16x20 Deck Design

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Old 04-04-08, 04:36 PM
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16x20 Deck Design

I am working on the design for a 16x20 deck. The surface will be about 7 foot off the ground. 20' is the length that runs against the house, except that the ledger is only 14' and 10".

Since I will have 6' hanging off the end (due to the 14' ledger) do I need to add a post or two a foot or two from the house?

Also, I want to do this with only one beam if possible, but I want it to be stable. I live in MN and we get heavy snow too. Assuming I use 10" beams, what size post & joists do I need to do this with a single beam?

I've been poking around with Lowe's designer, but it's difficult to change the options (have to restart and redo it a dozen times to figure out what I want to do!). Is there a better software application for weighing the options?

Thanks!
 
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Old 04-04-08, 04:53 PM
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16x20 Deck Design

Your biggest problem is trying ti use a ledger attached the house. Free-standing is a much better choice since once you pentrate your exterior moisture barrier (not the siding), you are asking for problems.

Big water, leakage and mold problems all because you think you might savea penny or two. A ledger is very difficult to seal, flash and waterproof even after you have installed and properly sealed the through bolts (never lags).

Since you live in MN, you can appreciate the snow, ice and moisture problems. If you are in the civilized part of the state, you may be able to get good standard details.

Posts - 4x4 or 6x6 (preferred). Foundations - Sonotubes (48" minimum deep) with Simpson connectors embedded to connect the posts.

Dick
 
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Old 04-04-08, 05:28 PM
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The house is about 3 years old and the 14' ledger was included during construction...
 
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Old 04-04-08, 05:45 PM
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16x20 Deck Design

You are building something that was not designed for when the house was built. Apparently you are only concerned with the vertical loads.

Even if the ledger was the right length, a ledger is still a bad way to go. You will still have to do some flashiing to shed the water.

Keep the deck separate from the house. - Better, easier and cheaper in the end.
 
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Old 04-05-08, 06:50 AM
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I will look at free standing, but I think my question has been misunderstood.

Assuming I do free standing, the lowes design now calls for 3 beams. My question is basically, what size wood can I safely use to eliminate that middle beam? I've tried several options on Lowes and none of them design it without that middle beam. My desire for no middle beam is basically simplicity and somewhat visual. I am not trying to diminish the quality, I just want to know how/if it can be done.
 
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