- What it is: A machined rebate on each board edge creates a recessed horizontal shadow line between boards — clean, contemporary, no visible overlap joint.
- Standard size: 20x146mm — 20mm thick, 146mm face width. The most widely specified shadow gap cladding size in the UK.
- Also available: Double shadow gap 24x146mm (deeper rebate, bolder shadow), TG shadow gap 20x146mm (tongue and groove joint), double shadow gap 24x146mm.
- Durability: Siberian larch Class 3 — no treatment required, 20–30 year service life.
- Cost: £30–40/m² supply only. £60–90/m² supply and install.
- vs shiplap: Cleaner, more contemporary. Shadow gap suits new builds, extensions, garden rooms. Shiplap suits rural and traditional buildings.
- SSB/charred: Deep charred shadow gap is one of the most impactful contemporary cladding finishes available — black, textured, architectural.
Siberian larch shadow gap cladding is the most widely specified contemporary timber cladding profile in the UK — chosen for new build houses, house extensions, garden rooms, commercial buildings, and barn conversions where a clean horizontal shadow line and contemporary facade character are the design intent. This complete buyers guide covers everything you need to know about shadow gap cladding in the UK — what the profile is, what sizes are available, how it installs, what it costs, how it weathers, and how it compares to shiplap, tongue and groove, and rainscreen alternatives.
Siberian larch shadow gap cladding — the clean recessed horizontal shadow line between boards creates a contemporary, refined facade character. The 20x146mm standard profile is the single most widely specified timber cladding on contemporary UK buildings — houses, extensions, garden rooms, and commercial buildings.
What Is Shadow Gap Cladding UK — How the Profile Works
Shadow gap cladding is a timber cladding profile where a machined rebate on one or both edges of each board creates a recessed horizontal gap — the shadow gap — between adjacent boards when fixed to the wall. The shadow gap is typically 6–15mm deep and 8–12mm wide, depending on the profile specification. When viewed at any angle, the recessed gap creates a strong horizontal shadow line across the elevation — giving the facade a rhythm, depth, and contemporary character that flat-face shiplap and feather edge profiles cannot replicate.
The shadow gap profile differs from other cladding profiles in three key ways:
- No visible board overlap: Unlike shiplap or feather edge where one board overlaps the board below, shadow gap boards butt edge-to-edge with the rebated joint creating the visual gap. The board face is completely flush — there is no overlap to cast a shadow, only the recessed gap itself
- Clean board face: The face of each shadow gap board is flat and uninterrupted — no machined bead, no overlap, no texture. The clean board face allows the natural grain of the timber to be the primary visual element rather than the board profile
- Contemporary character: The horizontal shadow line reads as deliberately architectural — it is the profile that most clearly signals a contemporary, considered design intention. This is why shadow gap dominates on architect-designed houses, developer new builds, and high-specification garden rooms across the UK
Shadow Gap Cladding Sizes UK — Which Profile to Choose
Shadow gap cladding boards — the machined rebate on each board edge is visible in profile. The rebate depth and width determine the character of the finished shadow line — a deeper rebate produces a more pronounced shadow and bolder horizontal rhythm on the finished facade.
The dominant UK shadow gap specification — 20mm thick, 146mm face width, 8–10mm shadow gap depth. The correct size for most residential and commercial projects. Shop larch shadow gap 20x146mm.
Deeper double rebate — more pronounced shadow line, bolder horizontal rhythm. Best on larger elevations where the standard shadow gap reads as too subtle. Shop double shadow gap 24x146mm.
Tongue and groove shadow gap — boards interlock rather than butting. Tighter, more stable joint — suited to interior wall cladding and sheltered exterior applications where board movement needs to be constrained. Shop TG shadow gap.
ThermoWood shadow gap — Class 2 durability, zero maintenance, 25–40 years, most consistent grey weathering. The premium specification for shadow gap on commercial and maintenance-critical projects. Shop ThermoWood shadow gap.
