What is a Composite Door? The Ultimate Buyer’s Guide

If you’ve walked down any street in Glasgow recently, you’ve seen a composite door. They have become the UK’s most popular choice for front doors, but at Williams Window Fabrication, we know that what’s inside the door matters just as much as the colour on the outside.

What is a Composite Door Made of?

Unlike a standard uPVC door, which is made from a single material, a composite door is made from a “composition” of materials. These are pressed together under high pressure to create a door that is thicker, stronger, and more thermally efficient than almost anything else on the market.

A typical Williams composite door consists of:

• A Glass Reinforced Plastic (GRP) Skin: This is essentially “fiberglass.” It’s incredibly tough, scratch-resistant, and can be moulded to look exactly like real wood grain without the risk of rotting or warping.

• A High-Performance Core: The “engine” of the door that provides strength and warmth.

• A Reinforced Frame: Usually uPVC with steel reinforcement for maximum security.

The Core Choice: High-Density Foam vs. Solid Timber

When you are browsing for a new door, you will likely come across two main types of cores. Both are excellent, but they offer different benefits depending on your home’s needs.

1. High-Density (PU) Foam Core

These doors feature a core made of high-density Polyurethane (PU) foam.

• The Benefit: Thermal Efficiency. Foam is a world-class insulator. A foam-filled composite door is significantly more energy-efficient than a traditional timber door, acting as a “thermal plug” for your hallway to keep the heat in and the West of Scotland wind out.

• The Feel: These doors are lighter than solid timber, making them easy to operate while still being incredibly secure.

• The Verdict: Perfect for homeowners prioritizing lower energy bills and a lightweight but sturdy door.

2. Solid Timber Core

As the name suggests, this core is made from multiple layers of solid timber—usually cross-laminated for immense structural integrity.

• The Benefit: Massive Strength. A solid timber core makes the door significantly heavier and denser. It offers a natural extra layer of acoustic insulation (perfect if you live on a busy road) and a higher level of impact resistance.

• The Feel: It feels like a traditional heavy oak door but with the low-maintenance benefits of a modern GRP skin. It gives that satisfying, “solid” thud when it closes.

• The Verdict: Ideal for those who want the ultimate “fortress” feel and traditional weight in their entrance.

Composite Doors vs uPVC or Timber Doors?

• Zero Maintenance: No sanding, painting, or varnishing. A quick wipe with soapy water once a month keeps it looking brand new for 25+ years.

• Better Security: Composite doors are typically 44mm or 48mm thick (compared to standard uPVC at 28mm). Combined with our multi-point locking systems, they are designed to exceed modern security standards.

• Energy Savings: With modern U-values, a composite door drastically reduces the amount of heat escaping through your front entrance.

Are All Composite Doors Built the Same?

Like anything, you get what you pay for. Whilst doors may appear the same, there are unseen differences which make a huge difference to the performance of the door:

1. Thermoplastic Coolskin outer layer: This construction prevents twisting and cracking, even in extreme weather conditions, delivering a door that performs beautifully year after year. Composite doors used to have a reputation for warping. the Coolskin technology is a crucial part of the battle against this. Make sure your new door has this technology.
2. Hardware: The quality of the hinges in particular play a huge part in how the door performs, and this is where a supplier can scrimp to increase margin or bring prices down.  A bad hinge is setting you up for ongoing misery. In terms of locks, look for an insurance-approved, high-security multi-point locking system as standard. This ensures your home and family keep safe, offering you peace of mind.
3. Glass: Many composite doors now come with triple glazing for maximal thermal insulation.

FAQs:

Are timber core composite doors fire safe?

Standard timber core composite doors are not fire-rated and should not be used where a fire door is required. However, they are solidly built and offer a high level of durability and resistance to daily wear. If fire safety certification is essential, look at our FD30 doors that meet legal requirements.

How do I maintain a timber core composite door?

Composite doors are low maintenance and easy to keep looking their best:

• Clean the surface with a soft cloth and warm, soapy water – avoid abrasive or solvent-based cleaners.
• Lubricate hinges, locks, and moving parts every six months with light engineering oil.
• To help prevent natural thermal movement, engage the locking points by lifting the handle every time you close the door.

Following these simple steps helps preserve the door’s appearance and performance over time.

Are solid timber composite doors a good investment?

Yes, a timber core composite door is a smart long-term investment. The solid core offers enhanced durability, security, and a high-end aesthetic that adds value to any property. With premium finishes, extensive style options, and exceptional weather resistance, these doors offer both kerb appeal and performance – ideal for homeowners wanting substance as well as style.

How are solid timber composite doors made?

Our solid timber core doors are engineered using a solid laminated timber core for strength and stability. This core is encapsulated in a Thermoplastic Coolskin® outer layer, known for its weather resistance and defined woodgrain finish. High-security multi-point locking systems and premium hardware complete the construction. Each door is precisely manufactured and finished to order, combining technology and traditional hand-finishing techniques.

Do solid timber composite doors fade?

Our timber core composite doors are designed to maintain their colour and appearance for years. The outer layer features Thermoplastic Coolskin® technology, which reflects heat and resists UV damage to help prevent fading. While all doors are subject to natural weathering over time, our premium composite offers enhanced resistance against colour loss, especially when maintained with occasional cleaning.

What colour can I have my Composite Door?

Our composite doors can be sprayed in any one of 1,600 RAL Colours across our Standard, Standard Plus, Premium and Exclusive Select ranges.

 

The Williams Way

We’ve been fabricating and installing doors for 30 years. We don’t just pick a door off a shelf; we select only the highest-specification slabs and hardware to ensure your door—whether it’s foam-filled or solid-core—is built specifically for the Scottish climate.

Ready to design your dream entrance? Explore our Composite Door Range or Book a Free Design Consultation today to see our samples in person!