Not all composite doors are equal. Here's what actually separates a well-made, long-lasting door from a mediocre one.