ThermoWood shadow gap cladding — Class 2 durability, zero maintenance, 25–40 year service life. ThermoWood's consistent weathering to silver-grey makes it particularly suitable for shadow gap on large elevations where colour consistency across all boards is important — ThermoWood weathering is more uniform than Siberian larch on complex multi-elevation buildings.
Where Shadow Gap Cladding Is Used UK — Applications
The dominant profile for contemporary rear and side extensions on UK houses — the shadow gap creates a deliberate contrast with existing brick or render that signals architectural quality. See our extension cladding guide.
Increasingly specified on private sale new build developments where shadow gap larch or ThermoWood differentiates the product from volume housebuilder brick. See our new build cladding guide.
The most popular garden room cladding profile — shadow gap larch on a garden room or garden office creates an architectural, refined exterior that reads as designed rather than shed-like. See our garden room guide.
Shadow gap in ThermoWood or Siberian larch on commercial facades — offices, healthcare, education, retail. The clean board face and consistent shadow line suits contemporary commercial architecture. See our commercial cladding guide.
Contemporary barn conversions where planning allows a modern interpretation of the agricultural vernacular — shadow gap in black or grey is increasingly accepted by planning authorities on barn conversion projects.
Shadow gap is the most widely chosen profile when cladding over an existing brick house — the clean contemporary character of the shadow gap contrasts effectively with brick and creates a high-quality result. See our cladding over brick guide.
Charred Shadow Gap Cladding UK — Shou Sugi Ban
Deep charred shadow gap cladding — the combination of the clean shadow gap profile and Shou Sugi Ban charring creates one of the most architecturally impactful contemporary exterior finishes available. The black board face, recessed shadow line, and visible grain texture of charred timber produce a facade that reads as genuinely bold and deliberate.
Charred shadow gap cladding is one of the most searched and specified contemporary cladding combinations in the UK — combining the clean horizontal rhythm of the shadow gap profile with the bold, low-maintenance character of Shou Sugi Ban inspired charring. The result is a facade that achieves maximum architectural impact without the maintenance obligation of black-painted alternatives.
Our Shou Sugi Ban range includes charred, brushed, and stained finishes on Nordic spruce and Siberian larch — all available in shadow gap profiles. See our full charred cladding guide for the complete specification, and our black timber cladding guide for all black finish options including charred, stained, and ThermoWood black.
Shadow Gap vs Shiplap vs Rainscreen UK — Which to Choose
| Profile | Visual character | Shadow depth | Best application | Installation complexity |
|---|---|---|---|---|
| Shadow Gap 20x146mm | Clean, contemporary, flush face | Medium — recessed gap | Extensions, new build, garden rooms, commercial | Standard |
| Double Shadow Gap 24x146mm | Bold, architectural, deep shadow | Deep — double rebate | Large elevations, commercial, high-specification | Standard |
| Shiplap | Traditional, overlapping joint, deeper shadow | Medium — from overlap | Rural, barn conversions, traditional buildings | Standard |
| Rainscreen (open joint) | Most architectural — open joint, no fixings visible | Deep — open cavity joint | High-specification commercial, architectural residential | Higher — hidden fix system |
| Feather Edge | Traditional, agricultural, tapered overlap | Shallow — tapered overlap | Barn conversions, rural, agricultural buildings | Standard |
Grey shadow gap cladding — factory pre-greyed ThermoWood shadow gap achieves the weathered grey character from day one, without waiting the 2–5 years for natural weathering. Grey shadow gap cladding is increasingly popular on contemporary UK buildings where a consistent, even grey finish is required across all elevations from the day of installation.
Horizontal Shadow Gap Cladding UK — The Standard Orientation
Horizontal Siberian larch shadow gap cladding — the standard installation orientation. Horizontal boards with a recessed shadow gap produce a facade that emphasises the width of the building and creates a grounded, horizontal emphasis. Shadow gap also works vertically — see our vertical cladding guide for the vertical shadow gap specification.
