A king box spring is almost always built as two split halves (each 38″ × 80″ — the same footprint as a Twin XL) that sit side by side under your king mattress (76″ × 80″). The split design makes a large king foundation easy to deliver, carry up stairs and set up, and it's exactly what a split-king adjustable base needs so each side can raise and lower independently. Shop split king box springs and foundations matched to Sealy, Serta, Beautyrest, Simmons, Stearns & Foster and more — free delivery across Canada. • What it is: a king box spring built as two 38″ × 80″ halves (each a Twin XL footprint) • Together they support a standard king mattress (76″ × 80″) • Easier to deliver and carry up stairs than a one-piece foundation • Required for split-king adjustable bases (each side adjusts independently) • Brands: Sealy, Serta, Beautyrest, Simmons, Stearns & Foster, Springwall, Galaxy & NM • From $176 — free Canada-wide delivery
These mattresses feature a black or dark-tone cover — and since that cover sits under your sheets, colour won't change how you sleep. To find the right bed, shop by size (twin to king), comfort (plush, medium, firm), or type (memory foam, hybrid, pocket coil). Looking for the Beautyrest® Black® collection? That's a premium brand line, not a colour — browse it on the Beautyrest Black page. Every mattress includes a 365-night sleep trial and free delivery across Canada.
These mattresses feature a grey or neutral-tone cover — and since that cover sits under your sheets, colour won't change how you sleep. To find the right bed, shop by size (twin to king), comfort (plush, medium, firm), or type (memory foam, hybrid, pocket coil). Every mattress includes a 365-night sleep trial and free delivery across Canada.
Loading recommendations...

All Brands

Our entire selection of name brands.

Beautyrest logo Beautyrest (297) Chirofoam logo Chirofoam (39) Evergreen logo Evergreen (50) HealthGuard logo HealthGuard (76) Leggett & Platt logo Leggett & Platt (33) Marshall logo Marshall (57) Mlily logo Mlily (88) Natura logo Natura (44) NM logo NM (247) Sealy logo Sealy (171) Serta logo Serta (321) Serta iComfort logo Serta iComfort (84) Sinca logo Sinca (10) Springwall logo Springwall (244) Stearns & Foster logo Stearns & Foster (48) Tempur-pedic logo Tempur-pedic (81)

Upgrade your sleep at National Mattress

Discover a mattress that transforms your sleep into a truly rejuvenating experience. We offer a wide variety of options to suit every sleep style and preference, ensuring a better night's sleep.

Why Choose Us?

  • Variety: From plush to firm, we have options for every body type and sleep style.
  • Quality: Trusted brands and top-notch materials for long-lasting comfort.
  • Sleep Trials & Warranties: Enjoy peace of mind with flexible trials and warranties.
  • Expert Advice: Get personalized recommendations from our sleep specialists.

Mattress Selection Includes

  • Memory Foam: Contours to your body for personalized comfort and pressure relief.
  • Hybrid: Combines responsive springs with foam for balanced support and comfort.
  • Innerspring: Provides firm support, bounce, and cooling airflow.
  • Latex: Hypoallergenic, eco-friendly, and exceptionally comfortable.
  • Adjustable Beds: Customize your sleep position for optimal comfort.
Clearance Mattresses

Clearance Mattresses

Explore our discounted mattress collection, featuring limited quantities, floor models, and more.

Shop All Clearance

Mattress Selector

See which mattress is best for you!

Try Now

Thousands in Stock

We have over 1,000 mattresses in stock.

Shop Now
Loading recommendations...