Facade Cladding
Correct facade cladding protects your building against moisture, wind and fire. Learn about cladding types, air gaps, wind barriers and regulatory requirements.
Common cladding types
| Type | Service life | Fire class | Maintenance |
|---|---|---|---|
| Horizontal timber boards | 20–40 yr | D/E | Paint every 5–10 yr |
| Vertical timber boards | 25–50 yr | D/E | Paint every 8–12 yr |
| Fibre cement | 40–60 yr | A2 | Wash down; minimal painting |
| Brick slip / masonry | 50–80 yr | A1 | Near maintenance-free |
| Steel cassette / trapezoidal | 30–50 yr | A1 | Jet wash; repaint on damage |
| Larch / hardwood | 30–60 yr | D | Oil treatment as needed |
The fire-class letters are only an indicative guide to the bare material's reaction to fire. The permitted use is a property of the whole tested cladding system — the build-up, cavity, fixings and the wall behind it — and what is allowed depends on the building's height and use and on your local fire regulations. Treat this column as a starting point, not a compliance decision; confirm against the system documentation and a fire/building professional.
Wall build-up — cross section
From exterior cladding inward to internal lining:
Installation steps
Measure wall areas accurately. Deduct windows, doors and other openings. Add 10–12% for cuts and laps. Plan the starting point — usually a visible corner angle.
Calculate linear metres: Area ÷ visible board width (in metres).
Fix wind barrier membrane (sd-value ≤ 0.2 m) with counter-battens. Overlap at least 150 mm; tape joints.
Fix battens (e.g. 36×48 or 48×48 mm) at max 600 mm c/c over the wind barrier to create the air gap, using approved screws well anchored into the studs. The cavity must both drain and ventilate: for horizontal cladding run the battens vertically; for vertical cladding use vertical counter-battens plus horizontal battens, or notch/space horizontal battens so water can run down and air can rise. Continuous horizontal battens with no drainage path dam water behind the cladding.
Fix the first board with a ventilation starter strip. Bottom edge must be at least 250 mm above finished ground level. Check level.
A closing top strip seals the top against eaves or roof edge.
Use stainless or hot-dip galvanised screws/nails. Plain steel or zinc-plated corrodes quickly in coastal climates.
Fix at least 20 mm from board edge. Do not nail into the groove — boards must be free to move.
Corners: use mitre-cut corner trims (80×80 mm) or purpose-made corner boards. Keep maximum 5 mm gap against window reveals.
Seal the joints that need to be weather-tight — around window and door trims — with an elastic paint-grade sealant (never silicone on timber that will be painted). Do not seal the cavity closed: the ventilation openings at the bottom and top of the wall, and the drainage path, must stay open.
Exterior timber cladding needs a complete, compatible exterior wood-coating system — this may be a linseed-oil, alkyd or modern water-based system depending on the product and the timber; follow the coating manufacturer's specification. Coat all faces including the end grain BEFORE fitting — especially soffits!
Aim for 2 primer coats + 2 topcoats. Repeat every 5–10 years depending on exposure.
Local rules and practical requirements
Common mistakes
- ✗Air gap less than 25 mm — causes moisture and rot behind cladding
- ✗Cladding too close to ground (under 250 mm) — moisture wicking and decay
- ✗Untreated end grain — absorbs moisture fastest and rots first
- ✗Wrong screws — black steel corrodes and stains cladding
- ✗No movement joints on long runs (over 6 m without joint) — boards split
- ✗Wind barrier fixed outside the air gap — eliminates ventilation
When to call a professional
- ⚠Treating a bigger or taller building like a small one — beyond modest low-rise work, scaffolding, fall protection and a fire assessment to the local rules are needed, and the fire requirements for the cladding itself can change with height; use a contractor and confirm the thresholds locally
- ⚠Cladding near a property boundary — fire class assessment and possible building consent required
- ⚠Visible rot or moisture in the existing wall — the damage may extend deeper than the cladding alone
- ⚠Fibre cement and metal cassette systems — these require precise sub-structure design and the correct fixings
- ⚠Listed or heritage buildings — changing material or colour normally requires formal approval
Calculate facade cladding
Use the calculator to estimate linear metres of cladding, wind barrier area and screw quantities.
Open cladding calculator →Frequently asked questions
What air gap is required behind facade cladding?
A minimum 1" (25 mm) ventilated air gap is required behind all cladding types. This allows moisture to escape and prevents rot. SINTEF recommends 1–1.4" (25–35 mm) in coastal climates.
What overlap is correct for horizontal timber cladding?
Standard overlap for horizontal boards is around 1.5–2" (40–50 mm), but follow the board profile and manufacturer guidance. Keep the bottom edge well clear of the ground to avoid splashback and wicking — a clearance of roughly 8–12" (~200–300 mm, often quoted as ~250 mm) is a common guideline, but the exact figure depends on the detail, exposure and local rules.
What fire class does facade cladding need?
It depends on the building and is set by your local fire regulations, not a single universal threshold. Combustible cladding (e.g. untreated timber, typically Class D/E) is restricted by building height, distance to the boundary and building type, and may require a fire-rated system or non-combustible cladding instead. Figures sometimes quoted — for example needing a higher class such as Class B beyond ~2 storeys or close to a boundary — are only one example of such a rule. Always confirm the requirement with your local building code, and remember the rating applies to the whole tested cladding system, not the bare board.