- Shadow gap cladding is a timber profile with a recessed groove machined into the face of each board — creating a precise shadow line at every joint for a contemporary, three-dimensional facade appearance.
- Available as single, double and triple shadow gap — each creating a different visual rhythm and frequency of joint lines across the facade.
- Available in four species — Siberian larch, ThermoWood, Nordic spruce, and charred timber — each with different performance, maintenance, and cost profiles.
- Can be installed horizontally or vertically — both orientations suit contemporary UK architecture.
- Material costs range from £26 to £120 per m² depending on species — from budget Nordic spruce to zero-maintenance charred timber.
Shadow gap cladding is one of the most specified exterior timber profiles in UK contemporary architecture. Its recessed groove detail creates a precise, consistent shadow line at every board joint — giving facades a three-dimensional quality and a refined, architectural appearance that flat-faced profiles cannot achieve. This guide explains exactly what shadow gap cladding is, how the profile works, the difference between single, double and triple shadow gap, which species to choose for your project, and what installation and maintenance to expect.
We supply shadow gap cladding in Siberian larch, ThermoWood, Nordic spruce, and charred timber — all from UK stock with nationwide delivery in 7–14 days. This guide will help you choose the right species, profile, and size for your project.
What Is Shadow Gap Cladding?
Shadow gap close-up — the recessed groove machined into the face of each board creates a consistent shadow line at every joint. The depth and width of the groove determines how pronounced the shadow effect is at different times of day.
Shadow gap cladding is a horizontal or vertical timber cladding profile in which a precisely machined recessed groove runs along the face of each board. When boards are installed edge to edge using a tongue and groove fixing system, the recessed grooves align to create a continuous shadow line at every joint. The groove captures and holds shadow at different times of day and in different lighting conditions, giving the facade a three-dimensional, architectural quality that flat-faced boards cannot achieve. The shadow line changes character through the day as the angle of sunlight shifts — sharper and more defined in low-angle morning and evening light, subtler in direct overhead light.
The shadow gap profile differs fundamentally from shiplap or feather edge cladding in its visual intention. Shiplap's overlapping joint creates a practical weather seal with a stepped visual result. Shadow gap's tongue and groove fixing is concealed behind the face of the board, meaning the only visual element at each joint is the precise recessed groove — a deliberate, designed detail rather than a structural necessity. This makes shadow gap the profile of choice for projects where architectural precision and visual refinement are the brief.
Shadow gap profiles are available in single, double, and triple variants — each with a different number of grooves per board and therefore a different visual rhythm across the facade. The choice between them is primarily a design decision driven by the scale of the building and the visual frequency of joint lines wanted.
Single, Double and Triple Shadow Gap — Which to Choose?
| Profile | Grooves per board | Visual effect | Best for | Available species |
|---|---|---|---|---|
| Single shadow gap | 1 | One shadow line per joint — clean, restrained horizontal rhythm | Residential extensions, garden rooms, traditional contemporary | Larch, ThermoWood, spruce |
| Double shadow gap | 2 | Two shadow lines per board — bolder pattern, wider board appearance | Larger facades, commercial buildings, contemporary new builds | Larch, ThermoWood, spruce |
| Triple shadow gap | 3 | Three shadow lines per board — finest, most frequent horizontal rhythm | Architect-designed projects, high specification residential and commercial | ThermoWood (Lunawood) |
The single shadow gap is the most versatile and widely used profile — its one groove per board creates a clean, considered joint line that suits a broad range of project scales and styles. The Siberian larch shadow gap 20x146mm and ThermoWood shadow gap 19x140mm are the two most popular single shadow gap profiles in our UK range.
The double shadow gap 24x146mm suits larger facade areas where a bolder, less frequent joint pattern is wanted — the wider board and two grooves create a more architectural, monumental result. For triple shadow gap, the Lunawood ThermoWood triple shadow gap is the most widely specified in the UK — see our dedicated Lunawood triple shadow gap guide for full details.
ThermoWood Shadow Gap — Low Maintenance, Long Life
ThermoWood shadow gap cladding — the warm honey-brown colour and consistent grain of thermally modified timber, with the recessed groove creating a precise shadow line that defines the facade rhythm.
ThermoWood shadow gap is the most specified shadow gap profile for contemporary UK projects where low maintenance is a priority. Thermally modified Nordic pine produces a dimensionally stable board that moves very little seasonally — meaning the shadow groove lines stay sharp and consistent over time, rather than opening or closing as the boards expand and contract. This dimensional stability is one of the key reasons ThermoWood is preferred over untreated species for precision shadow gap profiles.
ThermoWood shadow gap requires no preservative treatment — it can be left to weather naturally to silver-grey or maintained with a UV-stable exterior oil every 4–6 years. The BRE-accredited 30-year service life and Durability Class 2 classification make it one of the most robust exterior cladding specifications available in any softwood species. For a full overview of ThermoWood shadow gap and triple shadow gap profiles see our Lunawood ThermoWood cladding guide.
Shadow Gap Weathered — The Grey Finish
ThermoWood shadow gap weathered to silver-grey — one of the most popular low-maintenance exterior finishes for UK contemporary architecture. The shadow groove remains clearly defined throughout the weathering process.
One of the most important things to understand about shadow gap cladding — in any species — is that the shadow groove remains clearly visible and well-defined throughout the natural weathering process. Unlike shiplap or feather edge profiles where the stepped joint becomes less visually distinct as the timber weathers, shadow gap's recessed groove continues to catch and hold shadow regardless of the surface colour. This means the profile retains its architectural character even as the timber transitions from its original colour to natural silver-grey.
