Treated Timber Supplies UK – Pressure-Treated & Structural Timber | Supreme Merchants

Get built for the long haul with our treated timber range. At Supreme Merchants, we supply pressure-treated, structurally graded softwood timber for both external and internal applications. Whether you’re specifying timber for load-bearing frames, decking supports, or landscaping sleepers, our treated timber offers superior resistance to rot, fungi, moisture and insect attack. Delivered UK-wide, with trade pricing, volume deals and nationwide dispatch.

What’s in this category

• Structural treated carcassing timber (C16, C24 grades) for framing, floor joists, roof timbers
• Treated timber boards & battens for external works – decking, sub-frames, joists
• Garden & landscaping treated timber – sleepers, retaining wall timber, timber posts in ground contact
• Timber for external facades, cladding and above-ground weather-exposed use
• Various lengths and cross-sections to fit trade and DIY jobs

Filter

Applications – where treated timber really works

  • Pressure-treated timber for decking and external use
  • C16 and C24 structural timber for stud walls and load-bearing projects
  • CLS timber for framing and internal work
  • Sawn & planed timber options

FAQ

Q: Can I use untreated timber outdoors?
A: You can, but it will degrade faster. Treated timber offers much better resistance to rot, fungi and insect attack through exposure.

Q: What does “treated” mean exactly?
A: It typically means the timber has been pressure-impregnated with preservatives under vacuum/pressure, ensuring the chemicals reach deep-into the fibres — giving long-term protection.

Q: How do I know which Use Class I need?
A: Consider how/where the timber sits: Ground contact or constant damp → UC4; External above ground → UC3; Internal occasional damp → UC2. Ask us if you’re unsure.

Q: Do I need a certificate or proof of treatment?
A: Yes — in commercial builds you should specify timber treated to BS 8417 and ask for the treatment certificate. Always check with your supplier.

Q: What lengths and sizes do you stock?
A: We stock a wide range of cross-sections (e.g., 47 mm × 100 mm, 75 mm × 150 mm etc) and standard lengths (2.4m to 4.8m+) — select your size in the filters above. For unusual lengths talk to our trade support.