Everything you need to fit Alpha slatted composite cladding — sub-frame, fixing, trims, expansion gaps and aftercare. Read it here or download the printable PDF.
How to install Alpha slatted composite cladding — sub-frame, batten spacing, fixing, trims, expansion gaps and aftercare. Written for DIYers and trades, and it is the guide your 15-year warranty is measured against.
Alpha slatted composite cladding is a capped composite panel — recycled wood fibre and polyethylene, wrapped in our AlphaShield™ polymer cap — made to give the look of timber slats without the upkeep. Because it is a manufactured, pigmented product, order everything for one project at the same time: boards from one production run match, and you save on delivery too.
Before you fix anything, lay all the panels out and look at them together. Our brushed and woodgrain finishes carry natural tonal variation by design, and shuffling them now gives an even spread across the whole wall. As with any material in direct sunlight, a little weathering over time is normal.
The panels can be fitted to most wall types, and around windows, doors and corners, provided the right sub-frame and trims are used. If you are unsure which trims you need, talk to your builder or joiner — or to us — before you order.
Keep the panels cool, dry and out of direct sunlight, flat on a level surface that supports their full length so they cannot bow. Leave them at the site for at least 24 hours before fixing so they settle at the temperature they will live at. Wear gloves when handling or cutting, and carry each panel with two people — a 3.66 m panel weighs around 11 kg.
Alpha slatted composite cladding carries a 15-year residential warranty against warping, cracking, rot and fungal decay, subject to our terms and conditions. The cladding must be installed in line with this guide; departing from it may void the warranty. This guide is for reference and is not an exhaustive account of every installation situation — if in doubt, ask.
| Panel | 219 mm wide × 26 mm deep |
| Lengths | 3660 mm and 2250 mm |
| Coverage | 200 mm per panel |
| Area per panel | 0.72 m² (3.66 m) · 0.45 m² (2.25 m) |
| Weight | 10.83 kg (3.66 m) · 6.6 kg (2.25 m) |
| Profile | Four-slat face, hidden tongue & groove |
| Colours | Charcoal · Birch & Charcoal Silver Grey & Charcoal · Stone Grey & Charcoal |
Long sleeves and gloves whenever you handle or carry panels. When cutting, add a dust mask, ear defenders and safety glasses — composite dust is fine and you do not want it in your lungs or eyes.
Ordinary DIY and woodworking tools: tape measure, spirit level, pencil, utility knife, chalk line and a square. A string line helps on long runs.
Any standard wood-cutting tool will cut the panels. A mitre saw with a fine-tooth blade gives the cleanest edge by a distance; a jigsaw or circular saw with a fine blade handles cut-outs.
A cordless drill/driver with a clutch is all you need. Bring a 6 mm masonry bit for the battens, a small pilot bit for pre-drilling panels, and a countersink.
Non-negotiable. The battens must be flat and level or plumb, and every panel must be checked as it goes on. A 1.2 m level plus a short torpedo level covers everything.
| Item | Spec | For |
|---|---|---|
| Panel and trim screws | 35 mm, corrosion-resistant | Panels to battens through the grooved lip; trims at 300 mm centres |
| Batten fixings | 80 mm minimum + plugs | Battens to the wall — at least 50 mm into the substrate |
| Masonry bit | 6 mm | Pre-drilling batten and wall |
| Pilot bit | 3 mm | Pre-drilling every panel before a screw goes in |
| Packers / shims | Plastic | Levelling battens on an uneven wall |
Plan the batten layout before you buy anything, so every panel is properly supported. Look closely at:
Composite expands and contracts with temperature. Leave the panels at the site for 24 hours to acclimatise before fitting, and avoid installing in very hot or very cold weather — a panel fixed on a frosty morning will grow when the wall warms up.
Each 3.66 m panel covers 0.72 m²; each 2.25 m panel 0.45 m². Measure the wall height and width, subtract the openings, divide by the panel area and add 10 % for cuts — 15 % if there are several windows and doors.
