The place for all your outdoor living space!
Your deck is only as strong as what’s holding it up. Structural materials – framing lumber, posts, beams, and foundation systems – are what keep every deck square, level, and safe for decades. At Premium Decking Supply, we stock the full range for residential and contractor builds across Chicagoland, ready for same-day pickup or delivery to your jobsite.
Structural Deck Materials
Three main categories covering every structural component your build requires. Click any subcategory to explore products & specs.
Framing Lumber & Timber
The skeleton of your deck – the joists, ledger boards, rim boards, and blocking that carry every pound of load from the surface down to the posts. Pressure-Treated (PT) lumber is the standard for most residential builds, resisting water, bugs, and rot even in ground-contact applications. KDAT lumber takes it a step further – kiln-dried after treatment so it arrives straighter and warps less on the job. For builds where wood rot isn’t an option, Galvanized Steel framing handles long spans with zero organic material to decay, while Aluminum framing gives you the same rot-free performance at a fraction of the weight – ideal for rooftop decks and docks. OC Dimensional lumber is the premium option – higher-end structural lumber for builds where finish quality and appearance matter on exposed framing elements.
Posts & Beams
Posts transfer your deck’s full load from the beams down to the footings. Beams span horizontally between posts and carry the weight of every joist above. 4×4 posts work for low decks under 6 feet, but the industry has largely moved to 6×6 posts as the standard for elevated and heavy-load builds – they resist bowing under sustained load and are increasingly required by code. If you’re building with a metal framing system, steel posts and aluminum posts keep the entire structure consistent — zero rot, zero warping, full system integrity from footing to joist. For premium builds where finish quality matters on exposed applications, OC posts are the higher-end option. For beams, drop beams are the simpler and most common configuration with joists resting on top, while flush beams run at joist height for more clearance underneath. When you need longer spans at a shallower depth, LVL engineered beams are the right call – straighter, stronger, and more consistent than solid sawn lumber.
Deck Foundation
Where your deck meets the earth – and in Chicagoland’s freeze-thaw climate, this decision matters more than most people realize. PierTech helical piers are ICC-certified steel shafts that screw below the frost line into stable soil – no digging, no curing, same-day build capability, with load ratings from 15,000 to 50,000 lbs per pier. Concrete tube forms are the traditional, budget-conscious option available in 8″, 10″, and 12″ diameters – solid on stable soil when schedule flexibility isn’t a constraint. Both systems pair with post anchor hardware including J-bolts and adjustable bases, and we carry concrete mix and accessories for tube form builds.
Water Resistant
Pressure-treated lumber is chemically treated to repel moisture – it won’t swell, saturate, or degrade when exposed to rain and ground contact.
Bug & Pest Resistant
The chemical preservatives in PT and KDAT lumber make it hostile to termites, carpenter ants, and wood-boring insects that destroy untreated wood.
Rot & Decay Resistant
Treated framing resists fungal decay that breaks down untreated wood within a few seasons of outdoor exposure.
Galvanized Steel – Zero Rot
Steel framing is hot-dip galvanized, meaning it carries no organic material that can rot, warp, or shrink – ever. Holds its dimensions for the life of the deck.
Aluminum – Lightweight & Corrosion-Free
Aluminum framing won’t rust, rot, or corrode – and it weighs a fraction of steel, making it the right pick for rooftop decks, docks, and weight-sensitive builds.
Freeze-Thaw Stable Foundation
PierTech helical piers anchor below the frost line in stable soil – so Chicagoland’s freeze-thaw cycles can’t heave, tilt, or crack your foundation the way they do with shallow concrete.
High Load Capacity
Helical piers are rated from 15,000 to 50,000 lbs per pier – engineered and ICC-certified to handle residential and light commercial deck loads without question.
KDAT – Kiln-Dried, Stays Straight
Kiln-Dried After Treatment lumber has most of its moisture removed post-treatment – so it arrives straighter, lighter, and far less likely to warp, twist, or shrink as it dries on the job.
Buying Structural Deck Materials?
We make it easy to source every structural component your deck frame needs in one place. Whether you’re a contractor running multiple builds or a homeowner tackling your first deck, we stock the right material at the right spec – and we’ll help you figure out which one that is before you order.
We’re Chicagoland’s largest deck display showroom – which means we actually stock what we sell, and our team uses this stuff every day. When you ask about post sizing or beam spans, you’re getting an answer from someone who’s spec’d hundreds of local decks, not someone reading off a product sheet.
Framing Lumber
Pressure-treated is still the most cost-effective framing option for standard residential builds. Works great when properly detailed with joist tape and post bases to keep it off direct moisture contact.
Posts & Beams
We always recommend 6×6 posts for anything over 6 feet high. The cost difference over 4×4 is minimal; the structural margin it gives you is not. LVL beams are worth the upgrade on any span over 10 feet.
Foundation
Our go-to foundation recommendation for any elevated deck in Chicagoland. Same-day installation and freeze-thaw stability alone justify the cost premium for the vast majority of customers we work with.
A drop beam sits below the top of the posts so joists rest directly on top – simpler install, most common for residential decks. A flush beam runs at the same height as the joists with joists connected to its face using joist hangers. Flush beams give you more clearance underneath and a cleaner profile, but require more precise installation.
Anything within 6 inches of the ground or in direct contact with it requires pressure-treated lumber by code in most jurisdictions. Above-ground framing in protected, ventilated positions may allow non-PT lumber depending on your local code – but PT is still the right long-term call for outdoor exposure. Steel and aluminum framing systems skip the rot question entirely.
6×6 is now the industry standard for most elevated decks and increasingly required by code for decks over 8 feet high. 4×4 posts work for low decks under 6 feet, but they bow under sustained load on taller builds. For hot tubs, multi-level structures, or anything more than 8 feet off the ground, 6×6 is the right spec.
For most Chicagoland builds, yes. Freeze-thaw cycles here are tough on concrete footings – shifting, cracking, and heaving within 5-10 years is common. PierTech helical piers anchor below the frost line in stable soil, install the same day, and let framing start immediately. The higher per-unit cost often pays for itself in reduced labor time and avoided future repairs. On stable soil with schedule flexibility and a simpler build, concrete tubes are still a solid, cost-effective option.
Most residential decks space posts no more than 8 feet apart, though the correct answer depends on your beam size, joist span, and local code. Tighter spacing – 6 feet – gives more margin for heavy loads. We can help you work backward from your deck dimensions to figure out the right configuration before you order.
Yes, in most builds. Blocking prevents joists from twisting or buckling laterally and is required by code wherever railing posts attach to the frame – all four sides of each post connection need it for a compliant, secure attachment. Mid-span blocking is required for longer joist runs; check your local code for the specific threshold.