Hardwood Joists

Hardwood Joists for Sale in Ireland

If you are building a hardwood deck, the frame underneath should last as long as the boards on top. Our hardwood joists are a dense hardwood with natural oils and a tight grain that resist rot, insects and fungal decay without chemical treatment, so the substructure is not the weak point of your deck.

The joists are planed all over (PAO), so every face is smooth and square. That makes them easier to set out level and fix accurately, and neat enough to use where the frame is on show, around the edge of a raised deck or on steps.

Hardwood joist sizes

Choose the section by the height of the deck and the span:

• The 65×42 mm hardwood joist is a slim section for very low frames and bearers on a firm base.
• The 90×45 mm hardwood joist is a compact choice for low decks.
• The 190×45 mm hardwood joist is the deep main joist for longer spans and raised decks.

The span a joist can carry depends on its size, the spacing and the load, so have an engineer or a span table confirm the size before you build. Choose the length on the product page; a joist that runs the full width of the deck means no joints to support. The calculator on each product page works out how many joists you need.

Joist spacing

For a residential timber deck, space hardwood joists at a maximum of 400 mm centres. For heavier loads, close them up to 300 mm centres or less, and give the frame a slight fall so water drains away.

Hardwood decking joists vs other timber joists

Oak joists are the other hardwood option, heavy sawn at 70 mm thick and Durability Class 2. For a lighter softwood frame, see Ecowood joists or Douglas Fir joists. For the boards on top, see Yellow Balau decking and Yellow Balau boards.

Fixing hardwood joists

Dense hardwood needs more care than softwood when you fix it:

• Pre drill at every fixing point. In a timber this dense, a forced fixing splits the joist.
• Use A2 or A4 stainless steel fixings and hangers, never galvanised or mild steel, because the natural tannins in the timber react with them and stain. See our timber connectors and timber screws.
• Plan your lifts. A 190×45 mm hardwood joist is much heavier than the same size in softwood.

Looking after hardwood joists

Hardwood joists don’t need treating to resist rot, but exposed timber weathers to silver grey. Where the frame is on show, most customers oil it along with the deck to hold its colour, using a hardwood oil such as Deks Olje from our exterior wood oils. Seal any cuts and notches with an end grain preservative to keep moisture out of the exposed grain.

See every species in our timber joists range.