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 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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