Battens: total run ÷ 0.5 m, plus one, plus the perimeter, plus a twin at every butt joint. Trims: one per run edge and one per corner — they are handed, so fix your panel direction first.
So that each panel is supported independently at a joint, fit two battens side by side — around 20 mm apart, never closer than 5 mm. That gap doubles as the expansion allowance.
Pre-drill every panel and every batten before driving a screw. Composite splits if you go straight in.
Whatever batten you choose, keep a minimum 25 mm cavity between the wall and the panels. That is what lets the wall breathe.
Any of these will support the panels correctly: 50 × 30 mm composite (our Composite Joist), 50 × 50 mm recycled plastic, or 50 × 25 mm pressure-treated timber. Timber is fixed by the same method and gives the same support. Fix the batten flat to the wall; our 50 × 30 joist fixed this way gives a 30 mm cavity, comfortably over the 25 mm minimum.
Pre-drill both the batten and the wall behind it with a 6 mm bit. Fixings must go at least 50 mm into the substrate, so with a 30 mm batten you need screws of 80 mm or longer, with plugs to suit the wall.
For vertical panels the battens run horizontally, at 500 mm maximum centres, each one running the full width of the area to be clad. Always fix battens at 90° to the direction the panels will run.
Wherever two panels will meet end to end, fit twin battens so each panel end has its own support, with at least 5 mm between the two battens.
Run a batten round the whole perimeter as well. It closes the gap between panel and wall at the edges, and keeps debris, insects and small animals out of the cavity — while leaving the cavity itself open at top and bottom for air.
End and corner trims go on before any panels, fixed to the perimeter battens with 35 mm corrosion-resistant screws at 300 mm centres. Then fit the panels, leaving a 5 mm expansion gap wherever a panel meets a trim. For a consistent finish, complete one section before starting the next.
Start and end trims are handed: because of the tongue-and-groove profile, each one fits only one end of a wall, and which end depends on your panel direction. Measure and count them against that direction before you order. See Trims & profiles.
Stand the first panel against the start trim with its grooved edge facing the direction you are working, and set it truly plumb. Pre-drill through the grooved lip at every batten it crosses and drive a 35 mm screw into each — square, and stopped when the head sits flush. Do not overtighten.
Slide the next panel's tongue (the un-grooved lip) into that groove. It covers the screws of the panel before it. Push it home along its full length, give it a gentle pull to confirm it is tight to the battens, then fix through its own grooved lip. Repeat, checking plumb every third or fourth panel.
Where a panel meets an end trim, leave 5 mm. At an internal or external corner trim, leave 5–7 mm. The gaps let the panel sit into the trim without forcing the profile — cut panels to size on site where needed.
Where panels meet end to end, leave at least a 5 mm expansion gap between the ends, and land each end on its own batten of a twin pair spaced about 20 mm apart. One batten shared by two panel ends gives neither a solid fix.
Leave both the top and the bottom of the cavity open. That is what lets air move through and any water that gets behind the panels drain away. A perimeter batten closes the edge gap; it should never seal the cavity shut.
Two battens side by side at every butt joint, around 20 mm apart and never closer than 5 mm, so each panel end has its own fix and its own room to move.
Every panel, every batten, every fixing. It takes seconds and prevents splitting.
Minimum 25 mm cavity behind the panels, open at top and bottom.
Same sub-frame as for vertical: 50 × 30 mm composite, 50 × 50 mm recycled plastic or 50 × 25 mm treated timber, fixed flat to the wall with a minimum 25 mm cavity behind the panels.
Pre-drill batten and wall with a 6 mm bit. Fixings at least 50 mm into the substrate — 80 mm screws or longer with a 30 mm batten — with plugs suited to the wall.
For horizontal panels the battens run vertically, at 500 mm maximum centres, each one running the full height of the area to be clad, and always at 90° to the panels.
Twin battens wherever panel ends meet, at least 5 mm apart. A perimeter batten round the edge closes the edge gap without sealing the cavity.
Check every batten with a spirit level as you fix it. An error in the battens becomes an error in every panel above it.