Horizontal shadow gap cladding — boards running horizontally with the shadow line emphasising the horizontal plane — is the standard shadow gap orientation and the one that produces the classic contemporary UK cladding aesthetic. For vertical shadow gap cladding UK installation, the batten system must be inverted (horizontal support battens over vertical counter battens) — see our vertical timber cladding guide for the full specification difference and our installation guide for the step-by-step fixing sequence.
Shadow Gap Cladding Cost UK — 2026 Prices
| Profile & Species | Supply only (m²) | Supply & install (m²) | 25m² extension total |
|---|---|---|---|
| Siberian larch shadow gap 20x146mm | £30–40 | £60–90 | £1,500–2,250 |
| Siberian larch double shadow gap 24x146mm | £35–45 | £65–95 | £1,625–2,375 |
| ThermoWood shadow gap 19x140mm | £40–55 | £70–100 | £1,750–2,500 |
| ThermoWood double shadow gap 26x142mm | £42–58 | £72–105 | £1,800–2,625 |
| Charred shadow gap (SSB Nordic spruce) | £35–50 | £65–95 | £1,625–2,375 |
| Nordic spruce shadow gap | £12–18 | £42–55 | £1,050–1,375 |
See our full timber cladding cost per m² guide and our Siberian larch cladding cost guide for detailed pricing and whole-life cost analysis.
Shadow gap dominates UK cladding specifications for one simple reason — it is the profile that most effectively bridges the gap between the clean, flat facade of render and the richly textured character of timber. The shadow line gives the facade depth and rhythm without the complexity of rainscreen, the traditional character of shiplap, or the agricultural reference of feather edge. On a contemporary house extension, new build, or garden room, shadow gap larch or ThermoWood produces a result that reads as premium, contemporary, and designed — at a material cost that is accessible to most residential project budgets.
What is shadow gap cladding UK?
A timber cladding profile where a machined rebate on each board edge creates a recessed horizontal shadow line between adjacent boards. The most widely specified contemporary timber cladding profile in the UK — used on houses, extensions, garden rooms, and commercial buildings. Standard size: 20x146mm in Siberian larch.
What size is shadow gap cladding UK?
Standard UK shadow gap cladding is 20x146mm — 20mm thick, 146mm face width. Double shadow gap is 24x146mm. ThermoWood shadow gap is 19x140mm (single) and 26x142mm (double). Nordic spruce shadow gap is available in 14x120mm and 19x146mm.
How much does shadow gap cladding cost UK?
Siberian larch shadow gap 20x146mm — £30–40/m² supply only, £60–90/m² supply and install. ThermoWood shadow gap £40–55/m² supply only. Nordic spruce shadow gap from £12–18/m² supply only. A 25m² extension elevation costs approximately £750–1,000 for larch shadow gap boards supply only.
Is shadow gap better than shiplap cladding UK?
Different rather than better — shadow gap is cleaner and more contemporary, shiplap is more traditional. Shadow gap suits new builds, extensions, and garden rooms where contemporary character is the intent. Shiplap suits rural buildings, barn conversions, and traditional properties. Both perform equally well when correctly installed.
Can shadow gap cladding be installed vertically UK?
Yes — shadow gap works vertically and horizontally. Vertical shadow gap requires horizontal support battens (the batten system is inverted compared to horizontal installation). Vertical shadow gap creates a taller, more slender facade emphasis — particularly effective on narrow gable elevations and contemporary extensions. See our vertical cladding guide for the full batten specification.
Siberian Larch Shadow Gap Cladding — Supply UK Wide, 7–14 Days
We supply Siberian larch shadow gap 20x146mm, double shadow gap 24x146mm, ThermoWood shadow gap, Nordic spruce shadow gap, and charred Shou Sugi Ban shadow gap across the UK. FSC and PEFC certified. 7–14 day delivery. Free samples available.