Deck build Issue

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Old 08-05-14, 09:31 AM
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Deck build Issue

I wanted to have a deck build in my backyard. I live in a row home in Philadelphia. We bought all of the materials already and it can't be returned since it was a special order. The deck size will be 14x15 feet above ground.

The footing of the deck should go 30" below the ground. The two holes away from the house are good but the two closet to the house is only 24" deep. We can't dig any further because we hit the foundation of the house. Can we use the foundation and have the footing sit on top of the foundation? We would be pouring cement into the hole once we are finished. Would that be safe? I was thinking if the foundation can support the house then it can support the deck but I'm not sure. Please help, I'm not sure if I want to have to work continued.
 
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Old 08-05-14, 02:05 PM
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As I see it, you have 2 options: Either increase the cantilever of the joists supported by the beam closest to the house (meaning you need to dig 2 holes farther away, separating them from the house footings), or consider attaching the deck to the building using a ledger board. Both options mean filling in the 2 shallow holes and not using them.

Your local AHJ may have additional requirements, so you need to contact them for advice before you work up plans and apply for your building permit.
 
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Old 08-05-14, 02:05 PM
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Welcome to the forums! Is this a free standing deck? I question only two posts for a deck that size. Any pour against the house must be at the same level as the house's footing, so you may have to move outward on your close in footings to accomplish this. For good reference, here is some very valuable information. See section 9 for an explanation. http://www.awc.org/publications/dca/dca6/dca6-09.pdf
 
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Old 08-05-14, 02:12 PM
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Do you have a permit for this deck? Your building inspections dept should be able to provide you with guidance as to what they expect to see for approval.
 
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Old 08-08-14, 08:09 AM
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I do have a permit but the inspector said the footing closest to the house has to be 30" deep. We dug the hole and at 24" we hit the foundation to the house. The inspector said since we can't dig beyond 24", the deck will have to be supported by the house itself by drilling in metal rods into the house under the kitchen floor. I asked a contractor about it and it would cost $3K+ just to do that! I can't afford the additional cost. I see a bunch of decks in the neighborhood that I know didn't request for a permit to build a deck. Can I just have the footing of the deck sit on top of the foundation? If the foundation can support the house I would think that is can support the deck. I would pour cement and fill in the hole. The only reason it has to be that deep is because the frost line but if the footing is on the concrete foundation of the house with cement around it would that be okay???
 
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Old 08-08-14, 09:01 AM
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Not sure why the inspector didn't tell you to move your holes out 6 or 8" so your hole would bypass the foundation footing. Then you could accomplish the 30" he required. Cantilevering behind the posts is a non issue. Also not sure what "rods" he was referring to. Is your kitchen above grade?
 
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Old 08-13-14, 07:55 AM
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The inspector said the footing can't be more then 2 feet away from the house because it would be unstable. the rods he was referring to had to be go thru the support beams of the house and those beams were right under the kitchen.

I really don't know what to do anymore. I thought cemeneting the footing to the foundation of the house would be the safest option but I'm really not sure.
 
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Old 08-13-14, 09:12 AM
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I assume they are talking about bolting a sill plate to the edge of the house so you don't need the posts & footers next to the house. How difficult and expensive it is will depend on your house. Since you're hitting the house's footer at 24" I assume you have a crawl space that will give you access to rim joist to through bolt the ledger to the house.

In my area the inspectors really want through bolts and not lag bolt if there is any way possible. They must be hot dip galvanized and a minimum of 1/2" diameter. Make sure you pay attention to the flashing because if done incorrectly you can have water and rot issues where the deck meets the house.

 
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Old 08-13-14, 09:12 AM
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I assume they are talking about bolting a sill plate to the edge of the house so you don't need the posts & footers next to the house. How difficult and expensive it is will depend on your house. Since you're hitting the house's footer at 24" I assume you have a crawl space that will give you access to rim joist to through bolt the ledger to the house.

In my area the inspectors really want through bolts and not lag bolt if there is any way possible. They must be hot dip galvanized and a minimum of 1/2" diameter. Make sure you pay attention to the flashing because if done incorrectly you can have water and rot issues where the deck meets the house.

 
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Old 08-13-14, 02:21 PM
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Pilot,

I agree on the preference for through-bolts instead of lag bolts. However, DCA 6 does allow both lag bolts or through-bolts to be used for attaching ledgers. Even though I've found the use of lags to be a bad practice--every single deck I've inspected since the late 80s (probably close to 50) that had ledger boards or railing posts fastened with lag bolts, had loose lag bolts. Many were capable of being tightened a complete revolution, some more, using a 3/8"-drive ratchet/socket combination. Through-bolts rarely were loose, but if so, usually just a fraction of a revolution from being tight.

The detail you included is a bit misleading, and slightly problematic. I've only seen copper flashing once or twice during more than 30 years of inspections, on high-end houses. Maybe it's a regional thing. Galvanized steel is more common, and recently, self-adhesive polymers. But more seriously, the detail shown isn't a good one, as it tends to dump and trap dirt and water between the vertical face of flashing and the first deck board (which overlaps the ledger). It's much better to install a deeper ledger than the joists, making the top of it even with the finished deck planks. That way, the flashing dumps water into the open space between the flashed ledger and the first deck board, minimizing the chance for entrapment and rotting of that deck board edge.
 
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