Deck posts

sannitig

This is going to be the first deck I've ever built and may be coming here a few times for some pointers.

I plan to have 3 posts dug 8'6" apart O.C. with a cantalever of 2 feet on each end. This would equal a total of 21' of beam.

What should I be using?
2-2x6?
2-2x8?

Or could I even use 3-2x6? I don't have much height to work with and I am hoping that 3-2x6 is just as strong if not stronger than 2-2x8.

The joists that will be going across are 16' and I will be doing them 16"oc, if that matters.

I would really like to use 3-2x6 as this would not cause the deck to be flush with the sliding door. Please checkout the attachment of the deck plans. The deck is only going to be a foot high and I was thinking of using saddles instead of 4x4 posts and placing the beam directly into the saddle. Thoughts?

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cortell

Assuming you're using southern pine, and many other things, you'll need to use 3-2x8 or 2-2x10 to meet code. Refer to
http://www.deckmagazine.com/pdf/2008/0805/0805stru.pdf

This assume your local building code does not have more restrictive code.

If you want to lower the height of the deck, use more posts.

sannitig

hey there thanks for your reply. I will be using spf pressure treated wood. I may not know much but 3 to buy eights seems a bit excessive no?

I know it's code but sends excessive none the less

cortell

Many think code isn't enough! One thing is for sure: you're out of your league to look at it that way. These numbers aren't pulled out of a hat. A lot of research and analysis has gone into determining span tables and code in general. Questioning code based on gut feeling is misguided, to put it kindly. And if you plan on pulling a permit to build this deck, it doesn't matter what your gut feeling is. You'll need to meet code even if you think it's excessive.

sannitig

Indeed. Thanks for the help

sannitig

sorry I forgot to ask do the specifications still apply if there are post along the middle as well?

if you look at the diagram there are 3 post at the edge of the deck and 3 post across the middle as well.

pardon the spelling and grammar this is done by a smartphone

cortell

Sure thing. BTW, note that SPF is not as strong as southern pine, so the sizes I quoted may not even work for you. Use the table in the article to find the appropriate beam spans for your deck.

cortell

You have a total of six posts--three per beam run. What I stated is based on that.

sannitig

thank you for the chart it is really good. my only question now which also relates to the chart, is, if you look at the joist spans that is from the wall to the first post correct?

since I have a post in between the span do I now have two spans at roughly 6-7 feet each? or is the joist spain still considered 1 span at 14 feet?

this would be a huge factor on to which beam I would build....

cortell

You have a joist span of 7'6" from the mid beam to the exterior beam. That is the longest joist span in your deck, and that is what I used to answer your question. You have shorter spans between the house and the mid beam, but you'll not want to take that into consideration since it would significantly complicate your design and not reduce the overall deck height you're trying to reach since it would have no effect on the exterior beam requirements.

I.e., just use 7'6" as your joist span when looking at the span table.

sannitig

Thanks. I really appreciate the help.

sannitig

Ok, like I said, I will be coming back here regularly during this project. I will be using the 3-2x8s to create the beam, as I want to keep the hieght low.

I have been looking online and the post brackets only seem to come in 4" and 6" at home depot.

Since my beam will be 3-2x8s which is 4.5" thick, how will I fasten is to the posts? I would like to use brackets and not angled nailing/nailing into end grain if possible.

Any suggestions? I found this manufacturer but there seems to be no sizes for my situation. Laminating 3 boards together doesn't seem that uncommon, there's got to be something out there...

http://www.strongtie.com/products/connectors/PC-EPC.asp

dpach

These are the ones I used and where I live, it passed code just fine.

I didn't read what size your posts are going to be; mine are 6x6 posts and these worked perfectly. Each post requires two; one for each side of the beam.

http://www.strongtie.com/products/co...e-lpcz-lce.asp

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GBrackins

sannitig,

I myself am not a fan of ground level decks. They typically have ventilation issues trapping moisture under the deck. The lower part of beams/joists tend to retain moisture which causes the wood to swell. The tops exposed to sun and air moving across the deck tend to dry out and as a result shrink. The differential moisture content tends to cause the wood framing members to cup and twist. A friend of mine did not heed my advice and built one. five years later he was having to repair it. When clients want me to design ground level decks I do my best in convincing them to construction a ground level patio. If you must have a wood working project then add a pergola or sunshade to the patio.

I see you're gotten a lot of imput. I'd like to add a few items. I have attached the "Prescriptive Residential Wood Deck Guide" http://www.awc.org/publications/DCA/DCA6/DCA6-09.pdf as published by he American Wood Council based upon the 2009 International Residential Code. This guide should answer most of your questions. It will provide tables for beams and joists.

I would check with you local building department and determine if a building permit is necessary for your project, and if they have an deck design guidelines. Some jurisdiction have a list of requirements you have to meet. If you build a deck and a permit is required (and you failed to obtain one) you can be fined, and at the worst be required to take down the deck. A few quick questions don't cost and can save you money.

I'm a little confused by your sketch. What size are the joists? I see you said 16' in length. You also stated you're using pressure preservative spruce-pine-fir?

Deck construction although fairly simple and straighforward must be done correctly. Deck collapses are common and often results in serious injuries. A lot of research has been done in the last few years in the proper construction of decks, and every three years additional requirements come on. I understand your's is a ground level deck. I'm making a blanket statement about decks in general.

__________________
Gary

"You get what you pay for, and sometimes free costs more!"

cortell

Very smart, dpach. You installed a membrane to prevent water penetration between members of the built-up beam.