Platform decks

Why platform decks are cheap. Shorter posts, simpler framing, no guard, usually no stairs. Compare $10 to $30 per square foot against $25 to $50 for a raised deck and $30 to $60 for a two-story. On a 240 square foot deck that's thousands of dollars of difference for the same usable area.

No ledger, no ledger problem. Freestanding decks avoid the attachment to the house entirely, which sidesteps the failure mode that causes the most serious deck collapses. That's genuinely useful on older houses where the floor framing is thin band board, I-joists, or metal-plate-connected trusses that may not accept a standard ledger attachment.

The catches. Ground-level decks sit close to soil and moisture, so decay resistance and ventilation matter more, not less. All lumber in contact with the ground must be approved preservative-treated wood suitable for ground contact. Footings still apply — bearing on undisturbed soil at least 12 inches below grade or below the frost line, whichever is deeper — and footings within 5 feet of the house foundation wall must bear at the same elevation as the house footing.

Permits still apply. Some jurisdictions exempt small low decks and many don't. Permits are $100 to $500. Call your building department; don't assume a low deck is unregulated.

How to choose

Stay under 30 inches if you can

That's the threshold where a guard becomes required, and guards are expensive at $30 to $210 per linear foot.

Use ground-contact-rated lumber

Anything touching soil must be approved preservative-treated for ground contact. This is not the place to save.

Keep airflow underneath

Low decks trap moisture easily. Solid skirting on a ground-level deck is asking for rot at $300 to $5,000 to repair.

Still call the building department

Exemptions for small low decks are local and inconsistent. Permits are $100 to $500 and the call is free.

Watch footings near the foundation

Within 5 feet of the house foundation wall, footings must bear at the same elevation as the house footing.