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Fixings & Installation for Timber Cladding
An overview of the requirements to install timber cladding on your project.
How to install timber cladding
If you are unsure how to install your timber cladding, please get in touch for expert timber advice or choose a professional installer for the best results.
Before fitting, check that your chosen cladding profile is suitable for your project. Some cladding profiles are designed specifically for vertical or horizontal use, while others can be installed in either direction.
For horizontal exterior cladding timber, start at the bottom of the elevation with the tongue facing up and fix the first board securely. This ensures water runs off and does not sit in the groove. Use appropriate spacers as you work up the wall, making sure expansion gaps are included and boards stay level.
For vertical cladding, follow the same steps but you can work from either side of the elevation towards the centre.
Choosing the right timber battens
Timber cladding is usually installed on UC3 preservative treated softwood battens (Use Class 3 level of protection, ref. BS 8417) to ensure long term durability.
Treated softwood battens are commonly used, but due to natural movement in softwood timber, we recommend thermally modified Redwood battens for improved stability. This helps create a smoother, easier and faster installation. Thermowood battens are suitable for all timber cladding but are especially beneficial when working with fast grown species.
If standard treated battens are used, movement can occur. When battens shift in one direction and the cladding moves in another, the boards can begin to buckle on the façade and pull fixings out. Choosing stable battens from a trusted timber merchant helps prevent these issues and supports a long lasting exterior cladding timber installation.
Batten installation and specifications
In vertical applications, when using a cross batten system, chamfered horizontal profiles may be required as part of the batten setup. These help direct water away from the structure and, depending on the cladding profile, can sometimes be used on their own when cross battens are not essential. This will always depend on the specific cladding profile selected.
Common batten sizes include Ex 38 x 50 and 47 x 50mm, and it is important that battens are regularised to ensure consistent dimensions along the full length.
Thermowood D Battens do not require any preservative treatment.
Click to download information on timber battens.
Batten centres are typically set between 400 and 600mm for most installations. When fitting vertical cladding, a batten and counter batten system is usually required to allow airflow into the cavity and to enable moisture to escape at the base of the structure. Chamfered horizontal battens help guide excess moisture out of the cavity, supporting a long lasting and reliable exterior cladding timber installation.
| Minimum Batten Sizes mm (w x t) | |
| Vertical batten | |
| with allowance for side jointing* | 50×38 |
| no allowance for side jointing* | 50×25 |
| Horizontal batten | 50×38 |
| Counter batten | 50×25 |
*where a short batten length is fixed alongside a batten to enable boards to be butt jointed.
Fixings for timber cladding
Overview
Each board must be fixed independently. This allows any natural movement in the timber to be absorbed within the expansion gaps, helping the boards expand and contract without causing stress on the façade.
Fixing recommendations will vary depending on the species and board size, and whether face fixing or secret fixing is most suitable. For face fixing, use 2 fixings at the quarter points of each board at every batten centre. The fixing should sit flush with the face of the board. Overdriven fixings can allow moisture into the timber and should be repaired using an external grade filler.
Nail or screw dimensions must be appropriate for the board thickness and strong enough to secure the cladding. Annular ring shank fixings are recommended for treated softwood cladding supplied by a trusted timber merchant or timber supplier UK.
Diameter: Recommended minimum 2.3mm.
Material: Stainless Steel Grade 304
Length: For a regular 20mm cladding board, approx. 45mm fixing
Positioning: Quarter points, 20mm from ends of boards to reduce splitting, on dense species, pre-drill where necessary.Do not use a lost head fixing or panel pins as the opportunity for movement and for the boards to come lose is high.
Battens & Counter Batten Fixings
Where it is necessary to fix cladding battens to counter battens, use nails or screws as below. Horizontal batten spacing is wind load dependent. Pay attention to the closer spacing required.
Design wind load (kN/m²) Below 1.5 1.5 to 2.5 Nails Diameter (mm) 3.0 to 3.8 – Length (mm) 75 to 120 – Batten centres (mm) 200 – Screws Diameter (mm) 6 6 Length (mm) 110 to 180 110 to 180 Batten centres (mm) 400 300 Fixing Back to Primary Structure
The following tables give guidance for timber cladding assemblies carried out on a timber framed or mass timber backing wall. If the backing wall is masonry, connections between the cladding support battens and backing wall need to be designed by a structural engineer.
Fastener sizes for connecting vertical battens or counter battens to the backing wall (for horizontal boards or vertical boards with flat rear face).
Design wind load (kN/m²) Below 1.5 1.5 to 2.5 Nails Diameter (mm) 2.8 to 3.8 3.4 to 3.8 Length (mm) 75 to 120 90 to 120 Batten centres (mm) 150 150 Screws Diameter (mm) 5 5 Length (mm) 90 to 120 90 to 120 Batten centres (mm) 200 150 Fastener sizes for connecting horizontal battens to the backing wall (for vertical board-on-board timber cladding)
Design wind load (kN/m²) All wind loads below 2.5 Nails Diameter (mm) 3.8 Length (mm) 100 to 120 Batten centres (mm) 600 Screws Diameter (mm) 5 Length (mm) 90 to 120 Batten centres (mm) 600
Protecting timber cladding from ,oisture
To help your cladding perform at its best, every species and profile should be installed with the correct preparation. All cut ends must be end grain sealed to slow moisture absorption through the ends of the timber. This reduces the chance of the boards bulking during wetter months. Exposed end grain can absorb water up to 250 times faster than other timber surfaces, which may lead to internal rot or discolouration close to the cut edge.
As with any façade material, rainwater running down the face of the boards can carry dirt and debris. Good building design and detailing, including correct flashings and cills, will direct water away from the structure and help keep the cladding clean.
For vertical cladding or fins, all timber components should have chamfered tops and bottoms. This encourages water to shed rather than collect on the ends, reducing moisture ingress. Depending on the species, timber can readily absorb water which may lead to movement such as swelling or bulking. Chamfered ends should guide water back into the ventilation path behind the façade. If the angle pushes water forward, staining may appear on the cut edge. All cut ends should always be end sealed to protect the timber.
Installation guidelines and expansion gaps
Ensure the base of your cladding detail sits at least 200mm above any impermeable ground. This reduces splashing and helps prevent staining on the façade. Keep the area in front of the cladding free from vegetation, as close planting can affect the long term performance of the timber and increase the risk of surface staining.
When joining boards end to end, leave a 2 to 3mm expansion gap to allow for natural movement as the timber takes on and releases moisture. The same 3mm expansion gap should be used between boards during installation. Always use a spacer to maintain the 3mm gap and avoid pushing the tongue tightly into the groove.
Around the external perimeter of your timber cladding, leave an 8 to 10mm gap where the cladding meets other materials. This allows for movement and also creates a clean shadow line along the edge.
For project specific detailing, always check with your architect. These guidelines provide a general overview for installing exterior cladding timber from Benchmark, your trusted timber merchant and timber supplier UK.
Page Reference – TTF The Timber Cladding Handbook for specifiers, buyers and installers.