Board type CMP-S and CMP-H
Solid composite decking, and when hollow will do
Composite boards come with either a solid core or a hollow one with channels running through it. Solid boards are heavier, stiffer and quieter underfoot. Hollow boards are lighter and cheaper, and perfectly good on a ground-level deck.
Fitted, hollow composite typically costs £95 to £160 per m². Solid boards sit in the capped range, £120 to £220, because nearly all of them are capped too.
- Solid, fitted
- £120 to £220 per m²
- Hollow, fitted
- £95 to £160 per m²
- Weight
- Solid is about 40% heavier
- Joists
- Hollow often needs closer spacing
Solid and hollow side by side
Solid boards are almost always capped; hollow boards often are not. That, more than the core, explains most of the price gap.
| Fitted, per m² | £120 to £220 | £95 to £160 |
|---|---|---|
| What it is | Wood fibre and recycled plastic, wrapped in a polymer shell | Wood fibre and plastic with hollow channels, often uncapped |
| Joist spacing | 300 to 400 mm centres | 300 to 350 mm centres |
| Upkeep | Wash in spring and autumn | Wash, plus a stain treatment if grease or leaves mark it |
| Board warranty | Often 25 years or more | Often 10 to 20 years |
| Fire | Combustible | Combustible |
| Best for | Most Leeds back gardens, shady or sunny | Ground-level decks on a tighter budget |
Solid and hollow prices by size
Level ground, frame and fitting included, no steps or balustrade.
| Deck | Area | Hollow | Solid, capped |
|---|---|---|---|
| Small, 3 × 3 m | 9 m² | £900 to £1,400 | £1,100 to £2,000 |
| Medium, 4 × 3.5 m | 14 m² | £1,300 to £2,200 | £1,700 to £3,100 |
| Large, 6 × 4 m | 24 m² | £2,300 to £3,800 | £2,900 to £5,300 |
| Very large, 8 × 4.5 m | 36 m² | £3,400 to £5,800 | £4,300 to £7,900 |
Typical UK fitted prices from published price lists we reviewed, October 2026, rounded to £100. National figures; a guide, not a quote.
The difference, plainly
A hollow board is extruded with tubes or slots running its full length. That saves material, so it is lighter and cheaper to make and to carry. A solid board is the same mix all the way through.
| Hollow | Solid | |
|---|---|---|
| Weight, typical 3.6 m board | About 9 to 11 kg | About 14 to 17 kg |
| Feel underfoot | Firm, can sound slightly hollow | Dense and quiet |
| Span between joists | Often 300 to 350 mm | Often 350 to 400 mm |
| Cap | Often uncapped | Nearly always capped |
| Cut ends | Need end caps or a fascia | Can be left open |
| Typical warranty | 10 to 20 years | 25 years or more |
Figures vary by maker. The data sheet for the exact board is the one to follow.
When solid is worth paying for
Choose solid boards when the deck will carry heavy loads or be seen from close up:
- Hot tubs. A filled hot tub weighs well over a tonne. It still needs its own base or extra joists, but solid boards cope better with the concentrated load.
- Raised decks. On a raised deck the cut ends and fascias are on show. Solid boards look cleaner and don't need end caps.
- Busy family decks. Solid capped boards resist dents from dropped toys and furniture better.
- Steps. Solid boards make sturdier treads and nosings.
When hollow is fine
On a small, low deck that gets ordinary use, a good hollow board on joists at the right spacing does the job for many years. It is the sensible choice for a terrace yard in Armley or Burley where everything has to be carried through the house, because the boards are so much lighter.
The catch is usually the surface, not the core. Many cheap hollow boards are uncapped, so they stain and fade faster. If you go hollow, look for a capped hollow board: you keep most of the saving and lose most of the drawbacks.
Water, frost and the hollows
People sometimes worry that water in the channels will freeze and split the board. In practice the channels are open at the ends and drain, and the ends are covered by an end cap or fascia that still lets water out. What matters is the slight fall built into the frame so water runs off, and a gap at the ends for movement.
Leeds sees plenty of frost on still winter nights, especially in the valleys. A properly fitted hollow board copes with it. A board laid flat in a dip, with its ends sealed tight, is where problems start.
Our view
If the budget allows, a solid capped board is the better buy over 20 years. If it doesn't, a capped hollow board is a far better choice than either an uncapped board or cheap timber. On a 14 m² deck the difference between hollow and capped is roughly £400 to £800.
Where our information comes from
- BSI, BS EN 15534-4: wood polymer composite decking profiles and tiles
- GOV.UK, Approved Document K: protection from falling, collision and impact
- Typical UK fitted prices from published price lists we reviewed, October 2026 (national figures)
Solid or hollow: questions
01Is solid composite decking better than hollow?
Solid boards are stronger, quieter and usually capped, so they last longer and look better. Hollow boards are lighter and cheaper and fine for low decks with normal use.
02How much more does solid composite cost?
Fitted, solid capped boards typically cost £120 to £220 per m² against £95 to £160 for hollow. On a 14 m² deck that is a few hundred pounds more.
03Can hollow composite decking hold a hot tub?
The hot tub needs its own base or extra joists whatever the board. Solid boards are the better choice around and under it.
04Do hollow decking boards need end caps?
Yes, or a fascia board across the ends. Open hollow ends collect leaves and insects and look unfinished.
05What joist spacing does hollow composite need?
Often 300 to 350 mm centres, a little closer than solid boards. Always follow the maker's figure, and reduce the spacing further where boards are laid at an angle.
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