For ThermoWood and Siberian larch shadow gap, the natural weathered silver-grey finish is one of the most popular specifications precisely because it requires no ongoing maintenance while continuing to look considered and intentional throughout the service life of the building. The combination of the shadow gap profile and the weathered grey tone has become one of the defining visual signatures of contemporary UK residential architecture.
Shadow Gap Cladding by Species — Which Is Right for Your Project?
Nordic spruce shadow gap — the most affordable shadow gap option, suited to budget-conscious projects where regular maintenance is accepted.
Deep Charred Shadow Gap — The Statement Finish
Deep charred shadow gap cladding — the combination of the carbonised black surface and the recessed groove creates one of the most striking exterior timber finishes available. Zero maintenance required throughout the 25–40 year service life.
Charred timber shadow gap is the most visually striking shadow gap specification available — and one of the most practical from a maintenance perspective. The Shou Sugi Ban inspired deep charring process creates a carbonised surface that is inherently weather-resistant, while the shadow gap groove cuts through the char layer to reveal the natural timber beneath — creating a dramatic contrast between the deep black surface and the lighter groove interior.
The result is a facade with exceptional depth and visual complexity — the shadow groove catches light differently at different times of day, the char texture adds further surface interest, and the overall effect is a building that looks genuinely considered and architecturally ambitious. For garden offices, contemporary house extensions, and commercial buildings where bold visual impact is the brief, charred shadow gap is one of the most effective single-material facade treatments available. See our full charred timber range for available profiles and finishes.
Installation — Key Requirements for Shadow Gap Cladding
Shadow gap cladding installs over a ventilated batten framework in the same way as other closed-board profiles. However, because the shadow gap profile's visual quality depends on precise, consistent board alignment, a few installation details deserve particular attention:
- Consistent board spacing — shadow gap boards should be installed tight edge to edge with the tongue fully engaged in the groove. Any variation in spacing will show as inconsistency in the shadow line width across the facade.
- Ventilated cavity minimum 25mm — essential for long-term performance in all species. The tongue and groove fixing is more weathertight than shiplap but still requires adequate cavity ventilation behind the boards.
- Stainless steel fixings — A4 stainless steel screws or secret fix clips. The shadow gap profile typically uses secret fixing clips at the tongue rather than face fixing through the board, keeping the face entirely clean of visible fixings.
- Level batten framework — shadow gap's precise profile makes any irregularity in the batten framework more visible than with shiplap or feather edge. Take time to ensure battens are perfectly level before installing the first board run.
- Ground clearance 150mm minimum — standard requirement for all exterior timber cladding. Ground splash-back is the most common cause of early deterioration at the base of any cladding system.
For most UK residential and garden room projects — Siberian larch shadow gap 20x146mm is the strongest all-round specification. Natural durability, no treatment required, excellent weathering characteristics, and a price point that suits most budgets. For projects where dimensional stability and zero maintenance are critical — ThermoWood shadow gap is the better long-term specification. For maximum visual impact with zero ongoing commitment — charred timber shadow gap. For budget-sensitive builds where regular maintenance is accepted — Nordic spruce shadow gap delivers a contemporary result at the most accessible price point. For a full cost breakdown by species see our timber cladding cost per m² guide.
What is shadow gap cladding?
Shadow gap cladding is a timber cladding profile with a recessed groove machined into the face of each board. When boards are installed edge to edge, the grooves create a precise, consistent shadow line at each joint — giving the facade a three-dimensional, architectural appearance that changes with the light throughout the day. It is one of the most widely specified exterior timber cladding profiles for contemporary UK residential and commercial architecture.
What is the difference between shadow gap, double shadow gap and triple shadow gap?
Single shadow gap has one recessed groove per board face creating one shadow line per joint. Double shadow gap has two grooves creating a more frequent, bolder horizontal pattern. Triple shadow gap has three grooves creating the finest, most frequent horizontal rhythm — one of the most specified contemporary cladding profiles in the UK, particularly in ThermoWood.
Which is better — shadow gap in larch or ThermoWood?
ThermoWood shadow gap requires no treatment, has a 30-year BRE service life, and offers greater dimensional stability — groove lines stay more consistent over time. Siberian larch shadow gap is more affordable at £45–£65 per m², has natural character that suits both contemporary and traditional projects, and requires minimal maintenance. For low-maintenance projects, ThermoWood is stronger. For projects where cost and natural character are priorities, Siberian larch is excellent.
Can shadow gap cladding be installed vertically?
Yes — shadow gap can be installed horizontally or vertically. Horizontal is the most common, creating horizontal shadow lines across the facade. Vertical installation runs the grooves top to bottom, creating vertical shadow lines and a stronger upright visual emphasis. Both orientations perform well in the UK climate and the choice is primarily a design decision.
How much does shadow gap cladding cost in the UK?
Shadow gap cladding costs approximately £26–£38 per m² for Nordic spruce, £45–£65 per m² for Siberian larch, £55–£80 per m² for ThermoWood, and £75–£120 per m² for charred timber — materials only. Add £10–£15 per m² for battens, membrane and fixings, and £25–£45 per m² for installation labour.
Shadow Gap Cladding — All Species, All Profiles, UK Stock
We supply shadow gap cladding in Siberian larch, ThermoWood, Nordic spruce, and charred timber — single, double and triple shadow gap profiles from UK stock with nationwide delivery in 7–14 days. FSC and PEFC certified. Send us your species, profile, and m² for a precise quote.