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I don't want the deck attached to the house. I was thinking free standing. This would remove any flashing needed and leaks etc. Any ideas or suggestions or, reasons this is not a good method?

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    How are you going to do five-foot deep footings that are three feet in diameter, zero feet away from your house?
    – Mazura
    Commented Jun 19, 2021 at 20:41
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    @Mazura -- one way to solve it is to move the inner footings away from the house, cantilevering the portion of the deck closest to the house as a result Commented Jun 19, 2021 at 20:51
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    I have built entire decks that were freestanding on pier blocks (for Mobil/modular homes). The height of the deck also makes a difference with bracing. Check your local requirements as my area requires the deck to be attached at doorways incase of an earthquake so the egress will not separate.
    – Ed Beal
    Commented Jun 19, 2021 at 21:35

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There is nothing in the Building Code that requires a deck be attached to the house.

However, if it is, then the Code requires at least two steel straps near the ends of the deck and attached to the foundation or floor joists.

If you live in a seismically active area or high wind area we know the deck will move differently than the house during an “event”.

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  • I agree, for a few years if the deck has a small separation from the house that provided a loophole and less electrical was required.
    – Ed Beal
    Commented Jun 19, 2021 at 21:32
  • Is it a problem if they move differently during an event? Commented Jun 20, 2021 at 3:42
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    @FreshCodemonger Yes, it’s a problem because they crash into each other and one (usually the light one) gets torn apart.
    – Lee Sam
    Commented Jun 20, 2021 at 5:30
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I've built two decks like this.

One I did pt-6x6 posts epoxy bolted into the basement concrete wall. This was pseudo free standing as the posts are attached to the house. The PSL beam that sits on the posts was not (tho it attaches to the posts). There is a 1" gap between the deck and the exterior of the house.

The other one I did concrete columns with offset footings less than 2' off the ground. You can cantilever joists and beams to position the closer footings to the house structure.

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PORCH DESIGN & CONSTRUCTION GUIDELINES
www.chicago.gov, PDF.

"specific methods of lateral bracing are not considered, in detail, in these Design Guidelines." If the plans you submit to the city are approved, then no. Otherwise you have to do some math. The only thing that even mentions free standing is a stair case.

LATERAL BRACING – Is a system within the porch structure to prevent lateral movement such as racking and possible collapse. Many, if not most, porches rely on the buildings that they are attached to for lateral stability. Therefore, the porch structures must be securely attached to the main buildings through the ledger beams or other means. However, even with attachment to the main building the outstanding or free edge of the porch structure must be braced. This is especially true of stair structures that are constructed at the edge of the main porch platforms or decks. (See Drawing 1D for a plan of this type of porch.)

The forces that can cause racking of a porch structure are wind loads, vibration and impact from porch use and out of plumb framing. Because these forces can occur or impinge on any porch structure, every porch structure must be designed and constructed to include a lateral bracing system. The lateral bracing system must be designed to resist a lateral load equal to at least the wind load plus 2% of the gravity dead and live loads. The minimum wind load is defined as 20 pounds per square foot (psf) in the Chicago Building Code.

Lateral bracing is therefore most commonly found on the face of the porch structure that is parallel to the rear wall of the building. This is also considered to be the free edge(s) of the porch platform(s). X, K or inverted V bracing is commonly used for this purpose as are diagonal braces at the corners of posts and beams. The X, K or inverted V bracing carries the lateral load from the various levels of the porch to the ground.

As the building is typically considered adequate to provide some lateral support, no bracing is usually considered necessary to prevent movement perpendicular to the rear wall of the building. It is also possible, with some porch configurations, to brace the porch structure with diagonal bracing in the plane of the decks. If the porch decks are designed to act as horizontal diaphragms, then it is possible for the entire structure to be adequately braced using the stability of the building. Bracing of decks can be accomplished by the use of dimension lumber attached diagonally under the joists and beams. Furthermore, decks can be turned into diaphragms by installing the deck boards on a 45 degree angle.

Because of the multitude of porch configurations in the City of Chicago and many possible bracing configurations, specific methods of lateral bracing are not considered, in detail, in these Design Guidelines.

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