The short answer first
Height changes almost everything except the boards you walk on. A ground level deck is mainly a fight against damp, still air and tight access under a low frame. A raised deck is mainly a structure problem: taller posts, firm bearing, bracing, guards and stairs. Both need footings sized for the load they carry, a plan for water, and a decision about whether the deck leans on the house or stands on its own. Get those points right and the surface choice becomes the easy part.
Ground level: beams low and air that barely moves
A ground level deck often sits on short posts, or on beams held close to grade on low supports. That closeness is the whole challenge. Rain splashes up from soil and paving. Leaves collect under the frame and hold moisture against joists. Air moves slowly in the shallow gap, so wood dries slowly after wet weather.
Drainage has to be planned before the frame goes down. The ground under the deck should fall away from the house and should not hold puddles under beams.
Access is the other limit. Once boards are fitted, there may be no room to crawl under and inspect posts, beam joints or footings. A builder should agree inspection points and leave removable sections where checks will be needed later. Our deck building page sets out how a frame is normally put together, because mistakes on a low build are hard to reach afterwards.
Raised: posts, bearing and height working together
On a raised deck, the frame stands well clear of the ground, so posts carry the load over a longer length and the whole structure can sway if it is not braced. The American Wood Council guide DCA 6, which covers single level residential wood decks, sets a minimum 6x6 post, with 8x8 posts allowing a deck height up to 14 feet in the cases covered AWC DCA 6 guide.
Bearing at each post matters as much as post size. Beams must have full bearing at posts, at least 1.5 inches on wood or 3 inches on concrete or masonry, and beams may no longer straddle posts and be carried by through bolts alone AWC beam attachment FAQ.
Guards, edges and the 30 inch line
Height decides whether guards are a choice or a requirement. Raised surfaces more than 30 inches above grade or a floor below need guards at least 36 inches high ICC guard rules.
Many ground level decks sit below that line, so guards are often not required. Edges and steps still matter. Steps down to the yard need even treads, a firm edge people can see, and a rail where the drop or the users make one sensible.
On a raised deck, guards run along every open edge, and the stair opening needs its own guard treatment. Plan guard posts and their fixings with the frame, not as an afterthought once boards are down.
Stairs, landings and getting underneath
A ground level deck may need only one or two steps, or a gentle slope at one edge. A raised deck needs a full stair, usually with a landing where the stair turns or meets the yard.
Open sides of stairs need guards at least 34 inches high, measured from the tread nosings, when the total rise is over 30 inches ICC guard rules.
Raised decks gain one clear advantage: usable space underneath. That space helps with inspection and repairs, since a person can stand or use a ladder to reach joists and beam joints. It can also hold a covered area. Our covered decks and pergolas page covers shade and shelter options.
Footings that follow load, not habit
Every deck, low or high, sends its load to the ground through its footings. DCA 6 joist spans assume 40 psf live load and 10 psf dead load, and its footing sizes assume 1500 psf soil bearing AWC DCA 6 guide.
Those figures explain why footing size is not one standard pad for every post. A post near the middle of a deck carries the load from a larger area of frame and boards than a corner post, so its footing needs more bearing area. Soft or filled soil carries less than firm natural soil, so the same deck can need larger footings on one site than on another.
Ask how each footing size was worked out, and expect an answer tied to load area and soil, not to habit.
Ledger or free standing at either height
Most decks are either fixed to the house on a ledger board or built to stand apart from it. DCA 6 draws a useful line between the two standalone forms: a non-ledger deck is vertically independent of the house, while a free standing deck is both vertically and laterally independent AWC DCA 6 guide.
A ledger deck uses the house for support on one side, so the ledger fixing and flashing carry a lot of responsibility. A free standing deck carries itself, so it needs extra posts near the house and its own resistance to sideways movement. Diagonal bracing adds stiffness to that kind of frame AWC DCA 6 guide.
Bracing placement is specific. Knee braces should only be installed at corner posts, not interior posts, because bracing adds lateral load and centre posts already carry more vertical load AWC knee brace FAQ.
Low decks near a house often suit a free standing layout, since it avoids cutting into wall finishes close to grade. If you are comparing sites, our guide to the areas we cover shows where DeckNear can make a referral.
Frequently asked questions
At what height does a deck need guards?
Surfaces more than 30 inches above the ground or a lower surface need guards at least 36 inches high. Open sides of stairs need guards too when the total rise is over 30 inches, and those stair guards must be at least 34 inches high measured from the tread nosings. Measure from the finished grade below, not from the deck boards.
Does a ground level deck still need proper footings?
Yes. Low decks still carry people, furniture and snow loads down through beams and posts to the ground. Footing size follows the load each post carries and the bearing strength of the soil below. A low height does not remove that load path. It only makes the footings harder to see and check once the frame is built over them.
Why are knee braces fitted only at corner posts?
Knee braces add lateral load as well as stiffness. Guidance from the American Wood Council says knee braces should only be installed at corner posts, not interior posts, because centre posts already carry more vertical load than corner posts. Adding brace loads to a heavily loaded middle post works against the structure instead of helping it stay steady.
What is the difference between a non-ledger deck and a free standing deck?
A non-ledger deck is vertically independent of the house, so it carries its own weight on its own posts and footings. A free standing deck goes one step further and is both vertically and laterally independent, so it also resists sideways movement on its own. The second type needs its own bracing plan rather than relying on the house wall.
Sources
Common questions
At what height does a deck need guards?
Surfaces more than 30 inches above the ground or a lower surface need guards at least 36 inches high. Open sides of stairs need guards too when the total rise is over 30 inches, and those stair guards must be at least 34 inches high measured from the tread nosings. Measure from the finished grade below, not from the deck boards.
Does a ground level deck still need proper footings?
Yes. Low decks still carry people, furniture and snow loads down through beams and posts to the ground. Footing size follows the load each post carries and the bearing strength of the soil below. A low height does not remove that load path. It only makes the footings harder to see and check once the frame is built over them.
Why are knee braces fitted only at corner posts?
Knee braces add lateral load as well as stiffness. Guidance from the American Wood Council says knee braces should only be installed at corner posts, not interior posts, because centre posts already carry more vertical load than corner posts. Adding brace loads to a heavily loaded middle post works against the structure instead of helping it stay steady.
What is the difference between a non-ledger deck and a free standing deck?
A non-ledger deck is vertically independent of the house, so it carries its own weight on its own posts and footings. A free standing deck goes one step further and is both vertically and laterally independent, so it also resists sideways movement on its own. The second type needs its own bracing plan rather than relying on the house wall.