Just what is a “freestanding” deck? Some freestanding decks are obvious – they are standing alone in the yard.
But many freestanding decks do not stand alone but are indeed right next to a house. They seem to be attached to the house, and they may be attached superficially. What makes a deck truly freestanding is that it is self-supporting. It does not use the adjacent house for support. It stands “free” of attachment. Here’s a simple side view of a deck:
Structurally, the house supports half the weight of the deck (including its furniture and people), and the beam and columns at the end support the other half:
— unless the deck is self-supporting (freestanding). Add another beam and columns near the house, and the deck puts no weight on the house.
Here’s a normal deck, seemingly attached to its house:
But look below that deck, and you can see its additional structure.
Indeed, why would someone want her¹ deck freestanding? That extra structure, especially the extra columns and footings, adds cost.
Building Codes offer one reason. According to the International Residential Code², adopted by most states, a deck does not need a building permit if it is “less than 200 square feet, under 30” off the ground, does not serve a required exit door, and is not attached to the dwelling“ — if it is freestanding.
A more common reason: deck builders freestand a deck when the house structure or materials do not allow solid attachment. For example, the cantilevered (“overhanging”) side of a house will not properly support a deck.
And consider a fieldstone foundation: there is no practical way to attach a deck to irregular fieldstone.
Brick veneer walls also lack the lateral strength to support a deck. Even hollow concrete presents fastening challenges. Houses with wood I-joists or only studs at deck level can be enhanced to bear the weight of a deck, but these “structural enhancements” often prove impractical, too expensive, or too difficult to verify.
So, add another beam and more columns and footings. Even include a few screws to “attach” the deck to your house, if you want. They will not transfer significant weight to your house. Then your deck is solid. Right?
Actually, No. You’ve supported the deck load vertically — it will not collapse under the weight of people and furniture. But you’ve not addressed lateral and horizontal stability. Without any solid attachment a house, your deck will sway and wobble. It needs bracing, especially if it is high off the ground.
The type, location, and attachment of those braces is complex; indeed, they are beyond my scope here. But I have written in detail about bracing freestanding decks in The Journal of Light Construction, the widely respected construction magazine.
For a thorough explanation of Post and Beam construction, see my article, What is Post and Beam and Why would your Deck Care?
For an explanation of other deck terms, see my earlier blog article, Can’t Understand Your Deck Contractor? .
- I use female pronouns generically. Literature has too long touted male pronouns.
- IRC 2009, para. R105.2.
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Very well-written sir! Informative and detailed- much appreciated!
In NY all decks require a permit. Even freestanding decks, under 200 sq. ft. not attached to rear door.
Note: your state may not have a maximum size without permit – PA does not. So, as long as we keep it under 30″ high, the thing can be just huge. Thanks for your site – it is useful.
Jeff, thanks for your comment. You are correct, states and individual localities can override IRC requirements. We recently applied for a permit for a low deck attached to a house in a local town. That Building Inspector did not care about the deck’s attachment. Any deck in his town under 12″ high does not require a permit, regardless of size. He noted that the consequence of a deck under 12″ high collapsing would be minor. No one would be injured. OK, but we still built a solid deck that met all other code requirements.
Many Towns , when in a flood zone, ask for a freestanding deck when house does not comply with FEMA elevations.
Also, a caution. Many Towns require that any footing within 5′ of a foundation/basement wall, require the footing to go down to the depth of the basement footing. The load spread could impact the basement wall. If the house foundation is 8′ below grade, it is a long tough dig for a footing.
Good point, Rick. Thanks.