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Timber Decking Joists | Treated Joists for Garden Decking Frames

Shop our range of pressure-treated timber decking joists, ideal for building strong and long-lasting decking subframes. Designed to support softwood and composite decking boards, these structural timbers are treated for outdoor durability and ground contact.

✅ UC3-treated for exterior use
✅ Available in popular sizes: 47x100mm, 47x150mm, 47x200mm
✅ Ideal for ground-level and raised decking projects
✅ Compatible with all major decking board types
✅ Strong, stable, and easy to install

Perfect for garden decking frames, outdoor platforms, and step construction. Trusted by landscapers, joiners, and home DIYers across the UK. Nationwide delivery available on all decking joists and framing

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

Alter Supplies
£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 %
Save up to 68% Save %

Timber - Regularised 75 x 47 (16ft x 3 x 2) Rail KD C24

Alter Supplies
£10.74
£10.74 - £10.74
£10.74
£3.46 - £8.22
£3.46 - £8.22
£3.46
In stock

75mm x 47mm Regularised C24 joist @ 2.4m, 3.6m, 4.8m long, pressure treated green, dressed, kiln dried. Used for general construction purposes

£10.74
£10.74 - £10.74
£10.74
£3.46 - £8.22
£3.46 - £8.22
£3.46
Save up to 68% Save %
Save up to 41% Save %

Regularised 125 x 47 (5 x 2) Joist KD C24 in 4.8m & 3.6m

Alter Supplies
£17.90
£17.90 - £17.90
£17.90
£10.54 - £13.70
£10.54 - £13.70
£10.54
In stock

125mm x 47mm Regularised C24 joist @ 4.8m & 3.6m long, pressure treated green, dressed, kiln dried. Used for general construction purposes or d...

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£17.90
£17.90 - £17.90
£17.90
£10.54 - £13.70
£10.54 - £13.70
£10.54
Save up to 41% Save %
Save up to 23% Save %

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

Alter Supplies
£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...

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£16.07
£16.07 - £16.48
£16.07
£12.36 - £16.48
£12.36 - £16.48
£12.36
Save up to 23% Save %

Regularised C24 & C16 100 x 47 (4 x 2)

Alter Supplies
£6.42 - £10.96
£6.42 - £10.96
£6.42 - £10.96
£6.42
In stock

£6.42 - £10.96
£6.42 - £10.96
£6.42 - £10.96
£6.42

Regularised 2.4M x 95 x 47 (8ft x 4 x 2) Rail KD C16

Alter Supplies
£7.34 - £7.34
£7.34
£7.34 - £7.34
£7.34
In stock

£7.34 - £7.34
£7.34
£7.34 - £7.34
£7.34

C24 & C16 150 x 47 (6x2)

Alter Supplies
£9.60 - £21.42
£9.60 - £21.42
£9.60 - £21.42
£9.60
In stock

Discover the Versatility of C24 & C16 Timber Introducing our premium C24 & C16 150 x 47 (6x2) timber, designed for both structural...

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£9.60 - £21.42
£9.60 - £21.42
£9.60 - £21.42
£9.60