Compare Solidor vs GRP composite doors. See why a solid timber core delivers better strength, security, and long-term performance in UK homes.
What You’ll Learn:
- How a timber core outperforms foam-filled GRP construction.
- Why Solidor resists attack where GRP composite doors fail.
- How Solidor delivers better insulation without flex or draughts.
- Why GRP composite doors need replacing sooner than Solidor.
(Estimated Reading Time: 8-9 Minutes)
Introduction: Composite doesn’t always mean equal
The word “composite” is used everywhere — but it rarely explains what a door is actually made of. Most GRP composite doors rely on thin skins wrapped around a foam-filled centre, designed to reduce cost rather than improve performance.
Solidor takes a different approach. Built around a solid timber core, it delivers strength, stability, and longevity that foam-based doors simply can’t match. After installing over 100,000 Solidors since 2008, we’ve seen first-hand how GRP doors age — and how Solidor continues to perform decades later.
This comparison explains the real differences between Solidor and GRP composite doors, without marketing spin or half-truths.
1. Core Construction: Foam vs Timber — the entire difference
If you read nothing else, read this section.
GRP Composite Doors (Budget Market)
- Thin GRP skin
- Polyurethane (PU) foam interior
- Lightweight
- Prone to bowing
- Cheaper to produce
- Lifespan: 8–12 years
Solidor
- 48mm engineered hardwood laminates
- Solid mass from edge to edge
- Heavy, rigid, stable
- Zero bowing under heat
- True timber strength without timber maintenance
- Lifespan: 20–25+ years
The core defines everything:
Security, soundproofing, longevity, thermal performance — even how the door feels to open and close.
A foam-core door feels hollow because it is hollow.
A Solidor feels like shutting a vault — because it’s solid.
Winner: Solidor. And it’s not even close.
2. Strength & Security: The “knife test” every homeowner should know
This is the bit no GRP manufacturer wants in writing, but every installer knows.
GRP Foam-Core Door Weaknesses
You can cut into the GRP skin with a sharp knife.
Behind it?
Air pockets and foam.
It looks strong. It isn’t.
We’ve replaced countless GRP doors after break-ins — not through the lock, but straight through the panel.
Solidor Security Advantages
- Solid timber core can’t be cut or snapped.
- Reinforced through the entire structure.
- Ultion 3-Star Plus lock as standard.
- Zero successful cylinder break-ins recorded in 17 years of our installs.
Whether you live in a city centre or a rural village, there’s no comparison:
A foam-core door can be breached.
A Solidor cannot.
Winner: Solidor by a country mile.
3. Thermal Performance: The myth of “foam is warmer”
Foam-core manufacturers love this line:
“Foam is more insulating than wood.”
Technically true. Practically meaningless.
Thermal efficiency is measured across the entire door system — panel, frame, seals, glazing.
Here’s the reality:
| Door Type | U-Value (Typical) | Real Efficiency |
|---|---|---|
| GRP (Foam Core) | 1.6–1.8 W/m²K | Adequate |
| Solidor (Timber Core) | 1.4 W/m²K | Excellent |
Why is Solidor warmer despite a timber core?
- Thicker door leaf
- Tighter compression seal
- Better frame construction
- No flex or bowing (which creates draught gaps)
In real UK homes, Solidor outperforms GRP every single winter.
Winner: Solidor.
4. Longevity: The most important factor homeowners forget to ask
A foam-core GRP door lasts around 8–12 years before:
- Warping
- Delamination
- Fading
- Handle misalignment
- Hinges pulling away from the frame
That’s why so many people who bought GRP doors in the early 2010s are replacing them now.
Solidor?
We have installs from 2008 still closing perfectly today.
Here’s our real-world lifespan data (not brochure copy):
| Door Type | Expected Lifespan |
|---|---|
| GRP Foam-Core | 8–12 years |
| Mid-Market Timber/Foam Hybrid | 12–15 years |
| Solidor | 20–25+ years |
You replace a GRP door once.
Then again.
Then again.
You buy a Solidor once — and forget about it.
Winner: Solidor, again.
5. Appearance & Finish: Glossy does not mean premium
GRP doors rely on a painted or gel-coated skin.
It looks shiny when new.
Then UV hits it.
Then the English weather hits it.
Then it chalks, fades, and cracks.
Solidor uses a thermo-plastic, UV-stable skin that:
- Doesn’t fade
- Doesn’t peel
- Doesn’t crack
- Cleans like new with warm water
If you’ve ever seen a chalky GRP door, you know exactly what we’re talking about.
Winner: Solidor — engineered finish, not cosmetic paint.
6. Weight & Feel: Daily use reveals the truth
GRP doors weigh between 15–25kg.
Solidors weigh 40–60kg.
That weight translates to:
- A more premium feel
- Less rattling in high winds
- No “hollow thud” when closing
- Better soundproofing
- Stronger resistance against impact
It’s the difference between shutting a cheap interior door and shutting something substantial and engineered.
Winner: Solidor.
7. Price: Foam is cheaper — and it shows
Here’s the part GRP manufacturers use to hook people:
| Door Type | Typical Installed Price |
|---|---|
| GRP Foam-Core | £900–£1,200 |
| Solidor (Fully Fitted) | £1,490–£1,750 |
And here’s the part they don’t tell you:
- GRP door lifespan is half.
- GRP colours fade faster.
- GRP hardware needs replacing sooner.
- GRP often voids warranty if it warps.
So yes, GRP doors are “cheaper.”
So is buying a new washing machine every year.
Winner: Solidor on long-term cost by a huge margin.
8. Real Customer Feedback: The before-and-after stories
“Replaced a GRP door after 9 years. It warped so badly it wouldn’t lock. The Solidor feels like proper engineering.”
– N. Rogers, Derby
“We bought a GRP door thinking all composites were the same. Big mistake. Our Solidor upgrade is night and day.”
– The Holmes Family, Cambridge
“I fit both as a tradesman. GRP is fine for rentals and budget jobs. But for your own home? Solidor every time.”
– M. Turner, Trade Installer (20+ years)
9. The Verdict: GRP is good — Solidor is exceptional
GRP composite doors exist for one reason:
To hit a price point.
Solidor exists for a different reason:
To be the best-performing composite door in the UK.
When you compare them side by side — core, strength, finish, longevity, thermal performance, security — the difference isn’t subtle. It’s glaring.
If you want a door for now, pick GRP.
If you want a door for the next 20–25 years, pick Solidor.
If you want it fitted correctly and guaranteed properly, pick us.
🛒 Browse online: www.timbercompositedoors.com
📞 Or Call us: 01642 309576 for expert advice
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FAQ’s
What is the main difference between Solidor and GRP composite doors?
The core. GRP composite doors typically use a foam-filled centre, while Solidor uses a solid timber core that delivers superior strength, security, and lifespan.
Are GRP composite doors less secure?
Yes. Foam-filled GRP doors are more vulnerable to panel attack and flexing, whereas Solidor’s timber core provides structural resistance across the entire door.
Is a timber core less energy efficient than foam?
No. Despite common claims, Solidor’s thicker leaf, tighter seals, and rigid construction outperform GRP composite doors in real-world thermal performance.
How long do GRP composite doors last compared to Solidor?
GRP composite doors typically last 8–12 years. Solidor doors routinely deliver 20–25+ years of reliable service.
