Extreme Joist H4
H4 Ground-Rated Joists for Low-Set Decks
Building a low-set deck straight over concrete, a patio, or a balcony? eXtreme Joist is an H4 treated, DAR primed pine joist made for exactly that, where a standard bearer-and-joist build sits too high or won’t fit. Because it is rated H4 for ground contact, it can be laid directly on the slab without the decay and insect problems that would destroy above-ground timber in that position. We stock it DAR primed in 44×44, 68×44, 88×44, and 138×44, ready to frame a deck close to the ground.
Why eXtreme Joist for Low Decks
The point of eXtreme Joist is height, or the lack of it. On a low deck laid over concrete or a balcony, standard bearers and joists stack up too tall and waste your finished floor height. H4 joists solve that: rated for ground contact and damp conditions, they lay flat and low against the slab and still resist fungal decay and insect damage where H3 timber would fail.
Pine handles the load, too. Though a softwood, it has high compressive and bending strength on par with many hardwoods, so it carries deck loads without fracturing, while staying light and easy to cut, which makes it a favourite for DIY deck builders. Every eXtreme Joist is double primed, increasing water resistance and extending the frame’s life outdoors.
What Goes With It
A deck frame needs corrosion-rated fixings. Use galvanised or stainless steel decking screws and joist brackets so the fixings last as long as the H4 timber. Lay the boards with treated pine or hardwood decking, and for the rest of the outdoor frame see the full external treated pine range. Adding stairs off the deck? Pair it with treated pine stringers.
Serving Sydney Tradies and Renovators
- Trade pricing and bulk quantities: Competitive rates on volume orders. Call 1300 554 775 for trade and project pricing.
- Delivered to site across Sydney: Sydney, the Blue Mountains, Wollongong, and the Central Coast.
- H4 ground-rated and double primed: Lays directly on concrete or patios for low-set decks, with added water resistance.
- Australian-owned family business: Western Sydney based. Real people, real stock, real advice.
Whatever the low deck calls for, we’ve got the joist.
Call 1300 554 775 or request a quote online and our team will help match sections and spacing to your deck.
Frequently Asked Questions
What is eXtreme Joist used for?
Framing low-set decks laid directly over concrete, patios, or balconies, where standard bearers and joists would sit too high. It is H4 treated for ground contact.
What is the difference between H3 and H4 for deck joists?
H3 is for above-ground exterior use, while H4 is rated for ground contact and damp conditions. Deck joists laid on or near a slab need H4, which is why eXtreme Joist is H4 treated.
Can I lay decking joists directly on concrete?
Yes, with H4 ground-rated joists like eXtreme Joist. They resist decay and insect damage in that position, where H3 or untreated timber would fail.
What sizes does eXtreme Joist come in?
DAR primed in 44×44, 68×44, 88×44, and 138×44. Deeper sections carry longer spans; call 1300 554 775 for help matching section to span and joist spacing.
Why is eXtreme Joist primed?
It is double primed to increase water resistance and extend the life of the deck frame outdoors, and it gives a consistent base if you choose to paint it.