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Timber Decking Range | Treated Decking Boards, Joists & Accessories

Build a durable and attractive outdoor space with our timber decking range, featuring high-quality, pressure-treated boards and all the essential components for a complete decking system. Whether you're constructing a garden patio, raised deck, or commercial platform, our treated timber is built to last.

✅ Treated softwood decking boards – grooved and smooth profiles
✅ Decking joists & subframes – UC4 treated for ground contact
✅ Handrails, spindles & newel posts – perfect for balustrade systems
✅ Decking screws & fixings – rust-resistant and long-lasting
✅ Available in a variety of lengths and sizes

Ideal for landscapers, joiners, and DIYers, our decking timber offers strength, style, and ease of installation. Nationwide delivery available on all decking supplies.

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100mm x 47mm (4"x2") joist, square sawn

£10.70 - £14.28
£10.70 - £14.28
£10.70
£8.64 - £11.52
£8.64 - £11.52
£8.64
In stock

100mm x 47mm (4"x2") Joist, Square Sawn Enhance your construction projects with our durable 100mm x 47mm joists, available in various lengths ...

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£10.70 - £14.28
£10.70 - £14.28
£10.70
£8.64 - £11.52
£8.64 - £11.52
£8.64
Save up to 19% Save %

Redwood Treated Decking Board 145x28mm | 3.6m, 4.8m, 5.4m lengths

£10.73 - £15.60
£10.73 - £15.60
£10.73 - £15.60
£10.73
In stock

Our Redwood Treated Decking Boards (145mm x 28mm) offer a high-quality, durable solution for creating stylish and long-lasting outdoor spaces. Ide...

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£10.73 - £15.60
£10.73 - £15.60
£10.73 - £15.60
£10.73
Save up to 23% Save %

150mm x 47mm (6"x2") Joist, square sawn

£16.07
£16.07 - £16.48
£16.07
£12.36 - £16.48
£12.36 - £16.48
£12.36
In stock

150mm x 47mm (6"x2") Joist, square sawn Enhance your construction projects with our 150mm x 47mm (6"x2") Joist, pressure treated in an att...

View full details
£16.07
£16.07 - £16.48
£16.07
£12.36 - £16.48
£12.36 - £16.48
£12.36
Save up to 23% Save %
Save up to 44% Save %

125 x 47mm (5x2) Treated Timber Joist | C16 / C24 Regularised

£17.90
£17.90 - £17.90
£17.90
£10.08 - £14.94
£10.08 - £14.94
£10.08
In stock

Our 125 x 47mm (5x2) treated timber joists are strong, reliable, and versatile — ideal for structural applications including decking frames, floor ...

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£17.90
£17.90 - £17.90
£17.90
£10.08 - £14.94
£10.08 - £14.94
£10.08
Save up to 44% Save %

1.25M x 82 x 82mm Redwood Chamfered Decking Post Newel

£13.14 - £13.14
£13.14
£13.14 - £13.14
£13.14
In stock

1.25M x 82 x 82mm Redwood Chamfered Decking Post Newel Enhance your outdoor space with the 1.25M x 82 x 82mm Redwood Chamfered Decking Post...

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£13.14 - £13.14
£13.14
£13.14 - £13.14
£13.14

Redwood Decking Fillet Treated 4.2m x 45 x 12mm

£3.60 - £3.60
£3.60
£3.60 - £3.60
£3.60
In stock

Redwood Decking Fillet Treated 4.2 x 45 x 12mm

£3.60 - £3.60
£3.60
£3.60 - £3.60
£3.60

Redwood Decking Handrail Treated 4.2 x 75 x 33mm

£12.24 - £12.24
£12.24
£12.24 - £12.24
£12.24
In stock

4.2M x 75 x 33mm Redwood Decking Handrail Treated

£12.24 - £12.24
£12.24
£12.24 - £12.24
£12.24

Redwood Decking Spindle R4A Treated

£2.28 - £2.28
£2.28
£2.28 - £2.28
£2.28
In stock

42*42*900mm Redwood Decking Spindle R4A Treated

£2.28 - £2.28
£2.28
£2.28 - £2.28
£2.28

Redwood Decking Baserail Treated 4.2 x 78 x 38mm

£12.24 - £12.24
£12.24
£12.24 - £12.24
£12.24
In stock

4.2M x 78 x 38mm Redwood Decking Baserail Treated

£12.24 - £12.24
£12.24
£12.24 - £12.24
£12.24

Alter Supplies & Contracting

4.9

93 reviews on

Write a Review
Caroline Clulow
September, 2025
This may sound crazy but, honestly, I've never had such good service. Young men, mostly, who were knowledgeable and so helpful. Don't google for wood, most places are very expensive. Pieces that were £15 on Google were £4 here. 1.8 metre slats at £1.20. Great company.
George Davies
August, 2025
Friendly polite staff nothing to much trouble fast home delivery service would recommend to everyone
Adam Plenderleith (RevRev)
August, 2025
Another delivery from Alter Supplies today. Amazing service even for a relatively small order. Timber and slabs delivered promptly by a very cheery young man! An easy 5* given!
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