Beam support for deck in U-shaped house

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Old 03-16-19, 10:36 AM
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Beam support for deck in U-shaped house

Hello - I'm trying to figure out how to make code-compliant footings for my deck that sits in a "U" shape area adjacent to my house. The issue I'm running into is the support beams will necessarily have to be perpendicular to at least one wall of the house. Can I attach the beams to the ledger boards? I'd really like to avoid digging down to foundation depth (there is also a drain tile that runs along the entire foundation here - I think that would interfere with footings right next to the house?). The light red area is the 5' from the foundation marker - any footings within that area have to go to depth of foundation. I could in theory make this a floating deck, because the deck is only 15" off grade, but that would still require footings next to house, which is considered disturbed soil. Any thoughts on how to avoid putting footings in the "red" area, and attaching the beams in a code-compliant manner to the ledger board would be greatly appreciated!

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Old 03-16-19, 11:21 AM
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Unfortunately, the answer we have to give is no, since that would create an unknown point load on the ledger that would probably exceed the amount of weight that can be put on those points of the ledger. That being said, most residential decks with special needs or unusual construction need to be designed and approved by a structural engineer. No one here can do that for you, so while we can give advice, we aren't going to be able to do what they can do.

However, a structural engineer can determine where piers would have to be located (how close to the foundation) so that the point loads on the ledger would not exceed maximum. We just can't say how close.

Don't want to scrap your design but it's often easier to have an interior concrete stem wall and bottom plate to take the place of beams, that is augmented by a few perimeter piers and beams. Then you have single joists attaching to the ledger on the entire perimeter, and they rest on the stem wall for support. A perimeter beam with piers supports the outside perimeter of the deck. Add perpendicular blocking wherever needed to maintain one direction for your decking.
 
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Old 03-16-19, 11:45 AM
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Ok thanks - I was afraid that would be the answer. Was hoping to avoid solutions that require a structural engineer, they aren't cheap!
 
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Old 03-16-19, 01:14 PM
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Depends how picky your permit office is. Something like this eliminates most of your beams, makes single joist connections at the ledger (with the exception of the hip joist which is doubled, but attached to a different ledger on either side... and with the concrete stem wall located 5 feet away, the hip-ledger attachment is only holding part of a 25 sq ft area) and would probably be easily constructed and approved without an engineer, provided the concrete stem wall is at least 5 feet from the structure, which is a common code.

Right click and open image in a new window to see it properly. Sorry for the messy drawing. I'm a volunteer.
 
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Old 03-16-19, 04:56 PM
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Thanks! My building department is notoriously picky...I'm thinking of keeping the beam, biting the bullet and digging down to the foundation a couple feet from the two walls, so I don't have any actual load on the house, except on the long wall with the ledger board. I'd rather dig three deep footings than dig a whole stem wall. What should I do about the drain tile though? I know that there is one running around the whole section of the house there - is that going to cause me issues when I dig down?
 
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Old 03-16-19, 05:09 PM
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I would assume it will cause you problems, yes. Only other idea I would have is a foundation pocket for your beams. Your ledger would then fit between the beams. You would need to flash the perimeter very well.
 
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