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Good timber cladding doesn’t fail because the timber is “wrong”. It fails at the edges: the corners, the base detail, the window reveals, the fixings, the cavity, the gap nobody thought about until the scaffold is up. This page sets out the practical cladding detail design approach we use for external timber cladding systems in the UK—clear, buildable, and aimed at long-term performance.
Cladding detail design – quick checklist
Cladding detail design is the translation of a timber façade idea into something that can be installed and will still be performing years later. It covers how the boards meet corners, how the cavity breathes, how water is managed, where fixings go, how movement is handled, and what happens around openings. Most defects trace back to a small set of avoidable issues: trapped moisture, insufficient ventilation, incorrect fixing selection, and rushed junction detailing.
A ventilated cavity is not optional detail—it’s the system. You want predictable drying, predictable drainage, and a cladding face that isn’t trying to behave like a tanking membrane. Get the cavity wrong and everything downstream becomes a patch.
| Detail element | What to achieve | Common failure mode |
|---|---|---|
| Air gap behind cladding | Continuous ventilation + drying path | Blocked sections around openings and corners |
| Insect mesh | Keep airflow while stopping pests | Mesh omitted or clogged with paint/debris |
| Base detail | Drainage + durability in splash zone | Boards too close to ground / standing water |
| Membranes | Water management + wind resistance | Tears, unsealed laps, compromised fixings |
A “sealed” façade often looks neat on day one and then quietly fails. A ventilated rainscreen detail rarely looks like a shortcut, but it stays dry and predictable.
Timber moves. It will move even if the supplier calls it stable. Fixing strategy needs to accept that and still keep the cladding flat, tight where it should be, and free where it needs to be. Detailing is where the difference shows—especially with long runs, vertical layouts, and open-jointed styles.
Window details are the reality-check of a cladding design. If you can’t draw it clearly, you can’t build it reliably. Good detailing does two things: it keeps water moving outwards, and it avoids trapping moisture where timber cannot dry.
| Junction | Design intent | Detailing note |
|---|---|---|
| External corners | Clean alignment + protected end grain | Plan end-grain sealing and consistent board returns |
| Window heads | Control water above openings | Include a proper flashing/drip and clear drainage path |
| Sills | Move water out and away | Avoid “backfall” and hidden traps behind trims |
| Base detail | Keep timber clear of splash + standing water | Set clearance, include mesh, ensure ventilation continuity |
If a project requires fire rated cladding (sometimes searched as fire resistant cladding or even fireproof cladding), the detailing becomes more coordinated—not more complicated, but less forgiving. Fire performance is rarely about one product alone. It’s the build-up, the cavity, the cavity barriers, the junctions and how the whole system is installed.
For product options, start here: fire-rated cladding and our main line fire-rated timber cladding boards. If you need the treatment/service side, see fire-retardant treatment.
Different timbers behave differently. Some are chosen for durability, some for stability, some for appearance. Detailing should respond to that choice rather than pretending every board behaves the same in British weather.
If you already know the profile you want, send it with your drawings—we’ll align the detailing approach to the actual board geometry and installation method.
If you want practical advice rather than generic diagrams, send: elevations/sections, timber choice (or shortlist), board profile/size, and any constraints (height, boundary distance, fire performance requirements). We’ll recommend a detail approach that is buildable and reduces the usual avoidable failures.
Most failures are moisture and detailing failures: insufficient ventilation, trapped water at junctions, poor base detail, or membranes and fixings that weren’t designed as a system. Timber quality matters, but details usually decide the outcome.
In most external cladding systems, a ventilated cavity is the proven approach because it supports drainage and drying. It also makes junction detailing more predictable and reduces moisture-related defects.
Species influences movement, durability, and finish behaviour. For example, ThermoWood is often chosen for stability, while Siberian Larch is chosen for durability and grain character. The detailing should match the material behaviour and exposure.
Yes. If the project requires fire rated cladding, we can advise on a practical detailing approach that aligns the product, build-up, cavity design and barriers. Product starting points: fire-rated cladding and fire-rated timber cladding boards.