L angle trims give the cladding a clean, finished edge at ends, corners, the top and the bottom. They can go on before the panels as a start or end trim, or after all the panels are in as a cover trim. See Trims & profiles.
A spirit level is essential when installing slatted cladding. Check every batten, the first panel, and then every third or fourth panel after it.
Where panels meet end to end, always leave an expansion gap of at least 5 mm. Land each end on its own batten of a twin pair spaced about 20 mm apart, so both ends get a solid, secure fix.
The last course will usually need ripping down. Cut it from the tongue edge — never the grooved edge — so the lip you fix through stays intact. Face-fix the top panel into the batten, pre-drilled and countersunk, and cover the fixings with the head trim.
Frame the opening with trim, mitred at 45° at the corners to picture-frame it. Keep 5 mm between every panel end and the inside of the frame.
Line the reveal: batten the return faces, panel them, and use corner trim where the reveal meets the wall face. Make sure the sill throws water clear of the cladding below.
Cut the hole 10 mm larger than the item and cover with a collar fixed to the item, not the panel. Never seal a panel rigidly to a pipe with silicone — it has to move.
| Ref | Part | Use |
|---|---|---|
| A | Slatted cladding panel 219 × 26 mm · ref 219H26 | The panel. Four-slat face, tongue on one edge, grooved fixing lip on the other. 200 mm coverage. |
| B | Start / end trim | Closes the first or last panel edge on a run. Handed — fits one end of a wall only, depending on panel direction. |
| C | External corner trim 2.25 m · colour-matched · AlphaShield™ capped | Wraps an outside corner and covers the panel ends on both faces. Also used at edges and heads. |
| L | L angle trim | General finishing angle for edges, corners, heads and bases. Goes on first as a start trim or last as a cover trim. |
35 mm corrosion-resistant screws at 300 mm centres. 2 mm between two lengths of trim end to end. 5 mm between a panel end and a start or end trim; 5–7 mm at a corner trim. Fit trims before panels wherever you can — except L angle trims, which can go on afterwards as a cover.
Composite moves with temperature; every gap gives it somewhere to go. In cold weather work to the larger figure; in heat the minimum is enough.
| Junction | Minimum |
|---|---|
| Panel end to start / end trim | 5 mm |
| Panel end to panel end | 5 mm |
| Panel to a corner trim | 5–7 mm |
| Panel to window or door frame | 5 mm |
| Panel to pipe, bracket or sill | 5 mm all round |
| Trim length to trim length | 2 mm |
| Between twin battens | 5 mm · 20 mm ideal |
Never in standing water, never bridging the damp-proof course. Minimum distances from the bottom edge of the lowest panel.
| From the cladding to | Minimum |
|---|---|
| Ground, path or patio | 150 mm |
| Flat roof or deck surface | 100 mm |
| Gutter, downpipe or soffit | 10 mm |
| Damp-proof course | Never bridge it |
| Cavity, top and bottom | Left open |
Wash the panels with lukewarm or cold water. For stubborn marks — bird droppings, for instance — add a little mild washing-up liquid and use a soft brush or sponge, then rinse. Wipe dust off with a damp cloth rather than a dry brush.
Once a year, inspect the panels and clean off any build-up of dirt, pollution or staining. While you are there, check that the bottom of the cladding is still clear of the ground, that nothing has been stacked against it, and that any planting has not closed off the cavity.
High-pressure cleaning systems must never be used. A pressure washer or jet wash damages the AlphaShield™ cap and the panel finish, forces water into the cavity behind the panels, and any damage it causes is not covered by the warranty. Lukewarm water, mild soap and a soft brush will shift anything a jet wash would.
If anything on your wall does not match what is in this guide — an awkward corner, an odd substrate, a wall you are not sure about — call us before you start. We would much rather talk it through first. We will also check a trim list for you before you order.
Download the printable PDF guide
We use cookies to give you the the best experience. By continuing you agree to our cookie policy.
Accept
.svg){kind=small}
