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Old 04-10-2008, 06:58 AM   #1
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Decks -Beams vs Posts

Why are some decks built with post and beams and some with just posts in the corners?


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Old 04-10-2008, 07:38 AM   #2
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Size and economics are the reasons.


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Old 04-10-2008, 07:46 AM   #3
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If I were building a 16x12 freestanding deck that will be about 18 inches from the ground, would it be best to use beams or just posts in the corners?

Last edited by sandyman720; 04-10-2008 at 07:50 AM.
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Old 04-10-2008, 08:03 AM   #4
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Doubling the perimeter rim joists and running a beam down the middle of the span will eliminate any bounce in the deck.
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Old 04-13-2008, 09:30 AM   #5
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Posts support the beams which support the joists which support the deck boards.

If you omit the beams, you need to support the joists another way. Posts "in the corners" would support the joists directly by way of supporting the rim joist. This is the outer edge band that the joist tails get nailed to. It's also what your railing posts would be attached to (if you had any).

You will need a supporting beam in the middle of your 12' span. There's no way to use posts to support the joists themselves in a mid-span situation (unless you cut and hangered 6' joists off both sides of a mid-span rim joist...but that's just a REALLY bad idea).

For your outer joist support, you could double up your rim joist and install posts beneath that to support the outer edge. For that to work, your rim joist sizes would need to be adequate to span the gap between posts. Don't expect a doubled 2x6 rim joist to span 16'. Doubled 2x8s could span 8', so you'd only need 3 posts. When you "double" a rim joist, use exterior glue generously between the boards and nail them w/ 12d or 16d galvanized nails. Stagger your nailing pattern so you don't end up splitting the boards.

If you go that route, hanger your joists off the doubled rim joist. Use Simpson LUS hangers for your size joists. Make sure the hangers you get have a "Z" at the end of their product code. That means the hanger is galvanized and will hold up better against the pressure treated wood. Use 10d galvanized joist hanger nails (sometimes called Teco nails) for the hangers.


you could put a beam under the outer edge and use a single rim joist. One thing about that is you can "tuck" the beam back under the deck and cantilever the joists 1' to help hide the substructure.

That oughta at least get you started...

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